QM 2011 - XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collisions
2011 5 22 - 2011 5 28 Centre Bonlieu
ii Contents
Tagging of eta decay products in Bose-Einstein correlations to analyze chiral restoration 1
Equation of state and initial temperature of quark gluon plasma at RHIC ...... 1
The phase diagram in T-mu-Nc space ...... 1
Soft-quark bremsstrahlung and energy losses ...... 2
On the fluctuation-dissipation theorem for soft fermionic excitations in a hot QCD plasma 2
Next-to-leading order structure function for DIS off a large nucleus ...... 3
Higher harmonic jet tomography as a probe of fluctuating initial condition geometries in A+A ...... 3
Flow-Driven Conical Correlations in Heavy-Ion Collisions ...... 3
The Single Flavor Color Superconductivity in a Magnetic Field...... 4
The Subleading Term of the Strong Coupling Expansion of the Heavy-Quark Potential . 4
Mach Cone Induced by γ-Triggered Jets in High-Energy Heavy-Ion Collisions ...... 5
The second act of hydro: shocks and sounds from initial perturbations andjets ...... 5
Viscous QCD matter at RHIC and LHC energies. Insights from viscous hydrodynamics + hadron cascade hybrid approach ...... 5
Non-Extensive Approach to High-Energy Collisions ...... 6
Momentum broadening in weakly coupled quark-gluon plasmas ...... 7
Radial and elliptic flow in LHC Pb+Pb collisions from viscous hydrodynamics ...... 7
Direct Photons from microscopic+macroscopic hybrid model ...... 8
Massive QCD antenna radiation in medium ...... 8
The QGP shear viscosity: elusive goal or just around the corner? ...... 8
Jet shower evolution in medium and di-jet asymmetry in PbPb collisions at the LHC . . 9
Experimental study of quark and gluon jets in proton-proton and heavy-ion collisions. . 9
iii Simulations of thermodynamic and kinetic properties of the strongly coupled quark-gluon plasma ...... 10
Direct jet reconstruction in d+Au collisions at PHENIX ...... 11
Upsilon production at RHIC and LHC ...... 11
Non-extensive Statistical Approach to Fragmentation ...... 11
Equilibration and Thermalization of Strongly Coupled Field Theories ...... 12
Strong Coupled Pion Superfluid ...... 12
Bulk properties of PbPb collisions at the LHC measured by ALICE ...... 13
Common discussion with 3 speakers ...... 13
Anisotropic flow from ALICE ...... 13
Flow measurements from the CMS experiment ...... 14
Quenching of single hadron and photon spectra from RHIC toLHC ...... 14
Particle production at large transverse momentum with ALICE ...... 14
Monte Carlo tools for jet quenching ...... 15
STAR on reconstructed jets and jet-like correlations ...... 15
Applying the AdS/CFT correspondence to non-abelian plasmas ...... 15
PHENIX heavy flavor ...... 15
Quarkonia measurements by the CMS experiment in pp and PbPb collisions ...... 15
Theory ...... 16
Experiments ...... 16
Theory ...... 16
Theory ...... 16
Experiments ...... 16
Correlations and fluctuations from lattice QCD ...... 17 p + A ...... 17
New challenges at the low energy frontier ...... 17 e + A ...... 17
The high energy frontier of A-A ...... 17
Non-conformal holography of light and heavy quark jet quenching at RHIC and LHC . . 17
Jet Modification Via The LPM Effect In Infinite Quark Matter ...... 18
iv Measuring parton energy loss at RHIC ...... 18
Dynamical magnetic effects and the nonphotonic electron puzzle atRHIC ...... 18
Overview of the experimental results by the ALICE Collaboration ...... 19
Results from lead-lead collisions with the ATLAS Detector at the LHC ...... 19
Overview of the experimental results by the CMS Collaboration ...... 19
PHENIX Highlights ...... 20
STAR highlights ...... 20
Opening ...... 20
LHC accelerator ...... 20
Theory overview ...... 20
Heavy-ion collisions and QCD: the big picture ...... 20
Soft physics and hydrodynamics ...... 21
Jets, high-pT hadrons and prompt photons ...... 21
Heavy-quarks and quarkonia ...... 21
Initial conditions, low-x QCD, thermalization ...... 21
QCD phase transition, hydrodynamics, hadronization ...... 21
Jets, high-pT hadrons, and prompt photons ...... 21
Heavy-quarks and quarkonia ...... 21
Medium induced collinear radiation from soft collinear effective theory (SCET) . . . . . 22
Suppression of the repulsive force in nuclear interactions near the chiral phase transition 22
Equation of state of a strongly-interacting QGP and charmonium suppression ...... 23
First-principles derivation of the jet energy-momentum deposition source term in the QGP and its implications for shockwave formation at RHIC and at the LHC ...... 23
Momentum dependence of quarkonium production at RHIC and LHC ...... 24
Strong color fields effects and baryon/meson anomaly in p+p and central Pb+Pb collisions at L H C energies(*)...... 24
An effective theory for jet propagation in dense QCD matter: jet broadening, radiative energy loss and LHC phenomenology ...... 25
Directed Flow in event-by-event hydrodynamics ...... 25
Silicon Tracking for the Compressed Baryonic Matter Experiment at FAIR ...... 26
Directed flow and early thermalization ...... 27
v What is the surface tension of quark gluon bags? ...... 27
DENSE COLD MATTER STUDY WITH SPECIAL TRIGGER AT TWA, NUCLOTRON, NICA AND FAIR. Project Status...... 28
Enhancement of flow anisotropies due to magnetic field in relativistic heavy-ion collisions ...... 28
Initial state fluctuations at RHIC and LHC: hadronic or partonic origin? ...... 28
Centrality dependence of observables in the core - corona model ...... 29
The realistic QCD equation of state in relativistic heavy-ion collisions and the earlyUni- verse ...... 30
Role of Finite Size Baryons in QCD Phase Transition and Critical Point ...... 30
Far-from-equilibrium anisotropic collective flow ...... 31
Describing sQGP through the Friedberg-Lee model ...... 31
Measurements of Jets and Jet Quenching in sqrt(s_NN)=2.76 TeV PbPb Collisions with the ATLAS Detector at the LHC ...... 32
Measurement of elliptic flow in sqrt(s_NN)=2.76 TeV PbPb collisions with the ATLAS de- tector at the LHC...... 32
Measurement of charged particle pseudorapidity density in PbPb collisions at sqrt(s_NN) = 2.76 TeV with the ATLAS detector at the LHC ...... 32
Measurements of charged particle spectra in sqrt(s_NN)=2.76 PbPb collisions with the AT- LAS detector at the LHC ...... 33
Study of Ultraperipheral processes in sqrt(s_NN)=2.76 Pb+Pb collisions with the ATLAS detector at the LHC ...... 33
Measurement of higher-order flow harmonics in sqrt(s_NN)=2.76 TeV Pb+Pb collisions with the ATLAS detector at the LHC ...... 34
Measurements of Jet Production and Jet Fragmentation in sqrt(s_NN) = 2.76 TeV Pb+Pb Collisions with the ATLAS detector at the LHC ...... 34
Jet quenching from RHIC to LHC ...... 34
Effects of parton radiative processes on Quark-Gluon Plasma thermalization ...... 35
Some new results on high-energy ”jet stopping” in AdS/CFT ...... 36
Running coupling corrections to high energy inclusive gluon production ...... 36
Characterizing quark gluon plasma by Heavy Flavors ...... 36
Heavy quarkonia in a quark-gluon plasma: coupled evolution and dynamics ...... 37
Study of the expansion and the phase transition of a quark plasma to an hadron phase with the NJL model using a new QMD approach...... 37
vi QCD thermodynamics at intermediate coupling ...... 38
Moments of charge fluctuations, pseudo-critical temperatures and freeze-out in heavy ion collisions ...... 38
Photon and dilepton production from viscous QGP ...... 39
Hydrodynamical analysis of centrality dependence of charged particle’s multiplicity in √sNN=2.76 TeV Pb+Pb collision ...... 40
Entanglement between deconfinement transition and chiral symmetry restoration . . . . 40
Probing nuclear parton densities and parton energy loss processes through photon + heavy- quark jet production in p-A and A-A collisions ...... 41
Exotic Matter-Antimatter Molecules ...... 41
Energy Dependence of the Identified Hadron Elliptic Flow and QCD Phase Structure . . 42
Quarkonium production at the LHC: QCD corrections and new observables ...... 43
Jets, mach cone, hot spots, ridges, harmonic flow, dihadron and γ-hadron correlations in high-energy heavy-ion collisions ...... 43
Kadanoff-Baym Approach to Thermalization of Gluonic Matter ...... 43
Charged-hadron pseudorapidity distributions in the RDM at LHC energies ...... 44
Suppression of high p_T hadrons in PbPb Collisions at LHC ...... 44
A few new experimental results on particle correlations ...... 45
V1 flow componet at LHC ...... 45
Can we see from jet quenching that quark-gluon plasma becomes more perturbative at LHC than at RHIC ...... 46
Dilepton interferometry: a tool to characterize different phases of matter produced in heavyion collisions ...... 46
Charged Particle’s elliptic flow in 2+1D viscous hydrodynamics at LHC (√s=2.76 TeV)En- ergy in Pb+Pb collision. and QGP viscosity ...... 47
Enhancement of thermal photon production in event-by-event hydrodynamics ...... 47
Initial conditions - Theory perspectives ...... 48
Initial state fluctuations and their effect on the flow ...... 48
Pion quenching and tomography from RHIC to LHC in the WHDG model ...... 49
High resolution numerical scheme for hydrodynamic analysis of heavy ion collisions and formation of an incoming shock wave induced by reheating ...... 49
Bulk viscosity of a pion gas and energy-momentum correlations ...... 50
ATLAS flow ...... 50
vii Collective flow measurements from the PHENIX Experiment ...... 50
Common discussion with 4 experimental speakers ...... 51
Nuclear modification factors from the CMS experiment ...... 51
Recent R_{AA} Results from the PHENIX Experiment ...... 51
Common discussion with 4 speakers ...... 51
Jet measurements by the CMS experiment in pp and PbPb collisions ...... 51
ATLAS jet measurements ...... 52
Common discussion with 4 speakers ...... 52
Heavy-flavor production in PbPb collisions at the LHC measured with the ALICE detector 52
Common discussion with 3 speakers ...... 53
Quarkonium measurements at the LHC with the ALICE detector ...... 53
Common discussion with 2 speakers ...... 53
Hadrochemistry – theory status ...... 54
ALICE hadrochemistry ...... 54 common discussion with 2 speakers ...... 54
STAR: results from the beam energy scan program ...... 54
NA49/NA61: SPS results on fluctuations & correlations ...... 54
Production of identified particles in pp and PbPb collisions at LHC energies with the ALICE detector ...... 54
Correlations and fluctuations measured by the CMS experiment in pp and PbPb collisions 55
The low energy frontier of A-A ...... 55
Physics opportunities of future p-A runs ...... 55
Physics opportunities of e-A colliders ...... 55
Physics opportunities of e-A colliders ...... 55
The high energy frontier of A-A ...... 56 eA collisions at the Large Hadron-electron Collider ...... 56
Hadrochemistry – theory status ...... 56
ALICE hadrochemistry ...... 56 common discussion with 2 speakers ...... 56
Quark production far from equilibrium ...... 56
viii The Very High Momentum Particle Identification Detector atALICE ...... 57
Highly-anisotropic and strongly-dissipative hydrodynamics for early stages of relativistic heavy-ion collisions...... 57
Fireball fragmentation and rapidity correlations of protons ...... 58
Deconfinement and chiral transition in QCD at finite temperature ...... 59
Jet properties in {\it p+p} and their possible modification in cold nuclear matter inSTAR 59
Cavitation and Thermal Dilepton Production in QGP ...... 59
D+ →K- π+ π+ Production in pp collisions at LHC with the ALICE detector ...... 60
First results from hybrid HKM for top RHIC and LHC energies ...... 60
− Non√ Photonic Electron and Charged Hadron Azimuthal Correlation in p+p Collisions at s = 500 GeV in STAR ...... 61 √ Dielectron production in Au+Au collisions at sNN = 39 GeV at STAR ...... 62
QGP viscosity coefficients: from weak to strong coupling ...... 62
Equation of state of strongly interacting matter: spectra for thermal particles and intensity correlation of thermal photons ...... 63
Interference of thermal photons from quark and hadronic phases in relativistic collisions of heavy nuclei ...... 63
Two freeze-out analysis of hadron yields and spectra at RHIC ...... 64
Measurements of Non-photonic Electron Spectra and Elliptic Flow in Au+Au Collisions from STAR at RHIC ...... 64
Effects of final state interactions on charge separation in relativistic heavy ion collisions 65
Nucleon mass generated from confinement and a dynamic generation of the quark masses ...... 65
Beauty in the QGP from the lattice ...... 65
Dimuon radiation at the CERN SPS within a hybrid evolution model ...... 66
D+ analysis in Pb-Pb collisions at √ sN N = 2.76 TeV at the LHC with ALICE...... 66
Next-to-leading order analysis of inclusive jet, tagged jet and di-jet production in PbPb collisions at the LHC ...... 67
Reconstruction of Ds mesons in the ALICE Experiment at LHC ...... 67
Dissipative dynamics of highly anisotropic plasmas ...... 68 √ Event anisotropy v2 of identified hadrons and light nuclei in Au+Au collisions at sNN = 7.7, 11.5 and 39 GeV with STAR ...... 68 √ Centrality dependence of the Υ Nuclear Modification Factor at sNN = 200 GeV measured with STAR ...... 69
ix Investigating jet and non-jet contributions to long range pseudo-rapidity correlations in di-hadron measurements from STAR...... 69
Leading hadron PID effects in di-hadron angular correlations in STAR ...... 70
Charge fluctuations in chiral models and the QCD phase transition ...... 71
Roles of Axial Anomaly on Neutral Strongly Interacting Matter —- New Critical Points at Low Temperature and the Absence of Chromomagnetic Instabilty —- ...... 71
J/psi analysis in proton+proton at 7 TeV in the ALICE muon spectrometer using a pT - y correction method...... 72
Search for the QCD Critical Point: Higher Moments of Net-proton, Net-charge Multiplicity Distributions from the RHIC Beam Energy Scan ...... 72
Multihadron production in hadronic and nuclear collisions ...... 73
Prospects for charm RAA in PbPb collisions at LHC via D0->Kpi reconstruction in ALICE 73
STAR science for the coming decade ...... 74
Development of the CBM RICH detector ...... 74
Dynamical equilibration of strongly-interacting ’infinite’ parton matter within a Parton- Hadron-String Dynamics (PHSD) transport approach ...... 75
Jets in QCD media: from color coherence to decoherence ...... 75
Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC ...... 76
Dissipative hydrodynamics for relativistic multi-component systems ...... 77
Linear confinement and phase transitions in holographic QCD ...... 77
From RHIC to LHC: heavy quarks and J/psi in a partonic transport model ...... 77
Percolation√ of Color Sources and the Equation of State of QGP in central Au-Au collisions at sNN =200 GeV ...... 78 √ Open charm hadron measurement in pp and Au+Au collisions at s = 200 GeV in STAR 78
A High Level Online Tracking Trigger for the STAR experiment at RHIC ...... 79
Relativistic fluid dynamics from the Boltzmann equation: going beyond the 14-moment approximation ...... 80
Determination of relaxation times at weak and strong coupling ...... 80 √ Dielectron Continuum Production from sNN = 200 GeV pp and Au+Au collisions at STAR ...... 81
Observation of the antimatter helium-4 nucleus ...... 82
Commissioning and detector performance of the VTX-Pixel detector for RHIC-PHENIX experiment...... 82
x STAR measurements of bottom to charm ratio and heavy quark interaction with theQCD medium through non-photonic electron-hadron correlations ...... 82 √ Inclusive charged hadron elliptic flow in Au + Au collisions at sNN = 7.7, 11.5 and 39 GeV ...... 83
Probing the gluonic structure of matter at a future Electron-Ion Collider ...... 83 √ Directed flow of Identified Particles in Au+Au Collisions at sNN = 39, 11.5 and 7.7 GeV from the STAR Experiment ...... 84
Charge-to-Neutral fluctuation in AuAu collisions at Forward rapidity atRHIC...... 84
Viscous hydrodynamic evolution with non-boost invariant flow for the color glass conden- sate ...... 85
Hydrokinetic predictions for femtoscopy scales in A+A collisions in the light of recent ALICE LHC results ...... 86
Mach Cones and Two-Particle Correlations: The Origins in a Kinetic Transport Approach 86
Shear Viscosity of the QGP in Central A-A Collisions at RHIC and LHC Energies in the Color String Percolation Approach ...... 87
Finite lifetime effects on the photon production from a quark-gluon plasma ...... 87 √ Elliptic Flow of charged particles in Au+Au collisions at sNN = 7.7, 11.5 and 39 GeV from STAR ...... 88
Low-mass√ meson production through di-leptonic decays in p+p and Au+Au collisions at sNN = 200 GeV from STAR ...... 88
Chirality, magnetic field and parity violation in hot QCD matter ...... 88
Leptonic decay of phi(1020) meson measured with the STAR experiment ...... 89
Finite-size scaling search for the critical endpoint of QCD in heavy ion data ...... 89
Identified hadron production from the RHIC beam energy scan program in the STARex- periment ...... 90
Multiparticle system in high energy hadronic/nuclear collision and matter state of early universe ...... 90
Viscous relaxation time in relativistic hydrodynamics ...... 91
Energy dependence of the freeze out eccentricity from azimuthal dependence of HBT at STAR ...... 91
D0 meson production in pp collisions at the LHC with ALICE and prospects for charm flow measurements in PbPb collisions ...... 91
Phenomenological interpolation of inclusive J/psi production to proton-proton collisions at sqrt(s)=2.76 TeV and 5.5 TeV ...... 92
Direct photons at low transverse momentum – a QGP signal in pp collisions at LHC . . 92
xi Exploring compressed nuclear matter with HADES ...... 93
Dynamics near QCD critical point by dynamic renormalization group ...... 94
QCD Phase Diagram based on Strong Coupling Lattice QCD ...... 94
Sensitivity of the elliptic flow coefficient to a temperature-dependent shear viscosity-to- entropy density ratio in ultrarelativistic heavy-ion collisions at RHIC and LHC . . . 95
Chiral transition in a magnetic field and at finite baryon density ...... 95
Suppression of large transverse momentum hadrons in central Pb+Pb collision at LHC . 96
Turbulent fluctuations around Bjorken flow ...... 96
Medium-induced modifications of color flow in high transverse momentum processes . . 97
Probing deconfinement with chiral effective models at imaginary chemical potential . . 97
Charmonium mass in hot and dense hadronic matter from QCD sum rules ...... 98
Determining initial state fluctuations from flow measurements ...... 98
Understanding initial state fluctuations ...... 99
Ratio of J/Psi to Rho Photoproduction Cross Sections at the Relativistic Heavy Ion Collider with STAR ...... 99
Jet-Hadron Correlations in STAR ...... 100
Bulk viscosity in heavy-ion collision ...... 100
Lattice QCD based equation of state at finite baryon density ...... 100
D0 production in p+p sqrts = 200 GeV collisions at STAR ...... 101
Transition temperature and the equation of state from lattice QCD, Wuppertal-Budapest results ...... 101
Forward-Backward Multiplicity Correlations for Identified Particles at STAR ...... 102
Elliptic and triangular flow in the event-by-event 3+1D viscous hydrodynamics . . . . . 103
Spectrum of initial fluctuations in the little bang ...... 103
The STAR Upgrade Program ...... 104
Local baryon-strangeness correlation from hypernuclei and coalescence volume from light nuclei in relativistic heavy ion collisions ...... 104
Spectrum of fermion coupled with massive vector boson at finite temperature in gauge invariant formalism ...... 105
Centrality dependence of viscous quark gluon plasma at LHC ...... 105 √ Dynamical K/π, p/π, and K/p fluctuations in sNN = 7.7-200 GeV Au+Au collisions . 106
Correlations and fluctuations from lattice QCD ...... 107
xii J/Psi production in proton-proton collisions at sqrt(s) = 2.76 TeV in the ALICE Forward Muon Spectrometer ...... 107
Inhomogeneous phase during the chiral transition ...... 107
Spectra, flow and HBT in PbPb collisons at the LHC ...... 108
Jet quenching and elliptic flow in heavy ion collisions at RHIC and LHC within apQCD- based partonic transport model ...... 109
Charge balance correlations and contributions to local parity violation observables . . . 109
Mix-ratios of Higher Order Moments of Proton and Kaon as a baseline of QCD Critical Point search at RHIC ...... 110
Centrality dependence of muon tracking efficiency in the ALICE Forward Muon Spectrom- eter for Pb-Pb collisions at 2.76 TeV...... 110
Event-by-event hydrodynamics and elliptic flow from fluctuating initial state ...... 110
Strongly intensive measures for chemical fluctuations in A+A and p+p collisions: statistical and transport models...... 111
AAMQS: a non-linear QCD description of new HERA data at small-x ...... 111
Heavy quarkonium measurements from PHENIX ...... 112
Jet modification from RHIC to LHC ...... 112
Polarization Effects at RHIC and LHC ...... 113
Jet Quenching via Jet Collimation ...... 113
Can transport peak explain the low-mass enhancement of dileptons at RHIC? ...... 114
Higher moments of Net Kaon Fluctuation in the Beam Energy Scan of STAR ...... 114
QCD thermodynamics by numerical simulations of Lattice QCD with Wilson-type quarks 115
Signals from the QCD phase transition in the early universe ...... 115
Heavy ion program at JINR NICA/MPD facility ...... 116
J/Psi production and correlation in p+p and R_{AA} at high-pt in Au+Au collisions . . . 116
Hadron Productions at LHC Energies with HIJING2.0 Model ...... 117
Measurement of J/ψ photoproduction in ultra-peripheral Au+Au collisions at √sNN=200GeV using the PHENIX detector ...... 117
Search for local strong parity violation in STAR using multiple observables ...... 118
Vorticity and Chaos in Heavy Ion Collisions ...... 118
Topological interactions of non-Abelian vortices with quasi-particles in high density QCD ...... 118 √ J/ψ polarization in p+p collisions at s = 200 GeV at STAR ...... 119
xiii Relativistic theory of hydrodynamic fluctuations ...... 119
Study of Λ−Λ correlations and search for the H-dibaryon with the STAR detector at RHIC ...... 119
Continuous Time Monte Carlo for QCD in the Strong Coupling Limit ...... 120
Radiative energy loss reduction in a plasma due to damping ...... 120
Heavy quark diffusion from lattice QCD spectral functions ...... 121
Examining real-time functions on the lattice using inverse propagator and self-energy . 121
Local Parity Violation or Local Charge Conservation/Flow? A Reaction-Plane-Dependent Balance Function Study ...... 122
Eccentricity and elliptic flow in proton-proton collisions from parton evolution . . . . . 122
Light meson production in d+Au collisions measured by PHENIX experiment at sqrt(s_NN) = 200 GeV ...... 123
Feasability study for a Muon Forward Tracker in ALICE ...... 123
Quark recombination and heavy quark diffusion in hot nuclear matter ...... 124
Dragging D mesons by hot hadrons ...... 124
Towards the realization of the CBM-Micro Vertex Detector: Technological challenges and detector response simulation ...... 125
Scale for the phase diagram of quantum chromodynamics ...... 125
Understanding the equilibration of matter from time-dependent correlator ...... 125
0 Methods for extracting elliptic flow (v2) and cocktail fits of ρ vector-meson in STAR at RHIC ...... 126
Charged Particle Ratios for p+p Collisions in √s = 62.4 GeV at RHIC ...... 126
The thermal model on the verge of the ultimate test: the LHCdata ...... 127 √ D meson reference spectra in pp collisions at s = 2.76~TeV with ALICE ...... 128
Search for the QCD critical point by higher moments of the net-charge multiplicity distri- bution ...... 128
Interference effects in medium–induced gluon radiation ...... 129
Ultrasoft Fermionic Mode in QED and QCD plasmas ...... 129
Measurement of J/Ψ elliptic flow in Au+Au collisions at √sNN=200 GeV in STAR experiment ...... 130
Measurement of light vector mesons by PHENIX experiment at RHIC ...... 130
Charmonium production on fixed target with proton and lead beams ofLHC ...... 131
xiv Completion of mass production of silicon pixel ladders for PHENIX silicon vertex tracker (VTX) ...... 132 √ Underlying event studies in d+Au collisions at sN N=200 GeV from STAR ...... 132
Fluctuations and the Ridge from RHIC to LHC ...... 133
Measurement of Baryonic Resonances in pp Collisions at the LHC with ALICE ...... 133
Direct photon production in heavy ion collisions in PHENIX experiment at RHIC . . . . 134
J/\psi production at mid-rapidity in pp collisions at \sqrt{s}=7 TeV, measured with ALICE 134
QCD critical point and event-by-event fluctuations ...... 135
Measurement of dNch/deta with the ALICE VZERO detector in central Pb-Pb collisions at 2.76 TeV ...... 135
Reconstruction and first observation of the charmed baryon Λc in pp collisions at√s=7 TeV with ALICE ...... 135
Equilibration in classical Yang-Mills dynamics ...... 136
Critical behavior of Binder-like ratios and ratios of higher cumulants of conserved charges in QCD deconfinement phase transition ...... 136
Identifying multi-quark hadrons from heavy ion collisions ...... 137
Extended Schematic Model for Hadrons, and What Happens to the Radius of an Excited Hadron ...... 138
Fluctuation, dissipation, and thermalization in non-equilibrium AdS5 black hole geome- tries ...... 138
A Forward Calorimeter (FoCal) as upgrade for the ALICE Experiment at CERN . . . . . 139
Nonperturbative Particle Production in Boost-Invariantly Expanding Electric Fields and Two-Particle Correlations ...... 139
Contribution from hard partons to the bulk elliptic flow ...... 140
The ALICE Inner Tracking System: performance with proton and lead beams ...... 140
Hunting electrons from heavy-flavour hadron decays with the ALICE Transition Radiation Detector in proton-proton collisions at √s = 7 TeV ...... 141
Nuclear suppression at non-zero baryonic chemical potential ...... 141
New results on event-by-event ratio fluctuations in PbPb collisions at CERN SPS energies 142
Jet studies in 200 GeV d+Au collisions from the STAR experiment at RHIC ...... 142 √ Charged particle production with respect to the Reaction Plane in Pb-Pb collisions at sN N= 2.76 TeV ...... 143
Dilepton production in heavy-ion collisions within the parton hadron string dynamics (PHSD) transport approach ...... 143
xv Deconfinement and chiral symmetry in effective models with fermions in higher represen- tations ...... 144
Flow analysis with event-plane method using the VZERO detector in Pb-Pb collisions at sqrt(sNN)=2.76 TeV collected by the ALICE experiment at the LHC ...... 144
Pion production in p+p and p+C interactions at 31 GeV/c ...... 145
Distortion of photon HBT image by the vacuum birefringence in strong magnetic field . 145
Identified particle v3 measurements at 200GeV Au+Au collisions at RHIC-PHENIX experi- ment ...... 146
Upgrade of ALICE Electromagnetic Calorimeter to enhance di-jet measurements . . . . 146
Pseudorapidity dependence of charged hadron multiplicity and transverse energy densities in PbPb collisions from CMS ...... 147
Charged hadron azimuthal anisotropy (v_2) in sqrtsNN = 2.76 TeV PbPb collisions from CMS ...... 147
Weak boson production measured in PbPb and pp by CMS ...... 148
Centrality and transverse momentum dependence of the nuclear modification of charged particle spectra in PbPb collisions at 2.76 TeV from CMS ...... 148
Measurement of inclusive isolated photons in PbPb collisions with CMS ...... 149
Rapidity and centrality dependence of transverse energy distributions in PbPb collisions from CMS ...... 149
Study of jet quenching using dijets in PbPb Collisions with CMS ...... 150
Dijet fragmentation functions measured in PbPb collisions with CMS ...... 150
The dynamics of quark droplets ...... 151
Monte-Carlo simulation for elastic energy loss of high-energy partons in a hydrodynamical background ...... 151
Jet reconstruction with particle flow in heavy-ion collisions with CMS ...... 151
Charmonium production measured in PbPb and pp collisions by CMS ...... 152
Bottomonium production measured in PbPb and pp collisions byCMS ...... 152
Observation of a ridge correlation structure in high multiplicity pp collisions with CMS . 153 √ Dihadron correlations in PbPb collisions at sNN = 2.76 TeV with CMS ...... 153 √ Measurement of higher order flow harmonics in PbPb collisions at sNN = 2.76 TeV by CMS ...... 154
Electron reconstruction and Z measurement in the di-electron channel in PbPb collisions with CMS ...... 154
xvi √ Study of beauty production in pp collisions at s = 7 TeV with ALICE, using displaced electrons ...... 154
Readout of the CMS experiment during the 2010 heavy ion run ...... 155
Performance of the CMS Zero Degree Calorimeter for PbPb and pp running ...... 155
B → J/ψ measurement in PbPb at √s_NN = 2.76 TeV using CMS ...... 156
Data-driven efficiencies for di-muon measurements in heavy ion collisions withCMS . . 156
Effect of the polarization on the acceptance for quarkonia studies in PbPb at √sNN=2.76 TeV in CMS ...... 156
Performance of PHENIX HBD in Au + Au central collisions ...... 157
Quarkonia propagation and collectivity in the QGP: Towards the suppression of quarkonia suppression ...... 157
ALICE detector upgrades ...... 158
Large-N_c behavior of hadronic models at nonzero temperature ...... 158
Construction and Installation of the PHENIX silicon pixel vertex tracker ...... 159 √ Forward and Backward to Mid-Rapidity Correlations Measured in d+Au Collsions at SNN = 200 GeV with the PHENIX Detector ...... 159
Particle identification in the ALICE experiment ...... 160
U(1)A anomaly effects on phase diagrams in chiral random matrix model ...... 160
The Level-0 trigger of the ALICE Electromagnetic Calorimeter ...... 161
Charmonium spectral functions at finite momenta in the quark-gluon plasma from lattice QCD ...... 161
Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions atLHC . . . . . 162
Influence of tubular initial conditions on two-particle correlations ...... 162
Using separated bottom and charm contribution to pin down the role of radiative energy loss for heavy quarks ...... 163
Particle multiplicities in high-energy hadronic collisions at RHIC/LHC from CGC with local rcBK evolution ...... 164
Global characteristics, long-range correlations, ridge and femptoscopic radii in pp-collisions at LHC ...... 164 √ Dimuon pairs from In-In collision at sNN = 17.3 GeV at SPS energies ...... 165
Nuclear suppression at large pT and xF: Direct photons from RHIC to LHC ...... 165
Measurement of neutral mesons at ALICE by means of one photon detected in electromag- netic calorimeter and another from its conversion in central tracking system . . . . . 166
xvii Low pT direct photon production in 200GeV d+Au collisions measured by the PHENIX detector ...... 166
Studies for an upgrade of the ALICE Inner Tracking System ...... 167
Feasibility study of muon chamber for CBM experiment at FAIR ...... 168
D meson production cross sections in pp collisions at √s = 7 TeV, measured with the ALICE detector ...... 168
Lattice study of the second order transport coefficients ...... 169
Study of pion-pion correlations at LHC and RHIC energies in pp collisions within the quark- gluon string model ...... 169
A comprehensive study of the high-pt particle correlations in pp collisions at LHC/ALICE 169
Charmonium and open-charm production in p-A collisions at the SPS ...... 170
Measurement of Low Mass Electron-Positron Pairs with ALICE ...... 170
Dissipative effect on the thermal photon spectra ...... 171
Femtoscopy of the proton-proton collisions at the LHC with pion-pion Bose-Einstein cor- relations in ALICE ...... 171
Resonance measurement in pp and PbPb collisions at LHC with the ALICE detector . . . 172
K0sK0s correlations in 7 TeV proton+proton collisions from the ALICE experiment at the LHC ...... 172
Jet Reconstruction and Jet Background Classification with the ALICE experiment in PbPb collisions at the LHC ...... 173 √ Nuclear modification of charm quarks in Pb-Pb collisions at sNN =2.76 TeV at LHC . . 173
K0s and Lambda production in PbPb collisions with the ALICE experiment ...... 174
Unintegrated gluon distributions and k_t-factorization in forward hadron production in DIS and pA collisions ...... 174
Multi-strange particle measurements in 7 TeV proton-proton and 2.76 TeV PbPb collisions with the ALICE experiment at the LHC ...... 175
The next decade of physics with PHENIX ...... 175 √ Elliptic flow at high transverse momentum in PbPb collisions at sNN = 2.76~TeV with the ALICE experiment ...... 175
Pt spectra of hadrons identified with the ALICE Inner Tracking System ...... 176
Measurement of J/psi production at forward rapidity in pp collisions at sqrt(s)= 2.76 and 7 TeV with ALICE ...... 176
Electrical conductivity and thermal dilepton rate from quenched lattice QCD...... 177
xviii √ Measurement√ of π/K/p spectra with ALICE in proton-proton collisions at s = 900 GeV and s = 7 TeV ...... 177
Photons at RHIC and at the LHC: the role of viscosity and of event-by-event fluctuations 177
Anisotropic flow of charged particles at 2.76 TeV measured with the ALICE detector . . 178
Measurements of low mass dielectrons in Au+Au collisions with the HBD upgrade of the PHENIX detector ...... 178
Heavy-flavor production cross section in the semi-electronic channel at mid-rapidity inpp collisions at sqrt(s)=7 TeV with ALICE ...... 179 √ Collision energy dependence of the flow and spectra results in Au+Au collisions at sNN = 7.7-200 GeV from PHENIX ...... 179
New experiments for study of in-medium vector mesons at J-PARC ...... 180
Energy dependence of energy loss in Au+Au collisions at PHENIX ...... 180
Pseudorapidity√ density of charged particles and its centrality dependence in Pb-Pb colli- sions at sNN = 2.76 TeV ...... 181
System-size dependence of particle ratio fluctuations in Pb+Pb collisions at 158 AGeV . . 181
LHC results on femtoscopic pi+pi correlations from the UrQMD transport approach . . . 182
Validity of the hadronic freeze-out curve ...... 182
Derivation of Causal Relativistic Hydrodynamic Equations and Novel Moment Method . 183
Recent PHENIX results on open heavy flavor ...... 184
Triangular flow and nonflow by 2-, 4-, and 6-particle cumulants fromSTAR ...... 184
Midrapidity charged particle directed flow in PbPb collisions at sqrt{s_{NN}} = 2.76 TeV measured with ALICE at the LHC ...... 185
Photonuclear interactions in ultra-peripheral Pb+Pb collisions at the LHC ...... 185
Event-by-event mean pT fluctuations in pp and PbPb collisions measured by the ALICE experiment at the LHC ...... 186
Shear viscosity in a partonic cascade ...... 186
My suppression, your flow, his Cronin - our insight ...... 186 √ PHENIX measurements of higher-order flow harmonics in Au+Au collisions at sNN = 200 GeV: implications for Initial-eccentricity models and the specific viscosity of the Quark Gluon Plasma ...... 187
Charged-particle transverse momentum spectra in proton-proton collisions at √s = 0.9 TeV, 2.76 TeV and 7 TeV measured with ALICE at the LHC ...... 187
Electromagnetic superconductivity of vacuum in strong magnetic field and heavy ion col- lisions ...... 188
xix Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decays at Mid-Rapidity in Pb-Pb Collisions at sqrt(s_NN)=2.76 TeV with ALICE ...... 188
Charmonium dynamics in the UrQMD transport model ...... 188
Net-baryon-, net-proton-, and net-charged particle kurtosis in heavy-ion collisions within a relativistic transport approach ...... 189
Photoproduction of Vector Mesons in Ultra-Peripheral Pb-Pb Collisions at the LHC . . . 189
Measurement of J/ψ → e+e− Production in Pb-Pb Collisions at √s = 2.76 TeV with ALICE at the LHC ...... 190
J/psi production at forward rapidity in PbPb collisions at sqrt(s_NN) = 2.76 TeV, measured with the ALICE detector ...... 190 √ Low mass dimuon production in proton-nucleus collisions at s = 27.5~GeV with the NA60 experiment ...... 191
Study of central production in pp-collisions at √s=7 TeV with the ALICE experiment . . 191
Production of neutral pions and eta-mesons in pp collisions measured with ALICE . . . 192
Measurement of the Multiplicity Dependence of J/ψ → e+e− Production in √s = 7 TeV pp Collisions with ALICE at the LHC ...... 192 √ Charge dependent azimuthal correlations in PbPb collisions at sNN = 2.76~TeV . . . . 193
Vector meson production in pp collisions at sqrt(s)=7 TeV, measured with the ALICE detec- tor ...... 193
Constraining Cold Nuclear Matter Effects on J/ψ production in Au +Au Collisions . . . 194
Measurements of Bose-Einstein correlations at LHC with CMS ...... 194
MEASUREMENT OF SINGLE-MUON AND J/\psi PRODUCTION AT FORWARDRAPIDITY AS A FUNCTION OF THE COLLISION MULTIPLICITY IN PP COLLISIONS AT \sqrt{s} = 7 TeV WITH ALICE ...... 194
Suppression of neutral pion production at large√ transverse momentum measured with the ALICE experiment in PbPb collisions at sNN =2.76 TeV ...... 195
Production of nuclei and anti-nuclei in pp and Pb-Pb collisions with ALICE at the LHC . 195
Charged particle production at large transverse momentum in PbPb collisions at sqrt(s)=2.76 TeV measured with ALICE at the LHC...... 196 √ Transverse sphericity in minimum bias proton-proton collisions at s = 0.9 and 7 TeV with ALICE at the LHC ...... 196
Measurement of J/psi polarization at forward rapidity in pp collisions at sqrt(s)=7 TeV with the ALICE detector ...... 197
Topological reconstruction of strange hadrons in Pb-Pb collisions with the ALICE experi- ment ...... 197
xx Inclusive photon production at forward rapidities for pp collisions at √s = 0.9 TeV and 7 TeV in ALICE at the LHC ...... 197
Photoproduction of J/Psi in Ultra-Peripheral Pb+Pb collisions at sqrt(s_NN)=2.76 TeV in ALICE ...... 198
Diffraction dissociation of protons in proton-proton collisions at \sqrt{s} = 0.9 TeV, 2.76 TeV and 7 TeV with ALICE at the LHC ...... 198
Cold Nuclear Modification of J/psi Production in d+A and A+A Collisions ...... 199
Measurement of inclusive neutral pion yields in in p+p and Pb+Pb collisions at √sNN=2.76 TeV with the ALICE EMCal ...... 199
Nonequilibrium effects at the phase transition in chiral fluid dynamics including dissipation and noise ...... 199
High-pT suppression of Lambda and K0s in PbPb collisions at sqrt(sNN) = 2.76 TeV with ALICE ...... 200
Triggered di-hadron correlations in PbPb collisions from the ALICE experiment . . . . . 200
Elliptic Flow from the Parton-Hadron-String-Dynamics ...... 201
Multiplicity Dependent Di-Hadron Correlations Measured with ALICE at the LHC . . . 201
Anomalous baryon production and its interplay with jet energy loss at RHIC and LHC energies ...... 202 √ A data driven validation of the Pythia jet cross section in pp collisions at s = 2.76 TeV 202
Charged KK femtoscopy correlations from 7 TeV pp collisions measured by ALICE collab- oration...... 203
Untriggered di-hadron correlations in PbPb \sqrt{s_{NN}} =2.76 TeV collisions from the AL- ICE experiment ...... 203
Measurement of Upsilon suppression in Au+Au collisions at 200 GeV ...... 204
Evaluation of the identification efficiency of the ALICE HMPID detector in p-p collisions at √s = 7 TeV by means of V0 decays ...... 204
Energy dependence of π0 suppression in Au+Au collisions ...... 204
The influence of bulk evolution models on heavy-quark phenomenology ...... 205
Azimuthal anisotropy of neutral pion production in Pb+Pb collisions at sqrt(s_NN) = 2760 GeV measured by ALICE ...... 205
Modeling heavy ion collisions with CHIMERA ...... 206
Identified particles from viscous hydrodynamics ...... 206
The Rise and Fall of the Ridge at RHIC andtheLHC ...... 207
Three particle correlations as a probe of eccentricity fluctuations ...... 207
xxi Heavy ion initial conditions and correlations between higher moments in the spatial anisotropy ...... 208
Measurement of the electromagnetic dissociation cross-section of Pb nuclei at 2.76 A Tev with the ALICE ZDC ...... 208
Elliptic and triangular flow of identified particles measured with the ALICE detector. . . 209
Jet production measurements with the ALICE Experiment in pp collisions at the LHC . . 209
Measurement of Charge Multiplicity Asymmetry Correlations to Search for Chiral Mag- netic Effect in Heavy Ion Collisions by STAR ...... 209
Ridge Studies in Pb+Pb Collisions at the LHC based on Number and Transverse Momentum Two-Particle Correlation Functions ...... 210
Charge Fluctuations in Pb-Pb Collisions at √sNN = 2.76 TeV measured by ALICE experiment ...... 210
Towards the phase diagram of QCD ...... 211
Femtoscopy of the system shape fluctuations in heavy ion collisions ...... 211
Two-pion Bose-Einstein correlations in PbPb collisions at 2.76 TeV with ALICE . . . . . 212
Probing nuclear matter with jets and γ-hadron correlations: results from PHENIX . . . . 212
Status of the Search for Hadronic Squeezed Correlations at RHIC Energies ...... 212 √ D meson nuclear modification factors in PbPb collisions at sNN = 2.76 TeV, measured with the ALICE detector ...... 213
Transverse momentum distributions of pions, kaons and protons for high multiplicity and close to azimuthal isotropic events in 7 TeV pp collisions with the ALICE experiment at the LHC ...... 214
Rapidity and centrality dependence of identified hadrons in Au+Au and p+p collisions at 200 GeV ...... 214
Development of the FARICH detector as a possible upgrade for ALICE HMPID system . 215
Droplets in the cold and dense chiral phase transition ...... 215
Long-Range (Forward-Backward) Pt and Multiplicity Correlations in pp Collisions at 0.9 and 7 TeV ...... 216
Cold nuclear matter physics at low-x from d+Au collisions at PHENIX ...... 217
Jets and Underlying Events in p+p Collisions at LHC energies ...... 217
Charged-particle multiplicity, centrality and the Glauber model with ALICE at 2.76 ATeV 218
Coulomb effects in relativistic heavy ion collisions from CBM experiment ...... 218
Exact analytic hydrodynamical results and estimations of the initial conditions in p+p and Pb+Pb collisions at LHC ...... 218
xxii Cross section normalization in ALICE ...... 219
Proposal of new super-compact calorimeter design for the forward physics ...... 219
Measurement of electrons from heavy-flavor decays in p-p and Pb-Pb collisions with the ALICE EMCAL ...... 220
Hadron-Resonance Correlation in pp collisions at the LHC with ALICE ...... 220
Di-electron analysis in Au+Au collisions using the PHENIX Hadron Blind Detector . . . 221
Effect of running coupling on photons from jet - plasma interaction in relativistic heavy ion collisions ...... 221
Nuclear modification factor in an anisotropic Quark-Gluon-Plasma ...... 222
Open heavy flavor physics in the muon channel with ALICE in pp collisions at7TeVand PbPb at 2.76 TeV ...... 222
Underlying Event measurement in pp collisions with the ALICE experiment at LHC . . . 223
Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV, 2.76 TeV and 7 TeV, with ALICE at LHC ...... 223
Initial condition fluctuations in heavy ion collisions ...... 224
Detector effects and systematic uncertainties in the directed flow measurement withspec- tator neutrons in ALICE at LHC...... 224
The ALICE EMCal Overview and Status ...... 224
Characterizing cold nuclear matter effects through dielectrons in d+Au collisions at√NN = 200 GeV at PHENIX ...... 225
Projectile Spectator Detector for the heavy ion program of the NA61/SHINE experiment at the CERN SPS ...... 225
Identified particle flow methods in ALICE at the LHC ...... 226
A Design for a Novel TOF Detector with 10 picosecond Resolution ...... 226
Propose of studying the symmetry energy of asymmetric nuclear matter under super-saturation density at the Cooling Storage Ring at Lanzhou ...... 226
Azimuthal correlation between photon/π0 and charged hadrons with the ALICE experi- ment ...... 227
Neutral Pion production in PbPb collisions at sqrt(s_NN)=2.76 TeV measured by ALICE via photon conversions ...... 227
Measurement of pi0 production in p+p collisions at sqrt( s ) = 7 TeV with the ALICE EMCal ...... 228
Studies of ω(782) → π0γ → 3γ in p+p collisions at √s = 7 TeV with the ALICE electromag- netic calorimeters ...... 228
xxiii Measurement of eta meson production in pp collisions at √s = 7 TeV with the ALICE elec- tromagnetic calorimeter ...... 229 pi0 and eta meson production in pp collisions at 0.9, 2.76 and 7 TeV measured with ALICE PHOS ...... 229
Correlation Between Mean pT and Charged Particle Multiplicity in pp Collisions at √s = 0.9, 2.76 and 7 TeV with ALICE ...... 229
Energy density in Pb-Pb Collisions at LHC ...... 230
Transverse energy measurements with ALICE in pp and Pb-Pb collisions ...... 230
Ridge Studies in Pb-Pb Collisions at the LHC based on Number and Transverse Momentum Two-Particle Correlation Functions ...... 231
Three-Particle Jet-Like Correlations in Pb-Pb Collsions at sqrt(s_{NN})=2.76 TeV atALICE 231
Prompt and detached J/psi production in p–p collisions at Sqrt(s) = 7 TeV with the ALICE detector ...... 232
Production of Neutral Mesons Identified by ALICE-PHOS in Pb-Pb collisions at sqrt{s_{NN}}=2.76TeV ...... 232
R&D on MRPC for STAR MTD ...... 232
Femtoscopy of PbPb and pp collisions at the LHC with the ALICE experiment ...... 233
Flow - Theory perspective ...... 233
Common discussion with 4 speakers ...... 234
Fluctuations & correlations – TH perspective ...... 234
Results from correlation studies in ALICE ...... 234
Jet yield enhancement in high-tower trigger events with the ALICE Electromagnetic Calorime- ter ...... 234
STAR correlations and fluctuations ...... 234
Common discussion with 4 speakers ...... 235
Presentation of QM12 ...... 235
Closing ...... 235
ALICE vertexing performance and charm reconstruction ...... 235
Preparation for open charm elliptic flow measurement via D-meson decay to hadrons with ALICE ...... 235
Probing the gluonic structure of matter at a future Electron-Ion Collider ...... 236 eA collisions at the Large Hadron-electron Collider ...... 236
Proposal for QM13/14 in Japan ...... 236
xxiv Preparation of QM2012 at Washington ...... 237
Proposal for QM13/14 in Darmstadt ...... 237
Leptonic observables in sqrt(s_NN)=2.76 TeV PbPb collisions measured with the ATLAS detector at the LHC ...... 237
Proposal for QM13/14 in Bologna ...... 237
Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV and 7 TeV, with the ALICE Forward Multiplicity Detector at LHC ...... 237
Charged pion spectra at high pT measured via dE/dx with the ALICE TPC ...... 238
Charged pion spectra at high pT measured via dE/dx with the ALICE TPC ...... 238
Proposal for a QM in Brazil ...... 238
QM2011 ...... 239
First B→J/ψ measurement in PbPb collisions at 2.76 TeV with the CMS detector . . . . . 239
First measurement of Upsilon suppression ...... 239 pending ...... 239
Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decays at Mid-Rapidity in Pb-Pb Collisions at 2.76 TeV with ALICE ...... 239
Probing nuclear parton densities and parton energy loss processes through photon + heavy- quark jet production in p-A and A-A collisions ...... 239
Dimuon radiation at the CERN SPS within a hybrid evolution model ...... 239
Local Parity Violation or Local Charge Conservation/Flow? ...... 240
Production of (anti)nuclei in pp and PbPb collisions with ALICE at the LHC ...... 240
Continuous Time Monte Carlo for QCD in the Strong Coupling Limit ...... 240
xxv xxvi QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
1 / 34
Tagging of eta decay products in Bose-Einstein correlations to an- alyze chiral restoration
Máté Csanád1
Mónika Kőfaragó 1
1 Eötvös University
In case of chiral U_A(1) symmetry restoration the mass of the eta’ boson (the ninth, would-be Gold- stone boson) is decreased, thus its production cross section is heavily enhanced. The eta’ decays (through one of its decay channels) into five pions. These pions will not be correlated intermsof Bose-Einsten correlations, thus the production enhancement changes the strength of two-pion corre- lation functions at low momentum. Preliminary results strongly support the mass decrease of the eta’ boson. In this paper we propose a method to select pions coming from eta’ decays. We investigate the efficiency of the proposed kinematical cut in several collision systems and energies with several simulators. We prove that our method can be used in all investigeted collision systems.
2 / 35 Equation of state and initial temperature of quark gluon plasma at RHIC
Mate Csanad1
Imre Májer 1
1 Eötvös University
In gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) a perfect fluid of quarks, some- times called the strongly interacting quark gluon plasma (sQGP) is created for an extremely short time. The time evolution of this fluid can be described by hydrodynamical models. After expansion and cooling, the freeze-out happens and hadrons are created. Their distribution reveals information about the final state of the fluid. To investigate the time evolution one needs to analyze penetrat- ing probes, such as direct photon spectra. Distributions of low momentum photons was published in 2010 by PHENIX. Such low momentum distributions can be compared to hydrodynamics to de- termine the equation of state and the initial temperature of sQGP. In this paper we analyze a 3+1 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution of low momentum thermal photons and other observables from the model. Using earlier fits of this model to hadronic spectra, we compare photon calculations to measurements from RHIC. We find that the initial temperature of the center of the fireball is at least 519+-12 MeV, while for a time averaged equation of state we get c_s=0.36+-0.02. We also find an interesting shape of direct photon elliptic flow.
131 / 37 The phase diagram in T-mu-Nc space
Giorgio Torrieri1
Igor Mishustin 2; Stefano Lottini 2
1 JW Goethe Universitat, Frankfurt 2 FIAS
1 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
We argue that a so far neglected dimensionless scale, the number of neighbors in a closely packed system (Nn, Nn~10 in our world), is relevant for the convergence of the large number of colors (Nc, Nc=3 in our world) expansion at large chemical potential. Using a highly simplified but universal model, we demonstrate that theNc≫Nn limit is qualitatively different from our world’s Nc≪Nn. In particular, the relationship between deconfinement and per- colation, and the in-medium modification of baryonic wavefunctions, are very different in these two regimes. We explore phenomenological consequences of these findings, particularly in regard to the new “Quarkyonic” phases conjectured from large Nc arguments and the problem of chiral symmetry breaking at high chemical potential Based on developments from Phys.Rev.C82:055202,2010 and http://arxiv.org/abs/1103.4824
111 / 40 Soft-quark bremsstrahlung and energy losses
Yuri Markov1
Margarita Markova 1
1 Institute for System Dynamics and Control Theory
Within the framework of a semiclassical approximation the general theory of calculation of effective currents and sources generating bremsstrahlung of an arbitrary number of soft quarks and soft glu- ons at collision of a high-energy color-charged particle with thermal partons in a hot quark-gluon plasma, is developed. For the case of one- and two-scattering thermal partons with radiation of one or two soft excitations, the effective currents and sources are calculated in an explicit form.In the model case of ‘frozen’ medium, approximate expressions for energy losses induced by the most simple processes of bremsstrahlung of soft quark and soft gluon, are derived.
120 / 41 On the fluctuation-dissipation theorem for soft fermionic excita- tions in a hot QCD plasma
Margaret Markova1
Yuri Markov 1
1 Institute for System Dynamics and Control Theory
Two ways of deriving the fluctuation-dissipation theorem (FDT) for soft fermion excitations ina hot non-Abelian plasma being in a thermal equilibrium are discussed. The first of them is based on the extended (pseudo)classical model in describing a quark-gluon suggested by us, while the second one rests on the standard technique of calculation of the FDT for thermodynamically equilibrium systems. It is shown that the full accounting all subtleties that are common to the fermion system under consideration , results in perfect coincidence of thus obtained FDTs. This provides a rather strong argument for the validity of the pseudoclassical model suggested.
2 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Theory developments / 42
Next-to-leading order structure function for DIS off a large nu- cleus
Giovanni Antonio Chirilli1
1 Lawrence Berkeley National Laboratory (LBNL)
The high-energy behavior of amplitudes in gauge theories can be reformulated interms of the evolution of Wilson-line operators. In the leading order this evolution is governed by the non-linear Balitsky-Kovchegov (BK) equation. In order to see if this equation is relevant for existing or future DIS accelerators (like EIC or LeHC) one needs to know how large are the next-to-leading order (NLO) corrections. In addition, the NLO corrections define the scale of the running-coupling constant in the BK equation and therefore determine the magnitude of the leading-order cross sections. To obtain then the structure function for DIS off a large nucleus at the NLO accuracy in αs, we calculate the NLO contribution to the BK equation and the NLO photon impact factor, related to the probability of the virtual photon to split in a quark anti-quark pair before scattering off the target. We obtain for the first time an analytic expression in coordinate space of the NLO photon impact factor.
Jets / 43
Higher harmonic jet tomography as a probe of fluctuating initial condition geometries in A+A
Barbara Betz1 Giorgio Torrieri 2; Miklos Gyulassy 1
1 Columbia University 2 Frankfurt Institute for Advanced Studies
While 2nd Fourier harmonics of jet quenching have been thoroughly explored in the literature and shown to be sensitive to (1) the underlying jet path length dependence of energy loss and (2) the differences between the mean eccentricity predicted by Glauber and CGC/KLN models ofinitial conditions, the sensitivity of higher harmonics, v_n(p_T, b), to differences between the fluctuation spectrum of geometries has remained relatively unexplored. We demonstrate that higher azimuthal jet harmonics (n>2) of R_AA(p_T,phi) and I_AA(p_T,phi) are remarkably insensitive to the differences of geometrical density fluctuations comparing between Glauber and CGC/KLN models of the initial conditions. Therefore, the differential elliptic v_2(p_T) vs. v_2^(I_AA)(p_T) mo- ment correlation between the 2nd moment of monojet R_AA and dijet I_AA nuclear modifications factors remains the most sensitive probe to differentiate between Glauber and CGC/KLN initial state sQGP geometries.
1 / 44 Flow-Driven Conical Correlations in Heavy-Ion Collisions
3 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Barbara Betz1 Dirk-H. Rischke 2; Giorgio Torrieri 3; Jorge Noronha 1; Miklos Gyulassy 1
1 Columbia University 2 Frankfurt University 3 Frankfurt Institute for Advanced Studies
We use (3+1)-dimensional hydrodynamic simulations to describe the propagation of a jet through an opaque medium and to investigate the underlying jet-medium interactions. We discuss that the double-peaked structure seen in the two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC), suggested as a signal for the creation of a Mach cone, can arise due to the averaging over many events in a transversally expanding back- ground. We find that the jet-induced away-side yields are quite insensitive to different energyand momentum loss scenarios, different jet velocities, and system sizes. Our claim can be experimentally distinguished from a ‘true’ Mach cone by analyzing hard-soft correlations induced by heavy-flavor jets, in particular by verifying that the double-peak structure stays the same even if the heavy quarks move subsonically.
121 / 45 The Single Flavor Color Superconductivity in a Magnetic Field.
Bo Feng1; Defu Hou2; Ping-Ping Wu2; Ren Hai-cang3
1 University od Texas at El Paso 2 Central China Normal University 3 Rockefeller University
[email protected], [email protected]
We investigate the single flavor color superconductivity in a magnetic field. Because of the absence of the electromagnetic Meissner effect, forming a nonspherical CSC phase, polar, A or planar, does not cost energy of excluding magnetic flux. We found that these nonspherical phases do occupya significant portion of the phase diagram with respect to magnetic field and temperature andmaybe implemented under the typical quark density and the magnetic field inside a compact star. Published in Phys.Rev.Lett.105:042001,2010.
39 / 46 The Subleading Term of the Strong Coupling Expansion ofthe Heavy-Quark Potential
Defu Hou1; Ren Hai-cang2; Shao-xia Chu1; Zi-Qiang Zhang1
1 Central China Normal University 2 Rockefeller University
[email protected], [email protected], [email protected]
Applying the AdS/CFT correspondence, the expansion of the heavy-quark potential of the calN supersymmetric Yang-Mills
4 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
theory at large Nc is carried out to the sub-leading term in the large ‘t Hooft coupling at both zero and nonzero temperatures. The strong coupling corresponds to the semi-classical expansion of the string-sigma model, the gravity dual of the Wilson loop operator, with the sub-leading term expressed in terms of functional determinants of fluctuations. The contribution of these determinants are evaluated numerically.
2 / 47 Mach Cone Induced by γ-Triggered Jets in High-Energy Heavy- Ion Collisions
Yan Zhu1
1 University of Bielefeld
Medium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to give rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such a deflection is the strongest for hadron-triggered jets which are often produced close to the surface of a dense medium due to trigger bias and travel against or tangential to the radial flow. Without such trigger bias, the effect of deflection on γ-jet showers and their medium excitation is weaker. Comparative study of hadron and γ-triggered particle correlations can therefore reveal the dynamics of jet-induced medium excitation in high-energy heavy-ion collisions.
Global and collective dynamics / 49
The second act of hydro: shocks and sounds from initial pertur- bations and jets
Edward Shuryak1
1 Stony Brook University
Recently there was significant progress in account for several lower harmonics of the Little Bang”, especially the so called triangular flow, ascribed to fluctuations of the initial conditions. We discuss this problem more generally, combining many harmonics coherently into certain patterns of sound propagation. Analytic solution for all harmonics is found for the so calledGubser flow”, with complete Green function obtained. Another source of perturbations which can be studied using our results are waves induced by quenching jets. We argue that for large energy loss shock waves should form, as well as the so called jet/fireball edge, separating unperturbed and excited matter. We discuss how this edge should be visible experimentally, perhaps on \ event-by-event basis.
52 / 51
5 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Viscous QCD matter at RHIC and LHC energies. Insights from viscous hydrodynamics + hadron cascade hybrid approach
Huichao Song1
Steffen Bass 2; Tetsufumi Hirano 3; Ulrich Heinz 4
1 Lawrence Berkeley National Laboratory 2 Duke University 3 The University of Tokyo 4 The Ohio State University
We present recent results from the newly developed hybrid code VISHNU [1] which couples viscous hydrodynamics for the quark-gluon plasma (QGP) with a hadron cascade model for the late hadronic stage. By describing the hadronic rescattering and freeze-out stage microscopically, we improve on earlier purely hydrodynamic models which required additional adjustable parameters to describe the transport and freeze-out characteristics of the hadron phase. By describing the QGP phase as a viscous rather than ideal fluid (as done in previous macroscopic + macroscopic hybrid codes), we account for the non-zero viscosity of the quark-gluon plasma which we can now determine empirically, without contamination from an incomplete treatment of the late hadronic dynamics, by comparing VISHNU results with experimental elliptic flow data. Using the Monte-Carlo-Glauber or Monte-Carlo-KLN models to generate event by event fluctuating initial entropy density profiles and averaging these profiles ei- ther in the reaction-plane (i.e. directly) or in the participant-plane (i.e. after recentering and rotating each event so that the main axes of its entropy density align), we generate smooth average initial conditions for viscous hydrodynamics which account in different ways for the event by event fluc- tuations in shape and orientation of the initial state of the collision fireball [2]. We find that the eccentricity scaled elliptic flow v2/ϵ is a universal function of charged multiplicity per unit overlap area (1/S)(dNch/dy) that depends only on the QGP viscosity but not on the initialization models [3]. Comparing these universal curves with experimental measurements we find that the specific QGP viscosity (η/s)QGP is constrained to fall in the range 1 < 4π(η/s)QGP < 2.5 where the width of this range is entirely dominated by model uncertainties for the initial eccentricities [3]. Compared to analysis based on pure viscous hydrodynamics this reduces the previously quoted robust upper limit for (η/s)QGP by a factor 2.5. The same (η/s)QGP values extracted in [3] from the centrality dependence of the pT -integrated elliptic flow of all charged hadrons also provide, for the first time,a consistently good simultaneous description of the pT spectra and differential elliptic flow v2(pT ) for charged hadrons as well as identified pions and protons over the entire range of collision centralities in 200 A GeV Au+Au collisions [4]. [1] H. Song, S. Bass and U. Heinz, Phys. Rev. C, in press [arXiv:1012.0555]. [2] T. Hirano and Y. Nara, Phys. Rev. C79, 064904,(2009). [3] H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, arXiv:1011.2783 [nucl-th]. [4] H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, arXiv:1101.4638 [nucl-th].
112 / 52
Non-Extensive Approach to High-Energy Collisions
Gergely Barnafoldi1
Gergely Kalmár 2; Károly Ürmössy 2; Tamás S. Biró 1
1 KFKI Research Institute for Particle and Nuclear Physics of the HAS 2 Eötvös University
6 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Non-extensive thermodynamics is a novel and promising tool for the statistical interpretation of high energy phenomena. In particular the experimental systems are far from the familiar canonical state. On the basis of generalized entropy and energy composition rules also Tsallis–Pareto-like distributions can be obtained. Such distributions reproduce extremely well the various transverse momentum spectra in hadron-hadron collisions and in cosmic rays. However, the derivation and the correct interpretation of the Tsallis-Renyi parameter are still unsolved questions. We investigated several models to discover the non-extensive phenomena behind hadronization. Here we present our results for (i) a possible microcanonical generalization of the Tsallis distribution in e+e- collision, and (ii) the original Tallis Pareto-like distribution including QCD evolution ansatz for the hadronization process.
3 / 53 Momentum broadening in weakly coupled quark-gluon plasmas
Mindaugas Lekaveckas1
Christopher Lee 1; Francesco D’Eramo 1; Krishna Rajagopal 1; Liu Hong 1
1 MIT
Jet quenching parameter is an important quantity in order to understand energy losses in heavy ion collisions and to get insights into properties of deconfined quark-gluon plasmas. Soft Collinear Effective theory provides framework to define momentum broadening of probing quark/gluon and thus define jet quenching parameter as the expectation value of two space-like separated light-like Wilson lines which can be eval- uated for the desired medium. In this work we evaluate jet quenching parameter at weak coupling for quark-gluon plasmas in thermal equilibrium using Hard Thermal Loop resummed effective thermal field theory.
4 / 54 Radial and elliptic flow in LHC Pb+Pb collisions from viscous hy- drodynamics
Chun Shen1
Ulrich Heinz 1
1 The Ohio State University
Predictions and postdictions from viscous hydrodynamics for the transverse momentum spectra and differential elliptic flow for unidentified and identified charged hadrons from Pb+Pb collisions at LHC energies, including their centrality dependence, will be presented. These predictions are based on a global viscous hydrodynamic fit of soft hadron spectra and their anisotropies measured in Au+Au collisions at RHIC, using a state-of-the-art equation of state, which accurately reproduces the observed charged hadron, pion and proton spectra and their differential v_2(p_T) for all col- lision centralities in the range p_T<2 GeV. Assuming the same specific effective shear viscosity eta/s=0.20 for KLN initial conditions at RHIC and LHC, we obtain a good description of the soft charged hadron spectra in central Pb+Pb collisions at sqrt{s}=2.76 A TeV, but slightly overpredict the integrated charged hadron elliptic flow in measured by the ALICE Collaboration in non-central
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Pb+Pb collisions. We explore whether and how this can be remedied by allowing for a tempera- ture dependent change of the specific shear viscosity eta/s of the quark-gluon plasma in thenewly explored higher temperature region probed at the LHC. In doing so, we expose a need for a more quantitative understanding of the early pre-equilibrium stage. Future comparisons of spectra and elliptic flow for identified hadrons at both sqrt{s}=2.76 and 5.5 A TeV with predictions presentedin this talk will allow to further test the validity of the viscous hydrodynamic model and will shed additional light on possible variations of the quark-gluon transport coefficients between RHIC and LHC energies.
94 / 55 Direct Photons from microscopic+macroscopic hybrid model
Bjørn Bäuchle1
Marcus Bleicher 1
1 Frankfurt Institute for Advanced Studies
The microscopic transport model UrQMD and a micro+macro hybrid model are used to calculate direct photon spectra from A+A-collisions at FAIR- and RHIC-energies. In the hybrid model, the intermediate high-density part of the nuclear interaction is described with ideal 3+1-dimensional hydrodynamics, while the initial state and final state-scatterings are modelled in UrQMD. Different Equations of State of the matter created in the heavy-ion collisions are investigated and the resulting spectra of direct photons are shown. The emission patterns of direct photons in space and timeare discussed.
Heavy Flavors / 56
Massive QCD antenna radiation in medium
Hao Ma1
Carlos Salgado 1; Konrad Tywoniuk 2; Néstor Armesto 1; Yacine Mehtar-Tani 1
1 Universidad de Santiago de Compostela 2 Lund University
Medium modifications of jets have previously been thoroughly studied by calculating the gluon radi- ation spectrum off a highly energetic quark traversing a hot and dense QCD medium. But thestudy of the interference effects, the building block of the QCD jet calculation in vacuum, between different radiators has been missing for quite a long time. In this work we calculate, in the eikonal approxima- tion, the gluon radiation spectrum off a quark-antiquark antenna passing through a deconfined QCD plasma with the masses of the quark and antiquark turned on. The massive quark-antiquark antenna involves both the dead cone effect and the Landau-Pomeranchuk-Migdal (LPM) effect, and takes into account the correlation between both of the emitters leading to an additional strong suppression of gluon radiation at angles smaller than the opening angle of the quark-antiquark pair. Furthermore, the quark-antiquark antenna spectrum is infrared divergent. We calculate the medium-induced en- ergy loss of heavy quarks (charm and bottom) and compare it to well-known results (BDMPS/GLV). The implications on jet quenching observables in heavy ion collisions are also discussed.
Global and collective dynamics / 57
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The QGP shear viscosity: elusive goal or just around the corner?
Ulrich Heinz1
1 The Ohio State University
[email protected], [email protected]
The last two years have seen tremendous progress in the theoretical tools for extracting thespecific shear viscosity of the quark-gluon plasma in the temperature range explored by heavy-ion collisions at RHIC and LHC. The effects of viscosity on the transverse momentum spectra and differential ellip- tic flow and their interplay with other hydrodynamic parameters have been studied systematically [1]. A global viscous hydrodynamic fit to charged and identified hadron spectra and elliptic flow at all collision centralities in RHIC Au+Au collisions has been shown to successfully extrapolate to Pb+Pb collisions at the LHC [2], providing a rather good first description of the elliptic flow measured by the ALICE collaboration. Viscous relativistic hydrodynamics has been coupled to a microscopic description of the late hadronic rescattering and freeze-out stage [3,4], thus eliminating previous large uncertainties arising from strong dissipative effects in the hadronic phase [5] and allowing for a first tightly constrained extraction of the QGP shear viscosity from RHIC data [3,6]. Thelargest remaining uncertainty arises from poor theoretical control over the initial spatial eccentricity of the collision fireball, and a lack of prospects to more tightly constrain this initial deformation theoret- ically appears to make progress towards further increased empirical precision for the QGP shear viscosity elusive. Recent studies of higher harmonic eccentricity and flow coefficients [7] and their fluctuations from collision to collision using event-by-event hydrodynamics provide, however, a novel angle that may allow to settle this question experimentally. This will be the main focus ofmy talk. [1] Chun Shen, U. Heinz, P. Huovinen, H. Song, Phys. Rev. C82, 054904 (2010). [2] Chun Shen, U. Heinz, et al., “Radial and elliptic flow in Pb+Pb collisions at the Large Hadron Collider from viscous hydrodynamics,” to be published. [3] H. Song, S. A. Bass, U. Heinz, T. Hirano and Chun Shen, arXiv:1011.2783. [4] H. Song, S. Bass and U. Heinz, Phys. Rev. C, in press [arXiv:1012.0555]. [5] Chun Shen and U. Heinz, arXiv:1101.3703 [6] H. Song, S. Bass, U. Heinz, T. Hirano and Chun Shen, arXiv:1101.4638 [nucl-th]. [7] Zhi Qiu and U. Heinz, “Event-by-event shape and flow fluctuations in RHIC fireballs,” to bepub- lished.
Jets / 59
Jet shower evolution in medium and di-jet asymmetry in PbPb collisions at the LHC
Guang-You Qin1
Muller Berndt 1
1 Duke University
We study the evolution of a partonic jet shower propagating through a hot quark-gluon plasma. A differential equation is derived the evolution of the radiated gluon distribution as the jet propagates through the medium. Combined with the in-medium evolution of the leading parton, we compute the depletion of the energy from the jet cone by dissipation through elastic collisions with medium constituents, by scattering of shower partons to larger angles, and by radiation outside the jetcone. Numerical results are presented for the nuclear modification of di-jet energy asymmetry in Pb+Pb collisions at the LHC.
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4 / 61 Experimental study of quark and gluon jets in proton-proton and heavy-ion collisions.
Sona Pochybova1
1 KFKI Research Institute for Particle and Nuclear Physics-Hungari
We propose a set of jet-energy dependent cuts to be used to distinguish between quark and gluon jets experimentally based on a Monte-Carlo study of their properties. Using these cuts we are able to achieve up to 80% purity of our selection. Further, we introduce the possibility to calibrate these cuts via gamma-jet and multi-jet events, which represent clean production channels for quark and gluon jets, respectively. The calibration can happen on real data and thus, reduces the dependence of the method performance on Monte-Carlo model predictions. We present the π, K and p spectra for quark and gluon jets in generated proton-proton and Pb-Pb collisions at STAR and LHC energies.
113 / 63 Simulations of thermodynamic and kinetic properties of the strongly coupled quark-gluon plasma
Vladimir Filinov1 Michael Bonitz 2; Pavel Levashov 1; Vladimir Fortov 1; Yurii Ivanov 3
1 Joint Institute for High Temperatures, Russian Academy of Sciences, Russia 2 Institute for Theoretical Physics and Astrophysics, , Kiel, Germany 3 GSI Helmholtzzentrum fur Schwerionenforschung GmbH,Darmstadt, Germany
In recent years, there has been an increasing interest in dynamics and thermodynamics of non- Abelian plasmas at both very high temperature and density. It is expected that a specific state of matter with unconfined quarks and gluons - the so called quark - gluon plasma (QGP) -canexist.The most fundamental way to compute properties of the strongly interacting matter is provided by the lattice QCD. Interpretation of these very complicated computations requires application ofvarious QCD motivated, albeit schematic, models simulating various aspects of the full theory. Moreover, such models are needed in cases when the lattice QCD fails, e.g. at large baryon chemical potentials and out of equilibrium. A semi-classical approximation, based on a point like quasi-particle picture has been recently introduced in literature. It is expected that it allows to treat soft processes in the QGP which are not accessible by the perturbative means and the main features of non-Abelian plasmas can be understood in simple semi-classical terms without the difficulties inherent to a full quantum field theoretical analysis. Here we propose stochastic simulation of thermodynamics and kinetic properties for QGP in semi- classical approximation in the wide region of temperature, density and quasi-particles masses. We extend previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime and take into account the Fermi (Bose) statistics of quarks (gluons) and quantum degeneracy self-consistently. In grand canonical ensemble for finite and zero baryon chemical potential we use the direct quantum path integral Monte Carlo method (PIMC) developed for finite temperature within Feynman formu- lation of quantum mechanics to do calculations of internal energy, pressure and pair correlation functions. The QGP quasi-particles representing dressed quarks, antiquarks and gluons interact via color quantum Kelbg pseudopotential rigorously derived in for Coulomb particles. This method has been successfully applied to strongly coupled electrodynamic plasmas (EMP) . A strongly correlated behavior of the QGP is expected to show up in long-ranged spatial correlations of quarks and glu- ons which, in fact, may give rise to liquid-like and, possibly, solid-like structures. This expectation
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is based on a very similar behavior observed in electrodynamic plasmas. We have done already the first calculation of the QGP equation of state, spatial and color pairdis- tribution functions, diffusion coefficients and shear viscosity. The preliminary results hasalready been reported and discussed at the international conferences and meetings and are accepted for publications.
5 / 64 Direct jet reconstruction in d+Au collisions at PHENIX
Dennis Perepelitsa1
1 Columbia University
d+Au collisions at RHIC can be used to investigate cold nuclear matter effects on hard parton scatter- ing. d+Au collisions at different centrality (different N_coll) can probe nuclear parton distributions, initial state energy loss and final state parton interactions in the cold nucleus. They also provide a valuable baseline for hard-scattering processes in heavy ion collisions. Measurements using jet reconstruction may provide a more sensitive probe of the parton level physics than inclusive single- particle measurements or two-particle correlations. We present the current results from direct jet reconstruction at PHENIX in d+Au collisions at sqrt(s) = 200 GeV. We discuss some of the challenges of direct jet reconstruction in a high-multiplicity heavy ion environment.
66 Upsilon production at RHIC and LHC
Pengfei Zhuang1
Nu Xu 2; Yunpeng Liu 1
1 Tsinghua University 2 China Center Normal University
[email protected], [email protected], [email protected]
Upsilon production in heavy ion collisions at RHIC energy is investigated. While the transverse mo- mentum spectra of the ground state Upsilon(1s) are controlled by the initial state Cronin effect, the excited (b b-bar) states are characterized by the competition between the cold and hot nuclear matter effects and sensitive to the dissociation temperatures determined by the heavy quark potential. We emphasize that it is necessary to measure the excited heavy quark states in order to extract the early stage information in high energy nuclear collisions at RHIC.
6 / 67 Non-extensive Statistical Approach to Fragmentation
Karoly Uermoessy1
Gergely Gabor Barnafoldi 2; Tamas Sandor Biro 2
1 Dept. for Theor. Phys., ELTE; Research Institute for Particle and Nuclear Physics (KFKI) 2 Research Institute for Particle and Nuclear Physics (KFKI)
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The first part of this talk presents a possible statistical physical description of hadron productionin electron-positron collisions. The main idea of the model is that hadrons produced inside a jet maybe considered as a microcanonical ensemble, with multiplicity fluctuating event by event. The obtained hadron spectrum is in good agreement with measured fragmentation functions [1]. Furthermore, at low energies, the above hadron spectrum coincides with the Tsallis distribution, which gives good fittings to hadron spectra stemming from proton-proton and nucleus-nucleus col- lisions. In the second part of the talk, I provide mathematical proof for the energence of the Tsallis distribution in systems with special interactions, and present results of a parton collision cascade simulation based on these interactions [2]. [1] Karoly Urmossy, Gergely Gabor Barnafoldi, Tamas Sandor Biro, Generalised Tsallis Statistics in Electron-Positron Collisions arXiv:1101.3023 (Submitted to PLB) [2] Karoly Urmossy, Tamas S. Biro, Gergely G. Barnaföldi Pion Production Via Resonance Decay in a Non-extensive Quark-Gluon Medium with Non-additive Energy Composition Rule arXiv:1101.3522 (Proceedings of Hot and Cold Baryonic Matter 2010)
Theory developments / 68
Equilibration and Thermalization of Strongly Coupled Field The- ories
Berndt Mueller1
Alice Bernamonti 2; Andreas Schaefer 3; Ben Craps 2; Esko Keski-Vakkuri 4; Jan de Boer 5; Masaki Shigemori 6; Neil Copland 2; Vijay Balasubramanian 7; Wieland Staessens 2
1 Duke University 2 Vrije Universiteit Brussel 3 Universitaet Regensburg 4 Helsinki Institute of Physics 5 University of Amsterdam 6 Nagoya University 7 University of Pennsylvania
Using the AdS/CFT correspondence, we probe the scale-dependence of thermalization in strongly coupled field theories following a quench, via calculations of 2-point functions, Wilson loopsand entanglement entropy in 2, 3, and 4 dimensions. In the saddlepoint approximation these probes are computed in AdS space in terms of invariant geometric objects – geodesics, minimal surfaces and minimal volumes. Our calculations for two dimensional field theories are analytical. In our strongly coupled setting, all probes in all dimensions share certain universal features in their ther- malization: (1) a slight delay in the onset of thermalization, (2) an apparent non-analyticity at the endpoint of thermalization, (3) top-down thermalization where the UV thermalizes first. For homo- geneous initial conditions the entanglement entropy thermalizes slowest, and sets a time scale for equilibration that saturates a causality bound over the range of scales studied. The growth rate of entanglement entropy density is nearly volume-independent for small volumes, but slows for larger volumes.
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Strong Coupled Pion Superfluid
Yin Jiang1
Ke Ren 1; Pengfei Zhuang 1; Tao Xia 1
1 Tsinghua University
[email protected], [email protected]
We calculate the meson screening mass and quark potential in a pion superfluid in the frame of Nambu–Jona-Lasinio model. Themost strong potential is always located at the critical point of pion superfluid along any of the axes of temperature and baryon and isospin chemical potentials. Unlike the temperature and baryon density effect, the potential can not be efficiently suppressed in the pion superfluid and the quark matter is always in astrongly coupled phase even at extremely high isospin density.
Pre equilibrium and initial stage and global collective dynamics / 71
Bulk properties of PbPb collisions at the LHC measured by AL- ICE
Global variables, such as the charged particle multiplicity and the transverse energy are important observables to characterize Relativistic Heavy Ion collisions and to constrain model calculations. The charged-particle multiplicity dNch/deta(eta=0) and transverse energy dEt/deta(eta=0) aremea- sured at sqrt(s_NN)=2.76TeV in Pb-Pb collisions as a function of centrality and in p-p collisions. The fraction of inelastic cross section seen by the ALICE detector is calculated either using a Glauber model or the data corrected by simulations of nuclear and EM processes, or data collected with a minimum bias interaction trigger. The centrality, defined by the number of nucleons participating in the collision, is obtaine, via the Glauber model, by relating the multiplicity distributions of various detectors in the ALICE Central Barrel and their correlation with the spectator energy measured by the Zero-Degree Calorimeters. The results are compared to corresponding results obtained at the significantly lower energiesof the BNL AGS, the CERN SPS, and the BNL RHIC, and with models based on different mechanisms for particle production in nuclear collisions. Particular emphasis will be given to a discussion on systematic studies of the dependence of the centrality determination on the Glauber model, and the validity of the Glauber model at unprecedented collision energies.
Pre equilibrium and initial stage and global collective dynamics / 72
Common discussion with 3 speakers
Global collective dynamics / 73
Anisotropic flow from ALICE
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We report on the measurements of anisotropic flow with the ALICE detector at the LHC. For charged particles we present the first triangular, quadrangular and pentagonal flow measurements. Theflow of charged and identified particles is compared to hydrodynamic model predictions at low-p_t and for identified particles at intermediate-p_t the so-called number of constituent quark scaling isin- vestigated. At higher transverse momentum we compare the elliptic flow results with expectation from parton energy loss. For the integrated elliptic flow we show the scaling with the initial eccentricity and we quantify the magnitude of the event by event fluctuations. These results indicate strong collective flow and are consistent with expectations for the createdhot and dense system created at the LHC.
Global collective dynamics / 74
Flow measurements from the CMS experiment
We report on the CMS measurements of charged hadron anisotropic azimuthal distributions from PbPb collisions at √sNN= 2.76 TeV and their decomposition into a Fourier series up to the 6th coefficient. The results are presented as a function of transverse momentum, centrality and pseudorapidity and cover a broad kinematic range. The relation between the different harmonic coefficients and the scaling with the respective participant eccentricity are studied. These results could provide constraints on the theoretical description of the early dynamics in the hot and dense medium and its transport properties.
Hard probes I: hadron spectra / 75
Quenching of single hadron and photon spectra from RHICto LHC
I will discuss the generic features of parton energy loss effects on the quenching of large-pT hadrons, as well as more quantitative studies. The differences expected from RHIC to LHC will be highlighted. The quenching of prompt photons will also be discussed in detail. Finally, I will stress the needfor precise baseline measurements of hadrons and photons in pp and pPb collisions.
Hard probes I: hadron spectra / 76
Particle production at large transverse momentum with ALICE
We present transverse momentum distributions of charged particles and identified hadrons in pp and Pb-Pb collisions, measured by ALICE at the LHC. The Pb-Pb data are presented in intervals of the collision centrality and cover transverse momenta up to 50 GeV/c. Nuclear medium effects are
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studied in terms of the nuclear modification factor R_AA. The results indicate strong suppression of high-p_T particles in Pb-Pb collisions, consistent with a large energy loss of hard-scattered partons in the hot, dense, and long-lived medium created at the LHC.
Hard probes II: true jets / 77
Monte Carlo tools for jet quenching
Hard probes II: true jets / 78
STAR on reconstructed jets and jet-like correlations
Heavy flavor and Quarkonia in medium / 79
Applying the AdS/CFT correspondence to non-abelian plasmas
Heavy flavor and Quarkonia in medium / 80
PHENIX heavy flavor
Heavy flavor and Quarkonia in medium / 81
Quarkonia measurements by the CMS experiment in pp and PbPb collisions
CMS is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Such probes are especially relevant for studying the quark gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. Quarkonia and bottomonia are sensitive to the evolution of the medium.In particular, the Jψ production in heavy ion collisions has been studied at different energies and with different collision systems without yet givinga global picture that is fully understood. Measuring the charmonium production at the LHC energies in PbPb collisions will help constraining predictions, in particular those expecting high recombination of prompt J/Psi or
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suppression in hot medium. We will review CMS J/Psi measurements in pp collisions at √sNN=7~TeV, which allow precision studies of quarkonia production and serve as a reference for the observation of hot nuclear effects. CMS is able to distinguish non-prompt J/psi from prompt J/psi in PbPb collisions, and will present the prompt J/psi production cross-section in PbPb inclusively and as a function of transverse momentum, rapidity and number of nucleons participating in the collision. Finally, we compare the B fraction measured in PbPb collisions with that measured in pp at various energies. The LHC centre-of-mass energy allows copious Y production in PbPb collisions. Detailed measurements of bottomonium will help characterize the dense matter produced in heavy-ion collisions beyond what was accessible at RHIC (mostly) with charmonia. The full spectroscopy of quarkonium states has been suggested as a possible thermometer for the QGP. With its excellent dimuon mass resolution, CMS has measured the three Y states in pp collisions. With the 2010 PbPb data sample, CMS has observed the Y(1S) as well as excited states. The Υ(1S) cross-section is presented as a function of transverse momentum, rapidity and centrality, and excited state. Suppression of the excited state in PbPb will be discussed.
82
Theory
Electromagnetic probes
83
Experiments
Photons and dileptons
84
Theory
AdS/CFT, more
85
Theory
Lattice QCD
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86
Experiments
Hadrochemistry
Correlations & fluctuations / 87
Correlations and fluctuations from lattice QCD
88 p + A
89
New challenges at the low energy frontier
SPS, FAIR, low energy RHIC, NICA/MPD (experiments and theory)
90 e + A
New challenges / 91
The high energy frontier of A-A
Theory developments / 92
Non-conformal holography of light and heavy quark jet quench- ing at RHIC and LHC
Andrej Ficnar1
Jorge Noronha 2; Miklos Gyulassy 1
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1 Columbia University, New York, USA 2 Universidade de Sao Paulo, Sao Paulo, Brazil
We investigate the connection between the conformal anomaly in the confinement transition region and quenching of heavy and light quarks in heavy ion collisions at RHIC and LHC by using a new non-conformal holographic model with a dilaton field. Holographic thermodynamic properties of the sQGP are constrained by lattice QCD calculations. The string drag force model of jets isgen- eralized to include both trailing and falling string scenarios. We compare the differential nuclear modification of light and heavy quark jets predicted by this model emphasizing the novelquark mass and energy dependence through the confinement transition region.
7 / 93 Jet Modification Via The LPM Effect In Infinite Quark Matter
Christopher Coleman-Smith1
1 Duke Physics
[email protected] √ Recent results for Pb+Pb collisions at sNN = 2.76~TeV from the LHC have shown dramatic di-jet asymmetry, implying a strong medium modification of jets as they pass through the QGP. A fully-relativistic Monte-Carlo Boltzmann transport code, the Parton Cascade Model (PCM), is used to simulate the development of a jet in a partonic medium. The PCM includes collisional and radiative processes and a local probabilistic implementation of the Landau-Pomeranchuck-Migdal (LPM) effect. The PCM is particularly suitable for the examination of jet modification as it treats both mediumand jet partons on an equal footing, allowing for full tracking of the process. We present the first infinite matter results, including an accurate treatment of the LPM effect, for the energy flow within the jet cone alongside results for the rate at which energy lost from the jet is deposited back into the medium. We also apply our simulation to the observed ATLAS dijet asymmetry.
8 / 94 Measuring parton energy loss at RHIC
Michael Tannenbaum1
1 Brookhaven National Laboratory (BNL)-Unknown-Unknown
The method of measuring xˆh, the ratio of pˆT a, the away-parton pT , to pˆT t, the trigger-parton pT , using two-particle correlations at RHIC, which is sensitive to the away parton energy loss due to the surface bias, will be reviewed. This measurement is simply related to the new variable introduced at LHC for the di-jet transverse momentum imbalance, AJ = (ˆpT t − pˆT a)/(ˆpT t +p ˆT a) = (1 − xˆh)/(1 +x ˆh). Results from two-particle correlations at RHIC for xˆh = (1 − AJ )/(1 + AJ ) will be reviewed and new results will be presented and compared to LHC measurements using jets.
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9 / 95 Dynamical magnetic effects and the nonphotonic electron puzzle at RHIC
Alessandro Buzzatti1
Miklos Gyulassy 1
1 Columbia University
[email protected], [email protected]
Perturbative magnetic scattering effects in the HTL approximation predict enhanced jet energy loss for both light and heavy quarks. Whereas this helps to reduce the discrepancy of pQCD tomography with single electron data at RHIC, the new computations reveal significant disagreement with pion quenching data due to overestimation of the quenching suffered by light jets. We discuss whether this is sufficient to rule out the HTL approximation of the QGP medium. The role of futureflavor tagged charm and bottom jet observables at RHIC and LHC is emphasized.
Overviews / 96
Overview of the experimental results by the ALICE Collabora- tion
In this talk we summarize the results obtained by ALICE Collaboration in the first Pb-Pb run at LHC.
Overviews / 97
Results from lead-lead collisions with the ATLAS Detector at the LHC
Overviews / 98
Overview of the experimental results by the CMS Collaboration
We will present early results of the CMS experiment from PbPb collisions at √sNN = 2.76 TeV, probing quark and gluon matter at unprecedented values of energy density. The capabilities of the CMS apparatus allows usto investigate various hard probes, as well as bulk particle production and collective phenomena, using the calorimetry, muon and tracking systems covering a large range in pseudorapidity, complemented by a flexible two-level trigger system.
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Overviews / 99
PHENIX Highlights
After establishing the creation of dense partonic matter in theearly years of RHIC, the focus of recent experimental and theoretical effort has been to determine the properties of this partonic medium. With the advent of the LHC, there is now a new aspect to this quest: are the properties of the medium created at the LHC different from that created at RHIC? In this light, we will present the latest experimental results of the PHENIX collaboration, further constraining the properties of the sQGP at RHIC.
Overviews / 100
STAR highlights
101
Opening
Overviews / 102
LHC accelerator
Overviews / 103
Theory overview
Student lectures / 104
Heavy-ion collisions and QCD: the big picture
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Student lectures / 105
Soft physics and hydrodynamics
Student lectures / 106
Jets, high-pT hadrons and prompt photons
Student lectures / 107
Heavy-quarks and quarkonia
Famous plot session / 108
Initial conditions, low-x QCD, thermalization
david.d’[email protected]
Famous plot session / 109
QCD phase transition, hydrodynamics, hadronization
Famous plot session / 110
Jets, high-pT hadrons, and prompt photons
Famous plot session / 111
Heavy-quarks and quarkonia
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Jets / 112
Medium induced collinear radiation from soft collinear effective theory (SCET)
Francesco D’Eramo1; Hong Liu1; Krishna Rajagopal1
1 MIT
The propagation of hard partons through the strongly interacting matter created in highenergy heavy-ion collisions involves widely separated scales. The methods of Effective Field Theories (EFT) can provide a factorized description at lowest nontrivial order, and a formalism where the correction to this factorization are calculable systematically order by order in the small ratios between the different scales. In this talk I will present our recent results on the calculation of the spectrumof the gluons emitted by the hard parton, where the radiated gluons are collinear with the incoming hard parton and with arbitrary energy (not necessarily much softer than the energy of the hard parton). I will also briefly discuss how to extend the analysis to include the emission ofgluons collinear in arbitrary directions and gluons with all the components of their momentum scaling as the medium characteristic energy scale (soft gluons). In particular I will show how powerful concepts like collinear gauge invariance and reparameterization invariance simplify the derivation of the effective Lagrangian.
122 / 113 Suppression of the repulsive force in nuclear interactions near the chiral phase transition
Chihiro Sasaki1
Hyun Kyu Lee 2; Mannque Rho 3; Won-Gi Paeng 2
1 Frankfurt Institute for Advanced Studies 2 Hanyang University 3 CEA Saclay
One of the issues in hot/dense QCD is to understand the state of matter in the vicinity of phase transition from hadronic matter to quark matter expected to be created in heavy-ion collisions, or to be present in theinterior of compact stars. In nuclear physics, a scalar meson plays an essential role as known from Walecka model that works fairly well for phenomena near nuclear matter density. On the other hand, at high density, the relevant Lagrangian thathas correct symmetry is the linear sigma model, and the scalar needed there is the sigma that is the fourth component of the chiral four-vector. Thus in order to probe highly hot/dense matter, we have to figure out how the chiral scalar at low temperature/density transmutes to the fourth component of the four-vector. In this talk, we introduce a chiral scalar as a dilaton associated with broken conformal symmetry and responsible for the trace anomaly of QCD and discuss the properties of nuclear matter at high density [1]. As the “dilaton limit” is taken, which drives a system from nuclear matter density to near chiral restoration density, a linear sigma model emerges from the highly nonlinear structure with the omega meson decoupling from the nucleons. A striking prediction of this procedure is that as the dilaton limit is approached as density increases, the omega-nucleon interaction known to be repulsive at low density gets strongly suppressed at high density. The omega-mediated short-range repulsion gets also suppressed. This occurs inthe
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rho-meson exchanged repulsion too. Consequently the symmetry energy which plays a crucial role in the structure of compact stars gets suppressed. An immediate consequence would be that the equation of state (EoS) of dense matter will be softened at high density and would accommodate the EoS without any exotica consistent with the recent measurement of a 2-solar-mass neutron star. Reference: [1] Chihiro Sasaki, Hyun Kyu Lee, Won-Gi Paeng and Mannque Rho, “Conformal anomaly and the vector coupling in dense matter,” arXiv:1103.0184 [hep-ph].
115 Equation of state of a strongly-interacting QGP and charmonium suppression
binoy patra1
Vineet Agotiya 1
1 Indian Institute of Technology Roorkee
Recently we have developed the equation of state for a strongly interacting quark-gluon plasma in the framework of strongly-coupled QED plasma by incorporating the non-perturbative effects in terms of nonzero string tension in the deconfined plasma phase, unlike the Coulomb interactions alone. Our results on thermodynamic observables {\em viz.} pressure, energy density, speed of sound etc. nicely fit with the lattice equation of state for gluon, massless andas well {\em massive} flavored plasma. Motivated by this agreement with lattice results, we have employed our equation of state to estimate the quarkonium suppression in an expanding, dissipative strongly interacting QGP produced in relativistic heavy-ion collisions and our prediction matches exactly with the recent PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions at BNL RHIC. We have also predicted for the Υ suppression in Pb+Pb collisions at LHC energy which could be tested cleanly in the ALICE experiments at CERN LHC.
114 / 117 First-principles derivation of the jet energy-momentum deposi- tion source term in the QGP and its implications for shockwave formation at RHIC and at the LHC
Richard Neufeld1
1 LANL
I present a new derivation for the distribution of energy and momentum transmitted from a fast parton to a medium of thermalized quarks and gluons, or the source term. A thermal field theory approach enables the direct evaluation of the source term from the divergence of the QCD energy
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momentum tensor. This approach is more general than previously used Boltzmann transport tech- niques and allows for the coupling of realistic external quark and gluon currents to the Lagrangian of soft QCD matter. Specifically, I consider for the first time the medium response toback-to-back jets and jets + medium-induced gluon bremsstrahlung. The calculation includes the effects of quan- tum interference between the interactions of the multiple fast partons with the medium, and demon- strates that the energy absorbed by the medium is enhanced in a non-trivial way due to the presence and formation time of medium induced radiation. The numerical results suggest that the use of such realistic external currents has important implications for the shockwave formation in relativistic heavy ion collisions at RHIC and the LHC and soft-to-intermediate transverse momentum particle correlation phenomenology.
40 / 118
Momentum dependence of quarkonium production at RHIC and LHC
Yunpeng Liu1
Nu Xu 2; Pengfei Zhuang 1
1 Tsinghua University 2 CCNU (Central China Normal University)
[email protected], [email protected]
The momentum dependence of quarkonium dissociation temperature in hot medium is investigated and is applied to the quarkonium suppression in high energy nuclear collisions. For a fast moving quarkonium, the screening is significantly weaken, its dissociation temperature becomes higher and leads to a transverse momentum broadening in heavy ion collisions at RHIC and LHC.
69 / 120
Strong color fields effects and baryon/meson anomaly in p+p and central Pb+Pb collisions at L H C energies(*).
VASILE TOPOR POP1
Charles Gale 1; Jean Barrette 2; Miklos Gyulassy 3
1 McGill University, Montreal, Canada 2 McGILL UNIVERSITY, MONTREAL, CANADA 3 Columbia University, New York, USA
With the HIJING/BBar v2.0 event generator, we explore the phenomenological consequences of the suppression of perturbative quantum chromo-dynamics (pQCD) mini-jet production and of en- hanced “in medium” strong longitudinal color field. Nuclear effects like shadowing and parton en- ergy loss (”jet quenching”) are included. This analysis focuses on p+p collisions at centre of mass energy (sqrt(sNN)) 0.900, 2.36 and 7 TeV, and on central Pb+Pb collisions at sqrt(sNN) = 2.76 TeV, where recent data have been reported by LHC Collaborations (ALICE, ATLAS, CMS). The effective energy-dependent string tension values are constrained by p+p data from Relativistic Heavy Ion Collider (RHIC), the Tevatron, and recent Large Hadron Collider (LHC) runs. The pQCD
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cut-off value p0(s) is constrained by Au+Au collisions data from RHIC. Data on charged hadron multi- plicity and charged hadron nuclear modification factor (RAA) in central (0-5%) Pb+Pb collisions from the ALICE experiment at the LHC are used to constrain the main parameters of the “jet quenching” phenomena (energy loss and mean free path of initial parton-parton interactions). Predictions for the energy and centrality dependence of rapidity densities (2dNch/dy/Npart) and the hadron flavor dependence(mesons and baryons) of the nuclear modification factor RAA are presented. By study- ing baryon/meson ratios, we show that the jet quenching in central collisions suppresses the hard pQCD component of the particle spectra, thereby exposing a novel component of baryon dynamics that we attribute to (gluonic) baryon-anti-baryon junctions (JJbar). We predict that a baryon/mesons anomaly at intermediate transverse momentum values will persist at LHC energies, with a moderate centrality dependence. (*) This work is being supported by NSERC (Canada) and bythe US Department of Energy.
10 / 122 An effective theory for jet propagation in dense QCD matter: jet broadening, radiative energy loss and LHC phenomenology
grigory ovanesyan1
1 LANL
Soft Collinear Effective Theory (SCET) is a powerful toolto study jet physics. In order to describe jet propagation in the dense QCD matter created in ultra-relativistic nuclear collisions, SCET needs to be modified by the inclusion of the transverse to thejet axis gluon mode, which is commonly referred to as a Glauber gluon. We construct the Lagrangian of the resulting effective theory and demonstrate the gauge invariance of the jet broadening and radiative energy loss results. We show how using effective theory methods allows us to go beyond the soft gluon approximation, which is commonly used in the heavy-ion energy loss phenomenology. Our results are presented for realistic jet-medium scattering cross sections with fully dynamic QGP response. Finally, we discuss the implications of the newly-developed theory for LHC hard probes phenomenology with an emphasis on the quenching of leading particles and jets.
5 / 123 Directed Flow in event-by-event hydrodynamics
Fernando Gardim1 Frederique Grassi 1; Jean-Yves Ollitrault 2; Matthew Luzum 2; Yogiro Hama 1
1 USP 2 Saclay
Fluctuations in the initial geometry of a nucleus-nucleus collision have been recently shown to produce the correlation structures known as ridge” andshoulder”. These event-by-event
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fluctuations result in new types of anisotropic flow, suchas triangular flow v3 and a new type of directed flow v1, which, unlike the usual directed flow, is also present at midrapidity. The anisotropic flows due to the fluctuations inthe initial density profile result in different reference angles Ψn for every harmonic n, which are not necessarily correlated with the event plane angle Ψ2 (the elliptic flow reference angle), used by the experimentalists to measure the anisotropic flows, as v1, v2 and v4. Unlike triangular flow, this new v1 has not been studied in a hydrodynamic framework. This work is based on the first quantitative predictions forthis new v1 in Au-Au collisions at the top RHIC energy, using the hydrodynamic code NEXSPheRIO. NEXSPheRIO solves the relativistic ideal hydrodynamics using initial conditions provided by the event generator NeXus, providing good description for several observables, like elliptic flow. Shear viscosity is not implemented in this computation, though its effect should be smaller than higher harmonics, for instance v2.
First, we compute this new v1 versus transverse momentum and centrality for Au-Au collisions at RHIC using the hydrodynamic code NeXSPheRIO. Even without dedicated analysis of this new v1, indirect evidence has been obtained from recent STAR correlation data, and we compared our results with those inferred data, finding remarkable agreement. As the fluctuations in the initial geometry break the symmetry of the initial density profile, there will be one direction where the profile is steepest. This effect can be quantified bythe magnitude dipole asymmetry ε1, and by the steepest direction for a smooth profile Φ1. For smooth initial conditions, one expects Ψ1 = Φ1 and v1 ∝ ε1 in each event. We compute those features for our bumpy initial conditions and compare with the directed flow quantities. We find that the event plane of v1 is correlated with the angle of the initial dipole of the distribution, as predicted, though with a large dispersion, but it is uncorrelated with the reaction plane. This shows that the dipole asymmetry is indeed the mechanism to create v1. Reference: arXiv:1103.4605
123 / 124 Silicon Tracking for the Compressed Baryonic Matter Experiment at FAIR
Johann Heuser1
1 GSI Helmholtz Center for Heavy Ion Research GmbH, Darmstadt, Germany
The Compressed Baryonic Matter (CBM) experiment at the international Facility for Antiproton and Ion Research (FAIR) will conduct a comprehensive research programme on nuclear matter at high net baryonic densities. The fixed-target detector will record hadronic, leptonic and photonic observables from proton-nucleus and nucleus-nucleus collisions. Many of them are rare so that high collision rates up to 10 MHz will have to be mastered at minimum bias. The central component isa silicon tracking system for the trajectory and momentum determination of the hundreds of charged
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particles created in the collisions. Their efficient reconstruction is prerequisite for essentially allCBM observables. The tracker will comprise radiation hard silicon microstrip detectors and self-triggering readout electronics assembled into a large-area low-mass system. Progress with the design of the system, the assessment of its expected performance, and the realization of prototype components will be reported.
70 / 125 Directed flow and early thermalization
Iwona Wyskiel-Piekarska1 Piotr Bozek 1
1 Institute of Nuclear Physics PAN
For the first time, the generation of the directed flow of particles emitted from the fireball createdin heavy-ion collisions at RHIC is described using a 3+1D hydrodynamical model. The initial fireball density is constructed as a sum of contributions from forward and backward going participants. This asymmetry in the emission from the individual participants leads to a tilt of the source. Our model reproduces the experimentally observed negative directed flow in a wide range of central pseudorapidities andre- produces correctly the scaling of the directed flow when going from Au-Au to Cu-Cu systems [1]. We also propose to measure the thermalization time in the early stage of heavy-ion collisions using the directed flow of particles. We show that the directed flow is a very sensitive measure of the pressure equilibration in the first fm/c of the evolution. We demon- strate in hydrodynamic calculations that the directed flow is strongly reduced in the presence of even a very short pressure anisotropy. Our calculations show that the system must thermalize fast (<0.25fm/c). This suggests that the matter behaves as a strongly coupled system already atthefirst stages [2]. [1] P. Bozek and I. Wyskiel, Directed flow in ultrarelativistic heavy-ion collisions, Phys. Rev. C81 054902 (2010) [2] P. Bozek and I. Wyskiel-Piekarska, Indications of early thermalization in relativistic heavy-ion collisions, Phys. Rev. C 83 024910 (2011)
133 / 127 What is the surface tension of quark gluon bags?
Gennady Zinovjev1; Kyrylo Bugaiev1
1 Bogolyubov Inst. for Theor. Phys. (ITP), Kiev, Ukraine
We discuss the novel view at the colour confinement which, on the one hand, allows us to find out the surface tension coefficient of quark gluon bags and, under a plausible assumption, to determine the endpoint temperature of the QCD phase diagram, on the other hand. The developed model considers the confining colour tube as the cylindrical quark gluon bag with non-zero surface tension. A close inspection of the free energies of elongated cylindrical bag and the confining colour tube that connects the static quark-antiquark pair allows us to find out the string tension in terms of the surface tension, thermal pressure andthebag radius. Using the derived relation it is possible
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to estimate the bag surface tension at zero temperature directly from the lattice QCD data. The re- quirement of positive entropy density of such bags leads to negative values of the surface tension coefficient of quark gluon bags at the cross-over region, i.e.at the continuous transition to deconfined quarks and gluons. It is shown that such an approach naturally accounts for an existence of a very pronounced surpris- ing maximum of the string entropy observed in the lattice QCD simulations, which, as we argue, signals about the fractional surface formation of the confining tube. Also we analyze the vicinity of the (tri)critical endpoint of the QCD phasedia- gram and discuss the role of vanishing surface tension coefficient for the endpoint existence.
124 / 129 DENSE COLD MATTER STUDY WITH SPECIAL TRIGGER AT TWA, NUCLOTRON, NICA AND FAIR. Project Status.
Alexey Stavinskiy1
1 ITEP
New phase diagram sector at extrimely large baryon density and low temperature is proposed for the laboratory study at TWA(ITEP),Nuclotron-M,MPD-NICA(JINR), CBM@SIS100(FAIR). High pt central rapidity double cumulative trigger for this study is proposed and tested experimentally at ITEP ion accelerator by FLINT collaboration.FLINT experiment is dedicated to the research program of dense cold matter search and study. Experimental data of two runs (2007 and 2010) are presented. Photons spectra where measured in CBe interaction at 3.2GeV/nucleon within angular region 35°–70° (l.s.). It is shown, that the measured photon spectra are indicating the domination of flucton-flucton interaction. Results of two runs are consistent with each other. Proposed measurements programs for future facilities MPD-NICA and CBM-FAIR(SIS100) are discussed.
6 / 130 Enhancement of flow anisotropies due to magnetic field inrela- tivistic heavy-ion collisions
Saumia Pandiat1
Ajit Srivastava 2; Ranjita Mohapatra 2
1 Institute of Physics 2 Institute of Physics
It is known that the presence of background magnetic field in cosmic plasma distorts the acoustic peaks in CMBR. This primarily results from different types of wavesin the plasma with velocities depending on the angle between the magnetic field and the wave vector. We consider the conse- quences of these effects in relativistic heavy-ion collisions where very strong magnetic fields arise during early stages of the plasma evolution. We show that flow coefficients can be significantly af- fected by these effects when the magnetic field remains strong during early stages due tostrong induced fields in the conducting plasma. In particular, the presence of magnetic field canleadto enhancement in the elliptic flow coefficient v_2.
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Pre-equilibrium and initial state / 131
Initial state fluctuations at RHIC and LHC: hadronic or partonic origin?
Hannah Petersen1
Berndt Mueller 1; Steffen Bass 1
1 Duke University
This talk will discuss how triangular flow measurements in Pb+Pb collisions at the LHC can be used to constrain the origin of initial state fluctuations. We explore the energy dependence of elliptic and triangular flow within a (3+1)-dimensional hybrid framework starting from a non-equilibrium initial state with event-by-event fluctuations and including an ideal hydrodynamical expansion phase followed by hadronic Boltzmann transport. This approach has been shown to describe well the existing RHIC and LHC data on bulk observables such as particle yields, spectra and elliptic flow. The initial energy deposition canbe modeled either in a partonic or a hadronic picture using, respectively, a parton cascade or the hadronic transport model UrQMD. We present a detailed comparison between the shape and fluctuations of the two initial conditions prior to the hydrodynamical evolution. Our analysis then compares the differences in final state observables such as triangular flow inorderto identify sensitivities to the degrees of freedom driving the energy deposition.
132 Centrality dependence of observables in the core - corona model
Joerg Aichelin1
Constantin Schreiber 1; Klaus Werner 1
1 subatech
To understand the centrality dependence of the measured observables, like the multiplicity < pt > and the elliptic flow of identified particles at midrapidity as well as the elliptic flow ofcharges hadrons, has been a challenge for theory since many years. Although the multiplicity of different particles in central collisions corresponds exactly to the expectation for a completely thermalized source the centrality dependence is incompatible with this assumption. A while ago it has been realized that even in the most central collisions there remain particles (usually close to the surface of the interaction zone) which do not come to equilibrium (corona particles) whereas others come to a local equilibrium (core particles). Corona particles produce hadrons like pp collision. The relative fraction of corona particles can be calculated in the Glauber approach and increases with decreasing centrality? This variable core fraction is the origin of the centrality dependence of the observables. The approach has no free parameter and reproduces quantitatively the experimental results. Espe- cially it explains an observations which have been unexplained since quite a while: the enhancement of (multi) strange baryons and the fact that this enhancement becomes smaller at larger beam ener- gies. Recently this model has been extended to dynamical variables like the centrality dependence of < pt > and v2 of identified particles. The model reproduces quantitatively the centrality dependence of the elliptic flow of charged particles
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without any new parameter which has been considered so far as an observable which allows to fix the viscosity of a plasma. Our model shows that this centrality dependence can also be predicted assuming the same fraction of completely equilibrized core and not equilibrized corona particles which has been used to understand the centrality dependence of the multiplicity. In the presentation we will display the model and make comparisons with the EPOS event genera- tor which is based as well on the distinction between core and corona particles and describes the rapidity dependence of many observables. Then we demonstrate that the centrality dependence of all observables at midrapidity is well described in this approach, at SPS as at RHIC, and for CuCu as well as for AuAu. If data are available we will extend the model to LHC energies. The interpretation of the results in physical terms concludes the presentation.
134 / 133 The realistic QCD equation of state in relativistic heavy-ion colli- sions and the early Universe
Wojciech Florkowski1
1 Institute of nuclear Physics, Krakow
The realistic equation of state of strongly interacting matter [1,2], that has been successfully applied in the recent hydrodynamic studies of hadron production in relativistic heavy-ion collisions at RHIC [3,4], is used in the Friedmann equation to determine the precise time evolution of thermodynamic parameters in the early Universe [5]. A comparison with the results obtained with simple ideal- gas equations of state is made. The realistic equation of state describes a crossover rather than the first-order phase transition between the quark-gluon plasma and hadronic matter. The numerical calculations show that small inhomogeneities of strongly interacting matter in the early Universe are moderately damped during such crossover. The crossover character of the QCD transition indicates that there are small chances for observation of exotic phenomena connected with the first order phase transitions (quark nuggets, strangelets). Similarly, damping of the energy density perturbations suggests that no strong energy-density peaks are formed, that may lead to the formation of cold dark matter clumps discussed in earlier publica- tions. [1] Y. Aoki, Z. Fodor, S. D. Katz, K. K. Szabo, JHEP01, 2006, 089. [2] S. Borsanyi et al., JHEP09, 2010, 073. [3] M. Chojnacki, W. Florkowski, Acta Phys. Polon.B38, 2007, 3249. [4] W. Broniowski, M. Chojnacki, W. Florkowski, A. Kisiel, Phys.Rev.Lett.101, 2008, 022301. [5] W. Florkowski, Nucl.Phys.A853, 2011, 173.
135 / 136 Role of Finite Size Baryons in QCD Phase Transition and Critical Point
Prashant Kumar Srivastava1
C. P. Singh 1
1 Banaras Hindu University
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The physics regarding the existence of the critical point on the QCD phase boundary still remains unclear and its precise location is quite uncertain. We follow the suggestion of T. D. Lee et. al. [Phys. Rev. D9, 2291 (1974)] that a phase transition at high baryon density in a bulk matter can be realized in which nucleon loses part of its mass and thus baryons play a significant role in the phase transition. We suggest that the hadron gas consists of pointlike mesons and each baryon having a geometrical hard-core size. It means that mesons can fuse into one another while baryons experience a repulsive force with other baryons when densely packed. We formulate an excluded volume model existing for the equation of state (EOS) of hot, dense hadron gas and for the quark gluon plasma we use a thermodynamically consistent quasiparticle model (QPM). We construct a first order phase transition using Gibbs’ equilibrium criteria. This leads to an interesting and surprising finding that a critical point exists in such a formulation beyond which a cross-over region appears. We find that such a picture always appears in all excluded volume models considered in the literature. For ideal hadron gas model, there is no critical point in the diagram. In the mean field model also, we do not get a critical point unless we incorporate an excluded potential effect. Our analysis strongly suggests that the existence of a critical point and a cross-over region owes its explanation in the finite size baryons in the hadron gas. We find an interesting result that the ratio of the baryons to thetotal hadrons at the critical point is around 0.2 in all types of models and thus a cross-over region starts as soon as this ratio becomes smaller than 0.2.
Global and collective dynamics / 137
Far-from-equilibrium anisotropic collective flow
Nicolas Borghini1 Clément Gombeaud 1
1 University of Bielefeld
[email protected], [email protected]
Novel analytical results for the anisotropic collective flow of massive particles with a small interac- tion cross-section are presented. In particular, we show that, even when particles rescatter at most once, a sizable elliptic flow v2 is generated, with mass ordering of the various particle species.
136 / 138 Describing sQGP through the Friedberg-Lee model
Song Shu1 Jiarong Li 2
1 Faculty of Physics and Electronic Technology, Hubei University, China 2 Institute of Particle Physics, Hua-Zhong Normal University, China
The FL model is studied at finite temperature and density. The soliton solutions of the FL model in deconfinement phase transition are solved and thoroughly discussed for certain boundary conditions. We indicate that the solitons before and after the deconfinement have different physical meanings: the soliton before deconfinement represents hadron, while the soliton after the deconfinement represents the bound state of quarks which leads to a sQGP phase. The corresponding phase diagram is given.
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Jets / 140
Measurements of Jets and Jet Quenching in sqrt(s_NN)=2.76 TeV PbPb Collisions with the ATLAS Detector at the LHC
Toni Baroncelli1
1 Physics Department University of ROMA TRE - Rome -Italy
[email protected], [email protected]
Jet quenching, the parton energy loss in the hot and dense medium created in ultra-relativistic heavy ion collisions, is a well-established experimental phenomenon at RHIC. However, existing single hadron, di-hadron and multi-hadron measurements from RHIC do not provide a complete understanding of the experimental results and do not sufficiently constrain theoretical models. Re- constructed jet measurements in heavy ion collisions are expected to significantly improve exper- imental sensitivity to quenching and to more stringently constrain theoretical descriptions of the quark/gluon-medium interaction. Thus, prior to its commencement, it was anticipated that theLHC heavy ion program would substantially advance the study of jet quenching by providing access to jets with transverse energies in excess of 100 GeV – sufficiently high that the underlying event would provide only a modest perturbation to the jet measurements. Immediately following turn-on of the LHC in November, 2010, that expectation was satisfied through the observation of large di-jet asymmetries that may indicate substantial jet quenching. In this talk we will present results from ATLAS measurements√ of single jet production, di-jet correlations and jet fragmentation in Pb+Pb collisions at sNN = 2.76~TeV. These results include an update on the original di-jet asymmetry analysis using the full statistics from the Fall 2010 LHC Pb+Pb run.
Global and collective dynamics / 141
Measurement of elliptic flow in sqrt(s_NN)=2.76 TeV PbPb colli- sions with the ATLAS detector at the LHC.
Toni Baroncelli1
1 Physics Department University of ROMA TRE - Rome -Italy
[email protected], [email protected]
The measurement of the elliptic flow for charged particles in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV with the ATLAS detector will be presented in a wide range of pseudorapidity, transverse mo- mentum and collision centrality. The elliptic flow is measured by correlating azimuthal anglesof reconstructed particle tracks with the event plane angle obtained from forward calorimeters. A large pseudorapidity gap between the tracking system and forward calorimeters significantly re- duces contributions from short-range non-flow effects. For the first time at this energy, elliptic flow is measured over 5 units of pseudorapidity, from -2.5 to 2.5, and over a broad range in transverse momentum, 0.5-20 GeV. The results will be discussed in the context of previous measurements and theoretical model predictions.
Global and collective dynamics / 143
Measurement of charged particle pseudorapidity density in PbPb collisions at sqrt(s_NN) = 2.76 TeV with the ATLAS detector at the LHC
Toni Baroncelli1
32 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
1 Physics Department University of ROMA TRE - Rome -Italy
[email protected], [email protected]
Charged particle multiplicity is an important bulk observable for heavy ion collisions. It measures the global features of the medium produced and constrains the initial conditions of the system. It also provides an important test for dynamical model calculations which predict the dependence of multi- plicity on centrality at RHIC and the LHC. We present the study of charged particle pseudorapidity density distributions over a broad range of pseudorapidity and centrality in Pb+Pb collisions at √sNN = 2.76 TeV with the ATLAS detector at LHC. The centrality dependence of the particle density near mid-rapidity scaled by the number of participating nucleon pairs (dNch/dη(|η| < 0.5)/(0.5Npart)) is presented. Comparisons with results from previous measurements are used to study the collision en- ergy dependence. The pseudorapidity distributions measured over four units of pseudorapidity are compared with those of different collision systems and energies as well as dynamical models.
Jets / 144
Measurements of charged particle spectra in sqrt(s_NN)=2.76 PbPb collisions with the ATLAS detector at the LHC
Toni Baroncelli1
1 Physics Department University of ROMA TRE - Rome -Italy
[email protected], [email protected]
The measurement of charged particle spectra in heavy ion collisions is a direct way to studyproper- ties of hot and dense matter created in these interactions. The centrality dependence of the spectral shape is an important tool to understand the interplay between collective flow and energy loss mech- anisms. The ATLAS detector at the LHC took lead-lead data at 2.76 TeV per nucleon-nucleon pair with an integrated luminosity of just over 9µb-1. The ATLAS inner detector consists of 3 layers of silicon pixel detectors and 4 double sided strip layers in the barrel regions, with pixel and strip discs covering the forward region out to |η| = 2.5. Due to the excellent capabilities of the ATLAS detec- tor, and its stable operation during the first heavy ion run, these data allow measurements ofthe charged particle spectra and their ratios in different centrality bins over a wide range of transverse momenta and pseudorapidity. Comparison of ATLAS results to the results measured at lower energy will provide the opportunity to study the differences between the medium formed at the LHC and RHIC.
145 Study of Ultraperipheral processes in sqrt(s_NN)=2.76 Pb+Pb col- lisions with the ATLAS detector at the LHC
Toni Baroncelli1
1 Physics Department University of ROMA TRE - Rome -Italy
Besides the study of strongly-coupled matter, heavy ion collisions at the LHC provide opportuni- ties to study photon-nucleus and two-photon reactions in a hitherto unexplored energy regimse. Photoproduction of vector mesons off of the strong electromagnetic fields generated by the highly Lorentz-contracted nuclei provides a tool to study the interactions of quark-antiquark dipoles with strong gluon fields. This talk presents a first study of these large impact parameter “ultraperipheral” collisions (UPC), with a data set corresponding to up to 9 µb-1 of lead-lead collisions at a nucleon- nucleon center-of-mass energy of 2.76 GeV, recorded by the ATLAS Detector at the LHC. Two-prong
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events are selected with essentially no other activity registered in the rest of the detector, except for forward neutrons measured by the ATLAS zero degree calorimeters. Results on di-muon decays into J/psi and other channels will be presented.
7 / 146 Measurement of higher-order flow harmonics in sqrt(s_NN)=2.76 TeV Pb+Pb collisions with the ATLAS detector at the LHC
Soumya Mohapatra1
1 Department of Physics-State University of New York (SUNY)
Collective harmonic flow and jet-medium interactions are two phenomena under intense studyin ultra-relativistic heavy ion collisions at RHIC and the LHC. One outstanding question is how to dis- entangle these two contributions for various single and multiple particle observables. Both higher- order harmonic flow (v1, v2, v3, …) and jet-medium interactions, for example, have been argued to be responsible for several novel structures observed in two-particle ∆η and ∆ϕ correlations. In this poster, we present ATLAS measurement of two particle correlation in a broad momentum and cen- trality range. We carry out a Fourier analysis of the correlation function and extract the individual flow harmonics. We compare the first six terms(v1-v6) with those measured independently from an event plane method. We discuss the impact of these results for disentangling harmonic flow and jet-medium effect, and for understanding the nature of transition from the flow-dominated low pT region to the jet-dominated high pT region.
12 / 147 Measurements of Jet Production and Jet Fragmentation in sqrt(s_NN) = 2.76 TeV Pb+Pb Collisions with the ATLAS detector at the LHC
Toni Baroncelli1
1 Physics Department University of ROMA TRE - Rome -Italy
[email protected], [email protected]
The LHC has opened a new kinematic regime for the jet measurements in heavy ion collisions. With the factor of 14 increase in collision energy compared to RHIC data, new insights have already been achieved. The observation of centrality-dependent di-jet asymmetry measured by ATLAS andCMS is strongly suggestive of jet quenching – strong energy loss of parton traversing a hot and dense QCD matter. In this poster we will concentrate on details of single-jet and di-jet measurements in ATLAS, in particular on jet energy resolution and background fluctuations. We will also present results on jet fragmentation.
Jets / 149
Jet quenching from RHIC to LHC
Thorsten Renk1
1 University of Jyväskylä
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Despite a wealth of experimental data for high p_T processes in heavy-ion collisions, discriminating between different models of hard parton-medium interactions has been difficult. A large reasonis that the pQCD parton spectrum at RHIC is so steeply falling that distinguishing even a moderate shift in parton energy from complete parton absorption is essentially impossible. In essence, energy loss models are effectively only probed in the vicinity of zero energy loss and as a result, onlythe pathlength dependence of energy loss offers some discriminating power at RHIC kinematics. At LHC, this is no longer the case: Due to the much flatter shape of the parton spectra originating from 2.76 AGeV collisions, the available data probe much deeper into the model dynamics. A simultane- ous fit of the nuclear suppression both at RHIC and LHC kinematics has thus a huge potentialto discriminate between various models with equally good description of RHIC data alone.
71 / 151 Effects of parton radiative processes on Quark-Gluon Plasma ther- malization
Bin Zhang1 Warner Wortman 1
1 Arkansas State University
Radiative processes and dynamical screening are important for a precise description of the dynamics of relativistic heavy ion collisions. When evolutions from inside-outside and thermal initial condi- tions are compared, the parton system produced in relativistic heavy ion collisions is found to be able to overcome expansion and move toward thermalization via parton collisions. Scaling behav- iors show up in both the pressure anisotropy and the energy density evolutions. In particular, the pressure anisotropy evolution shows an approximate coupling constant scaling when radiative pro- cesses are included. It approaches an asymptotic time evolution on a time scale of 1 to 2 fm/c. The energy density evolution approaches an asymptotic time evolution that decreases slower than the ideal hydro evolution. These observations indicate that partial thermalization can be achieved and viscosity is important for the evolution during the early longitudinal expansion phase of a relativistic heavy ion collision. Radiative processes are the driving force behind gluon chemical equilibration. The effects of these processes, or of chemical equilibration, on kinetic equilibration can be studied by comparing the evolution with only the elastic process to that including radiative processes. When the initial condi- tion is close to chemical equilibrium, the opening up of the inelastic channels leads to more kinetic equilibration. If the initial condition is highly undersaturated, the additional production of particles quickly leads to smaller cross sections that counteract the increase in the particle number. Then kinetic equilibration is less sensitive to whether there are radiative processes. On the other hand, kinetic equilibration also affects chemical equilibration. As expected, when there are only elastic processes, the system goes farther and farther away from chemical equilibrium. It is interesting to see that systems with the same initial fugacity but different initial pressure anisotropies have different early fugacity evolutions. In addition to the interplay between chemical equilibration and kinetic equilibration, the pressure anisotropy difference evolution for systems starting from different initial pressure anisotropies is studied to gain better insight into the approach to the asymptotic evolution. The difference evolution is found to follow an exponential proper time dependence after a short period of time. In the case that includes radiative processes, the larger the coupling constant or the larger the initial energy density, the faster the difference decreases. The evolution curves for different coupling constants and initial energy densities appear to come from the same point. Pressure anisotropy evolutions from thermal initial conditions and Color Glass Condensate motivated initial conditions are compared to study the effects of initial particle momentum distribution. Radiative processes are again shown to makeabig difference in system evolution. When only the gluon elastic process is included, kinetic equilibration
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is sensitive to the initial momentum distribution. If radiative processes are included, the pressure anisotropy evolution is robust against changes in the initial momentum distribution. Reference: Parton radiative processes and pressure isotropization in relativistic heavy ion collisions, Bin Zhang, Warner A. Wortman, Phys. Lett. B 693, 24 (2010).
Theory developments / 153
Some new results on high-energy ”jet stopping” in AdS/CFT
Peter Arnold1 Diana Vaman 1
1 University of Virginia
A very basic theoretical question is: How far does a high-energy excitation travel in a quark-gluon plasma, and how does that distance scale with energy? In weak coupling, the stopping distance scales with energy as E^(1/2), up to logarithms. In strongly-coupled plasmas with gravity duals, theorists have found that the maximum stopping distance scales instead like E^(1/3). In the latter case, we show that there can be an important distinction between typical and maximum stopping distances. For the strongly-coupled excitations we study, we find that the typical stopping distance scales as E^(1/4).
Theory developments / 154
Running coupling corrections to high energy inclusive gluon pro- duction
William Horowitz1; Yuri Kovchegov2
1 University of Cape Town 2 The Ohio State University
We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. In thefinal answer for the cross section the three powers of fixed coupling are replaced by seven factors of running coupling, five in the numerator and two in the denominator, forming a ‘septumvirate’ of running couplings, analogous to the ‘triumvirate’ of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling kT-factorization formula for gluon produc- tion which includes non-linear small-x evolution. This work is the latest theoretical improvement on the approach used recently by Albacete and Dumitru in arXiv:1011.5161 [hep-ph] to accurately predict the centrality dependence of the charged particle multiplicity density measured by ALICE collaboration.
156 Characterizing quark gluon plasma by Heavy Flavors
36 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
santosh K das1 Jan-e Alam 1
1 Variable Energy Cyclotron Centre
The drag and diffusion coefficients of charm and bottom quarks propagating through quark gluon plasma (QGP) have been evaluated for conditions relevant to nuclear collisions at Large Hadron Collider (LHC) and at Relativistic Heavy Ion Collision (RHIC). The dead cone and Landau-Pomeronchuk-Migdal (LPM) effects on radiative energy loss of heavy quarks have been considered. Both radiative and collisional processes of energy loss are included in the {\it effective} drag and diffusion coefficients. With these effective transport coefficients we solve the Fokker Plank (FP) equation for the heavy quarks executing Brownian motion in the QGP. The solution of the FP equation has been used to evaluate the nuclear suppression factor, RAA and elliptic flow v2 for the non-photonic single electron spectra resulting from the semi-leptonic decays of hadrons containing charm and bottom quarks. It is observed that the experimental data from RHIC on RAA and v2 of nonphotonic electrons can be reproduced simultaneously within the pQCD framework for the same set of input. The RAA and v2 of the non-photonic electron from heavy meson decays produced in nuclear collisions at LHC and low energy RHIC run have also been predicted.The effects of mass on RAA has also been highlighted.
41 / 157 Heavy quarkonia in a quark-gluon plasma: coupled evolution and dynamics
Nicolas Borghini1 Clément Gombeaud 1
1 University of Bielefeld
[email protected], [email protected]
We consider the possibility that heavy quarkonia admit different bound states in a QGP, between which they can transition dynamically. We show that the vacuum mass eigenstates are not the relevant eigenstates for the in-medium dynamics. This leads in particular to abundance ratios ofthe various states which deviate from the predictions of static models. Additionally, the quarkonium dynamics differ from that of states with a definite mass.
137 / 158 Study of the expansion and the phase transition of a quark plasma to an hadron phase with the NJL model using a new QMD ap- proach.
Rudy Marty1 Joerg Aichelin 1
37 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
1 Subatech
One of the challenges of present day in nuclear physics is the understanding of the phase transition between the quark gluon plasma and the hadronic world. We can divide space into cells to create a lattice of partons, or describe the transformation of energy via the Cooper-Frye formula, butin these cases we miss some dynamical aspects. That is why I will present a study of the expansion and the phase transition with aQCDinspired model : the Nambu-Jona-Lasinio (NJL) model. This model is particularly useful to describe quark matter at low temperature (below Λ_QCD). It provides an effective mass at finite (T,μ), andthen cross sections and decay widths for hadrons (possible mixed phase). Recent results are presented using these data within a Quantum Molecular Dynamics (QMD) code. This code is designed for local interactions at finite (T,μ). It is a fully relativistic codewhichis Lorentz invariant and avoids the No Interaction Theorem in a different way than previous similar attempts. Finally we know that there are correlations inside the plasma before the phase transition. We discuss how this scenario can be modeled with these tools to understand this transition in detail and to find observables which distinguish between the different approaches.
QCD Phase diagram / 159
QCD thermodynamics at intermediate coupling
Jens Andersen1; Lars Leganger1; Michael Strickland2; Nan Su3
1 Norwegian University of Science and Technology 2 Gettysburg College 3 Bielefeld University
The weak-coupling expansion of the QCD free energy is known to order g^6*log[g], however, the resulting series is poorly convergent at phenomenologically relevant temperatures. I will discuss how the gauge invariant hard-thermal-loop perturbation theory (HTLpt) reorganization of the cal- culation improves the convergence of the successive approximations to the QCD free energy. I will present new results of an HTLpt calculation of QCD thermodynamics to three loops. The results of this calculation are consistent with lattice data down to 2-3T_c. This is a non-trivial result since,in this temperature regime, the QCD coupling constant is neither infinitesimally weak nor infinitely strong with g~2, or equivalently alpha_s~0.3. Therefore, we have a crucial test of the quasiparticle picture in the intermediate coupling regime. Our results suggest that HTLpt provides a systematic framework that can be used to calculate static and dynamic quantities for temperatures relevant at LHC.
QCD Phase diagram / 161
Moments of charge fluctuations, pseudo-critical temperatures and freeze-out in heavy ion collisions
Frithjof Karsch1
1 Brookhaven National Laboratory
38 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
In the chiral limit and at temperatures close to the QCD phase transition temperature physical ob- servables are expected to show universal properties that are controlled by the symmetry class of a 3-dimensional O(4) spin model [1]. Higher moments of net baryon number as well as electric charge fluctuations are sensitive to these universal features of the chiral phase transition [2].
The sixth order moments are the first moments which will diverge in the chiral limit attheQCD phase transition temperature. At non-zero values of the light quark masses the sixth order moment of baryon number fluctuations has a pronounced minimum at a pseudo-critical temperature which is close to the temperature where fluctuations of the chiral order parameter are the largest.
We present a calculation of the O(4) scaling functions that control scaling properties of the net baryon number fluctuations [3]. Using these universal scaling functions as well as PNJL model calculations [4] we show that the sixth order moment of baryon number fluctuations is negative in the vicinity of the pseudo-critical temperature for the chiral transition and present new results from lattice calcula- tions using the highly improved staggered fermion action (hisq). These QCD results are in striking contrast to hadron resonance gas model calculations. We conjecture that higher order moments of net baryon number and electric charge fluctuations are well suited to characterize freeze-out con- ditions in heavy ion collisions. Their experimental analysis in low-energy runs at RHIC as well as at LHC will allow to verify to what extent freeze-out occurs from a thermal medium close to criticality. [1] O. Kaczmarek et al., Phase boundary for the chiral transition in (2+1) -flavor QCD at small values of the chemical potential Phys. Rev. D83, 014504 (2011). [2] F. Karsch and K. Redlich, Probing freeze-out conditions in heavy ion collisions with moments of charge fluctuations, Phys. Lett. B695, 136 (2011). [3] J. Engels and F. Karsch, The scaling functions of the free energy density and its derivatives for the 3d O(4) model, in preparation. [4] J. Engels, B. Friman, F. Karsch, K. Redlich and V. Skokov, Fluctuations as probe of the QCD phase transition and freeze-out in heavy ion collisions at LHC and RHIC, arXiv:1103.3511.
164
Photon and dilepton production from viscous QGP
Asis Chaudhuri1
Bikash Sinha 1
1 Variable Energy Cyclotron Centre
Photons and dileptons are important probe for the lattice QCD predicted deconfined matter, com- monly called Quark-Gluon-Plasma (QGP). Unlike the strongly interacting hadrons, which can give information about the ‘last scattering surface’, electromagnetically interacting photons and dilep- tons give information about the matter at the deep interior. Viscous effects on photon and dilepton production is studied recently [1,2]. However, the model [1,2] appears to have some inconsistency that viscous effects on fluid evolution were not accounted for. In a recent work, we haveremoved the inconsistency [3]. Photon production rate from Compton and annihilation processes was convo- luted over the space-time evolution of the QGP, obtained by explicitly solving Israel-Stewart’s 2nd order theory of hydrodynamics. In viscous dynamics, photon/dilepton production is modified due to (i) changed space-time evolution of the fluid and (ii) non-equilibrium correction to the equilibrium distribution function. The non-equilibrium correction grows with viscosity as well with transverse momentum. Applicability of viscous hydrodynamics requires that the non-equilibrium correction is small. Viscous effects on photon and dilepton production are strong [3,4]. Even for AdS/CFT lower bound of viscosity (η/s=0.08), strong viscous correction render the hydrodynamics inapplicable be- yond pT ~ 1.5 GeV. If QGP viscosity is larger than the Ads/CFT limit, then limitation will be even more severe. Photon production as a function of initial time, also suggest that if the inverse slope parameter of the photon spectra, is measured within an accuracy of ~20-80 MeV, one can possibly
39 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
estimate the initial time and viscosity within reasonable limit. We also find that for dilepton invari- ant mass M~600-900 MeV, the dilepton to photon ratio is sensitive to viscosity to entropy ratio of the medium. The dilepton to photon ratio can possibly serve as a ‘viscometer’ forQGP. [1] K. Dusling, Nucl.Phys.A839(2010)70. [2]K. Dusling and S. Lin, Nucl.Phys A809(2008)246. [3] A. K. Chaudhuri and B. Sinha, Phys. Rev. C83(2011)039405. [4] A. K. Chaudhuri and B. Sinha, to be published.
165 Hydrodynamical analysis of centrality dependence of charged par- ticle’s multiplicity in √sNN=2.76 TeV Pb+Pb collision
Asis Chaudhuri1
Victor Roy 1
1 Variable Energy Cyclotron Centre
Ongoing heavy ion collision at Large Hadron Collider, CERN is expected to settle the important issues like the possibility of formation of the lattice QCD predicted strongly interacting nuclear mat- ter known as Quark Gluon Plasma (QGP) and the important issue of thermalization and thetime taken by the system to achieve the same. Recently ALICE collaboration [1] measured the centrality dependence of charged particle multiplicity in √sNN=2.76 TeV Pb-Pb collision. The viscous hydro was pretty successful to describe the experimental particle multiplicity and elliptic flow data atRHIC energy, from which the initial condition of the produced medium can also be traced back. We use 2+1D viscous hydrodynamic model to explain the centrality dependence of experimental charged particle multiplicity produced in Pb-Pb √sNN=2.76 TeV collision and obtain the initial condition of the fluid produced. The space time evolution of the fluid is obtained by solving energy momen- tum conservation along with solving relaxation equation for shear viscous stresses obtained from Israel-Stewart’s 2nd order theory. The conservation equation were closed with an equation of state (EOS) constructed from recent lattice data [2] for QGP phase which undergoes a crossover transi- tion to Hadronic phase (comprising all the resonances below mass 2.5 GeV) at crossover temperature Tco=174 MeV. It was assumed that initial energy density was mostly scaled with number of binary collision and the system freezes out when the temperature at any space-time points reaches Tf=130 MeV. Our study [3] shows that hydrodynamical evolution of QGP fluid, with viscosity to entropy density ratio η/s=1/4π, initialized to central energy density εi =370 GeV/fm3 at initial time τi=0.6 fm/c or initialized to energy density εi =72 GeV/fm3 at initial time τi=1.0 fm/c explains the ALICE data on centrality dependence of charged particle multiplicity. Smaller initial time τi=0.2 fm/c do not re- produce the data. Initial time τi=0.6-1.0 fm/c is also consistent with ALICE measurement of charged particles pT spectra and elliptic flow. We also show that an alternative of hadronic resonance gas, even at the unphysical high temperature of T=220 MeV do not explains the ALICE data. [1] K Aamodt et al. [The ALICE collaboration], arXiv : 1011.3916 [2] S. Borsanyi et al. JHEP 1011, 077 (2010),[arXiv : 1007.2580[hep-lat]]. [3] A.K.Chaudhuri and Victor Roy, arXiv: 1102.4936 [nucl-th].
138 / 166 Entanglement between deconfinement transition and chiral sym- metry restoration
Yuji Sakai1
Hiroaki Kouno 2; Masanobu Yahiro 1; Takahiro Sasaki 1
40 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
1 Kyushu University 2 Saga University
We extend the Polyakov-loop extended Nambu–-Jona-Lasinio (PNJL) model by introducing an effec- tive four-quark vertex depending on Polyakov loop. The effective vertex generates entanglement interactions between Polyakov loop and chiral condensate. The new model is consistent with lattice QCD data at imaginary quark number chemical potential and real and imaginary isospin chemical potentials, particularly on strong corre- lation between the chiral and deconfinement transitions and also on the quark mass dependence of the order of the Roberge-Weiss endpoint. We investigate the influence of the entanglement interac- tions on the location of the tricritical point at real isospin chemical potential and on the location of the critical endpoint at real quark number chemical potential.
13 / 168
Probing nuclear parton densities and parton energy loss processes through photon + heavy-quark jet production in p-A and A-A col- lisions
Tzvetalina Stavreva1
Francois Arleo 2; Ingo Schienbein 1
1 LPSC 2 LAPTH
We present a detailed phenomenological study of the associated production of a prompt photon and a heavy quark jet (charm or bottom) in proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions. The dominant contribution to the cross-section comes from the gluon–heavy-quark (gQ) initiated subprocess, making this process very sensitive to the gluon and the heavy-quark nuclear parton densities. We show that the future p-A data to be collected at the LHC should allow one to disentangle the various nPDF sets currently available. In heavy-ion colli- sions, the photon transverse momentum can be used to gauge the initial energy of the massive parton which is expected to propagate through the dense QCD medium produced in those collisions. The two-particle final state provides a range of observables (jet asymmetry, photon-jet pair momentum, among others), through the use of which a better understanding of parton energy loss processes in the massive quark sector can be achieved, as shown by the present phenomenological analysis carried out in Pb-Pb collisions at the LHC.
169
Exotic Matter-Antimatter Molecules
Cheuk-Yin Wong1
Teck-Ghee Lee 2
1 Oak Ridge National Laboratory 2 Auburn University
41 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
In a nuclear collision at RHIC and LHC, a large number of particles and antiparticles are produced. The production of matter and antimatter particles in close space-time proximity raises the interesting question whether chance encounters of some of the produced charged particles and antiparticles may lead to the formation of exotic matter-antimatter molecules as debris of the collision. The detection of new matter-antimatter molecules may be a difficult task. It is nonetheless an interesting theoretical question to investigate the general factors affecting the stability of matter-antimatter molecules. Using a formalism similar to the previous investigation of the X(3872) as a heavy-quark molecular state [1], we find that matter-antimatter molecules with charged constituents (m1+,m2-,m2bar+,m1bar-) possess bound states if their constituent mass ratio m1/m2 is greater than about 4 [2]. This stability condition suggests that the binding of matter-antimatter molecules is a rather common phenomenon. We evaluate the binding energies of exotic matter-antimatter molecules (mu+ e-)-(e+ mu-), (pi+ e-)-(e+ pi-), (K+ e-)-(e+ K-), (p e-)-(e+ pbar), (p mu)-(mu+ pbar), and (K+ mu-)-(mu+ K-), which satisfy the stability condition. We estimate the molecular annihilation lifetimes in their s states. [1] C. Y. Wong, Phys. Rev. C69, 055202 (2004). [2] C. Y. Wong and T. G. Lee, arXiv:1103.5774 (2011).
139 / 170
Energy Dependence of the Identified Hadron Elliptic Flow and QCD Phase Structure
KeJun Wu1
Feng Liu 1; nu xu 2
1 1. Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079, China 2. The Key Laboratory of Quark and Lepton Physics (Huazhong Normal University) Ministry of Education, Wuhan, 430079, China 2 1. Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079, China 2. The Key Laboratory of Quark and Lepton Physics (Huazhong Normal University) Ministry of Education, Wuhan, 430079, China 3. Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
One of the most exciting goals for the field of the high-energy nuclear collisions is to understand the phase structure of matter with partonic degrees of freedom and the transition from partonic phase to hadronic phase. In this talk, we will utilize the elliptic flow (v2) as a tool to address phase boundary issue. The v2 reflects the early collision dynamics [1]. Using transport models AMPT[2] and UrQMD [3], we study the energy dependence of the identified hadron elliptic flow in Au+Au collisions. While in high-energy collisions where hadrons are formed dominantly via the process of parton coalescence, we find the observed number of quark scaling in v2 [1] for all hadrons,the violation of the scaling is evident for collisions at lower energies where the hadronic interactions become dominant. Due to the high baryon density, the violation is particularly strong for the case of proton and anti-proton. In this talk we will discuss the boundaries of the region of beam en- ergy, above which partonic interactions clearly dominate and below which hadronic interactions dominate. Other thermodynamic parameters, extracted around the energy region, like freeze-out temperature and baryonic chemical potential will also be discussed. References: [1] J. Adams et al. (STAR Collaboration), Nucl. Phys. A757, 102(2005) and references therein.
42 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
[2] Z.W. Lin et al., Phys. Rev. C72, 064901(2005). [3] S. A. Bass et al., Prog. Part. Nucl. Phys. 41, 255(1998).
Heavy flavors / 172
Quarkonium production at the LHC: QCD corrections and new observables
Jean-Philippe Lansberg1
1 IPNO, Université Paris-Sud 11
I will discuss the impact of QCD corrections on the P_T differential cross section for quarkonium production in pp collisions at RHIC, Tevatron and LHC energies, as well as the contributions from charm-gluon fusion. I will present comparisons between the predictions of the Color Singlet Model up to alpha_s^5 with the first LHC data both for J/psi and Upsilon. I will also show predictions for the polarisation to be compared with the forthcoming LHC results. Finally, I will motivate the introduction of new observables meant to better discriminate between the different mechanisms at work in quarkonium production at the LHC.
Jets / 173
Jets, mach cone, hot spots, ridges, harmonic flow, dihadron and γ-hadron correlations in high-energy heavy-ion collisions
Guo-Liang Ma1; Xin-Nian Wang2
1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China 2 Nuclear Science Division MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, California 94720
Within the AMPT Monte Carlo model, fluctuations in the initial transverse parton density are shown to lead to harmonic flows. The net back-to-back dihadron azimuthal correlation after subtraction of contributions from harmonic flows still has a double peak that is independent of the initial geo- metric triangularity and unique to the jet-induced Mach cone and expanding hot spots distorted by radial flow. The longitudinal structure of hot spots also leads to a near-side ridge indihadron correlation with a large rapidity gap. By successively randomizing the azimuthal angle of the trans- verse momenta and positions of initial partons, one can isolate the effects of jet-induced medium excitation and expanding hot spots on the dihadron azimuthal correlation. The double peaks in the net dihadron and γ-hadron correlation are quantitatively different since the later is caused only by jet-induced Mach cone. Reference: [1] Guo-Liang Ma and Xin-Nian Wang, arXiv:1011.5249
72 / 174 Kadanoff-Baym Approach to Thermalization of Gluonic Matter
43 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Akihiro Nishiyama1
1 University of Tsukuba
In this presentation, we propose the Kadanoff-Baym approach to the early nonequilibrium stage of ultrarelativistic heavy ion collisions and present recent results about equilibration of gluons. First we introduce the Kadanoff-Baym equation and present the proof of H-theorem for given off-shell dynamics of gluons. Next we show entropy production and equilibration with numerical analyses of this equation. Here we have adopted off-shell g ↔ gg effects as scattering processes which are prohibited in normal quasiparticle approximation. Finally we estimate the equilibration time (~1fm/c) of gluons for the coupling strength g2 = 1.0 and show the significance of off-shell effects in heavy ion collisions at RHIC and LHC energies.
58 / 175 Charged-hadron pseudorapidity distributions in the RDM at LHC energies
Georg Wolschin1
1 Heidelberg University
The energy dependence of charged-hadron production in relativistic heavy-ion collisions isinvesti- gated in a nonequilibrium-statistical relativistic diffusion model (RDM) with three sources [1]. Theo- retical pseudorapidity distributions are compared with PHOBOS AuAu data [2] at RHIC energies of sqrt(s_NN) = 0.13 and 0.2 TeV including the centrality dependence, and computed for PbPb central collisions at LHC energies of 2.76 and 5.52 TeV. Whereas the quark-gluon fragmentation sources are most important at RHIC energies, the nearly equilibrated source near midrapidity that arises from gluon-gluon collisions becomes the major ori- gin of particle production at LHC energies. This is confirmed in a comparison with recent ALICE data on charged-hadron pseudorapidity distributions in 2.76 TeV PbPb [3]. The midrapidity dip is determined by the interplay of the three sources [4]. [1] G. Wolschin, Prog. Part. Nucl. Phys. 59 (2007) 37. [2] B. Alver et al. (PHOBOS Collaboration), Phys.Rev.C 83 (2011) 02491. [3] K. Aamodt et al. (ALICE Collaboration), Phys. Rev. Lett. 105 (2010) 25230; Phys. Rev. Lett. 106 (2011) 032301. [4] G. Wolschin, arXiv:1102.3388 (2011); Phys. Lett. B, in press.
Jets / 176
Suppression of high p_T hadrons in PbPb Collisions at LHC
Xin-Nian Wang1 Enke Wang 2; Hanzhong Zhang 2; Tetsufumi Hirano 3; Xiao-fang Chen 2
1 IOPP / LBNL 2 IOPP
44 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
3 Tokyo University
[email protected], [email protected]
Nuclear modification√ factor RAA(pT ) for large transverse momentum pion spectra in P b + P b collisions at s = 2.76 TeV is predicted within the NLO perturbative QCD parton model. Effect of jet quenching is incorporated through medium modified fragmentation functions within the higher- twist approach. The jet transport parameter that controls medium modification is proportional to the initial parton density and the coefficient is fixed by the RHIC data on suppression oflarge pT hadron spectra. Data on charged hadron multiplicity dNch/dη = 1584 ± 80 in central P b + P b collisions from the ALICE Experiment at the LHC are used to constrain the initial parton density both for determining the jet transport parameter and the 3+1D ideal hydrodynamic evolution of the bulk matter that is employed for the calculation of RP bP b(pT ) for neutral pions
83 / 178
A few new experimental results on particle correlations
Stefania Velica1
1 Faculty of Physics, University of Bucharest
The study of the correlations among the particles emitted from the overlapping region ofthecol- liding nuclei gives the information about the conditions in the early stage of the collision and the system evolution. The analysis of correlations and fluctuations in the relativistic nuclear collisions addresses fundamental aspects of the quantum chromodynamics (QCD) and, therefore, to the prop- erties of strongly-interacting matter at extreme density and temperature. In this work we present the study of correlations between physical quantities describing the be- haviour of different charged particle types providing information on the formation of a newphase of the highly excited and dense nuclear matter. In this analysis were used the experimental results obtained in Au-Au and proton-proton collisions at with the BRAHMS experiment at RHIC. Using the usual methods from statistics and probability theory, we introduce a linear correlation coefficient for the longitudinal and transverse momentum components and for rapidity and transverse momentum for all charged particles ( , , and ) produced and detected with the BRAHMS experiment. For proving the existence of anomalous states in nuclear matter, unusual correlations between the longitudinal and transverse momenta should be observed in the rapidity range -0.1 < y < 3.5. It is, also, proposed that the change in pT spectra at high rapidities could be one of the possible signals of QGP forma- tion. These results are compared with others obtained in a large energy range, from the JINRDubna Synchrophasotron, up to CERN SPS, for symmetric and asymmetric collisions. Interesting anomal states of the nuclear matter can be observed.
8 / 179
V1 flow componet at LHC
Laszlo Pal Csernai1
D.D. Strottman 2; H. Stoecker 3; V.K. Magas 4
1 University of Bergen 2 Frankfurt Institute for Advanced Studies 3 Univ. of Frankfurt 4 Univ. of Barcelona
45 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Substantial collective flow is observed in collisions between Lead nuclei at LHC as evidenced bythe azimuthal correlations in the transverse momentum distributions of the produced particles. We perform simulations [1] of the Pb+Pb heavy ion collisions at LHC at 1.38 + 1.38 TeV/nucl within the three module model. The initial stages of the reaction, before the thermal equilibrium is reached, are simulated in terms of effective string rope model [2], based on longitudinally expanding strings of the color-magnetic field. The produced initial state is tilted, and, thus, the direction of thelargest pressure gradient is pointing in the “anti-flow” direction, what resulted in anti-flow peaks insimu- lations for RHIC and SPS [3]. However, one should not forget that this initial state also has a flow velocity distribution, which tends to further rotate it, and, thus, the direction of the strongest pres- sure gradient will change with time. The intermediate stages of the reaction are simulated witha (3+1)-dimensional fluid dynamical model, using the Particle in Cell (PIC) method adapted toultra- relativistic heavy ion collisions. The matter expands until it reaches freeze-out, which is treatedin the third module of our model. The resulting elliptic flow, v2, is in reasonable agreement with the data [4]. Furthermore, ourcal- culations also indicate that the v1-flow, which was rather weak at RHIC and SPS, and peakedat negative rapidities (named as 3rd flow component or anti-flow), now at LHC is expected topeak at forward rapidities (at the same side and direction as the projectile residue), and it may become stronger [1]. Thus, v1-flow provides a sensitive barometer to estimate the pressure and transport properties of the Quark-Gluon Plasma. In order to better study the transverse momentum flow dependence we suggest a new “symmetrized v1s” flow component, and make predictions for it. [1] L.P. Csernai, V.K. Magas, H. Stocker, D.D. Strottman, arXiv:1101.3451 [nucl-th]. [2] V.K. Magas, L.P. Csernai, and D.D. Strottman, Phys. Rev. C 64 (2001) 014901; Nucl. Phys. A712 (2002) 167. [3] L.P. Csernai, D. Rohrich, Phys. Lett. B 458 (1999) 454; B. Bauchle et al., J. Phys. G 34 (2007) s1077. [4] K. Aamodt et al. [The ALICE Collaboration], Phys. Rev. Lett. 105 (2010) 252302.
Jets / 181
Can we see from jet quenching that quark-gluon plasma becomes more perturbative at LHC than at RHIC
Bronislav Zakharov1
1 Landau Institute
We study the nuclear modification factor R_AA at RHIC and LHC energies. We account forthe radiative and collisional energy losses. Both the contributions are calculated with running \alpha_s accounting for fluctuations of the jet path lengths. The effect of the thermal suppression of\alpha_s is investigated. Comparison of the theoretical results with the experimental data obtained at RHIC and in the ALICE experiment at LHC demonstrates that the experimental R_AA may be described in pQCD with the entropy extracted from the multiplicity data. However for LHC the thermal sup- pression of \alpha_s should be stronger. This fact demonstrates that at LHC the quark-gluon plasma becomes more perturbative.
95 / 182 Dilepton interferometry: a tool to characterize different phases of matter produced in heavyion collisions
46 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
payal mohnaty1
Bedangadas Mohanty 2; Jane Alam 1
1 Variable Energy Cyclotron Centre 2 Variable Energy Cyclotron centre
The Hanbury-Brown-Twiss (HBT) radii from the correlation functions of the two virtual photons produced in the collisions of two nuclei at ultra-relativistic energies have been evaluated. We show that a study of the mass dependence of various interferometry radii extracted from the correlation functions of virtual photons can be a powerful tool to characterize and distinguish the hadronic and the partonic phases. It is shown that the non-monotonic variation of the HBT radii with invariant mass provides an access to the development of collective flow in the system. The sensitivity of the results on the initial thermalization time is also examined.
183
Charged Particle’s elliptic flow in 2+1D viscous hydrodynamics at LHC (√s=2.76 TeV) Energy in Pb+Pb collision. and QGP viscos- ity
Asis Chaudhuri1
Victor Roy 1
1 Variable Energy Cyclotron Centre
The azimuthal correlation of produced particles in the reaction plane or elliptic flow inheavyion collision is a sensitive probe to (i) degree of thermalization (ii) transport coefficient and (iii) the equa- tion of state (EoS) of the medium. Recently, ALICE collaboration measured (differential) elliptic flow in √s=2.76 TeV Pb-Pb collision [1]. We have analyzed the elliptic flow data to obtain an estimate of viscosity to entropy ratio η/s at LHC energy. Details can be found in [2]. In Israel-Stewart’s second order theory of hydrodynamics, we have simulated elliptic flow in 2.76 TeV Pb+Pb collisions. We have assumed that initial Pb+Pb collisions produces a QGP fluid which thermalizes in the time scale, τi=0.6 fm/c. Hydrodynamical evolution of the fluid is governed by a lattice motivated equation of state with confinement-deconfinement cross-over tran- sition at Tc=174 MeV. The initial condition of the fluid was fixed to reproduce ALICE measurements for charged particles multiplicity in 0-5% collisions. Ideal QGP fluid require rather large initial en- ergy density, ei=90 GeV/fm^3. Initial energy density is reduced if the fluid is viscous, e.g. ei =78, 70, 60 GeV/fm^3 for viscosity to entropy ratio η/s=0.08, 0.12 and 0.16 respectively. ALICE data for charged particles elliptic flow in 20-30%, 30-40% and 40-50% collision are best explained for fluidvis- cosity η/s=0.08. In very central 10-20% collisions however, ALICE data prefer ideal fluid rather than a viscous fluid. We conclude that nearly perfect fluid is consistent with the ALICE data forelliptic flow in 2.76 TeV Pb+Pb collisions. [1] K.Aamodt et al. arXiv: 1011.3914[nucl-ex]. [2] Victor Roy and A.K. Chaudhuri , [arXiv: 1103.2870[nucl-th]].
Electromagnetic probes / 184
47 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … /
Enhancement of thermal photon production in event-by-event hydrodynamics
Rupa Chatterjee1
Hannu Holopainen 1; Kari Eskola 1; Thorsten Renk 1
1 University of Jyvaskyla
Thermal photon emission is widely believed to reflect properties of the earliest, hottest evolution stage of the medium created in ultra-relativistic heavy-ion collisions. Previous computations of photon emission have been carried out using a hydrodynamical medium description with smooth, averaged initial conditions. Recently, more sophisticated hydrodynamical models which calculate observables by averaging over many evolutions with event-by-event fluctuating initial conditions (IC) have been developed. Given their direct connection to the early time dynamics, thermal photon emission appears an ideal observable to probe fluctuations in the medium initial state. In this work, we demonstrate that including fluctuations in the IC may lead to an enhancement of thethermal photon yield of about a factor of 2 in the region 2 < pT < 4 GeV/c (where thermal photon production dominates the direct photon yield) compared to a scenario using smooth, averaged IC. Consequently, a better agreement with PHENIX data is found. This can be understood in terms of thestrong temperature dependence of thermal photon production, translating into a sensitivity to the presence of ‘hotspots’ in an event and thus establishing thermal photons as a suitable probe to characterize IC fluctuations. Ref:arXiv:1102.4706[Hep-ph].
Pre equilibrium and initial stage and global collective dynamics / 185
Initial conditions - Theory perspectives
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Initial state fluctuations and their effect on the flow
Volodymyr Magas1
Daniel Strottman 2; Horst Stoecker 3; Laszlo Csernai 4
1 University of Barcelona 2 LANL 3 University of Frankfurt 4 University of Bergen
Substantial collective flow is observed in collisions between Lead nuclei at LHC as evidenced bythe azimuthal correlations in the transverse momentum distributions of the produced particles [1]. We perform simulations of the Pb+Pb heavy ion collisions at LHC at 1.38 + 1.38 TeV/nucl within the three module model. Our calculations, in particular, show that the v1-flow, which was rather weak at RHIC and SPS, becomes stronger at LHC. Another even more important change in the v1 behaviour with respect to the similar simulations for RHIC [2] is that the v1 now peaks in the “forward” direction [3], i.e. positive v1 peak appears now at positive rapidity, and correspondingly negative peak at negative rapidity, contrary to what was observed at RHIC.
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However, it also appears that v1 flow is extremely sensitive to the initial state fluctuations, dueto the sharp change around y=0. One has to take into account that the Center of Mass (CM) rapidity is not exactly the same for all collisions, due to random fluctuations in the initial state, where the numbers of participant nucleons from projectile and target may not be exactly the same. This leads to considerable y_{CM} fluctua- tions at large impact parameters, where the flow asymmetry is the strongest, while total number of participants is the smallest. To analyze the consequences of these fluctuations, we assumed a Gaussian y_{CM} distribution, centered at y_{CM}=0, with variance of 1 or 2 units of rapidity. Such fluctuations strongly reduce v1(y) at central rapidities, however, it still stays large enough to be observed and to demonstrate the “rotation effect” discussed above [3]. It is also important to take into account experimental rapidity cuts of ALICE detector. These cuts together with initial state CM rapidity fluctuations result also into some increase of the elliptic flow, v2(pt), putting it in better agreement with the ALICE data. 1) K. Aamodt et al. [The ALICE Collaboration], arXiv:1011.3914 [nucl-ex]. 2) B. Bauchle et al., J. Phys. G 34 (2007) s1077. 3) L.P. Csernai, V.K. Magas, H. Stocker, D.D. Strottman, arXiv:1101.3451 [nucl-th].
Jets / 187
Pion quenching and tomography from RHIC to LHC in the WHDG model
Miklos Gyulassy1 William Horowitz 2
1 Columbia University 2 University Cape Town
[email protected], [email protected]
We present parameter-free predictions from the WHDG (radiative+elastic+geometric fluctuation) energy loss model for high pT pion suppression in A+A at 2.76 and 5.5 ATeV. The input density is constrained from a rigorous statistical analysis of RHIC pi0 quenching data. The predictions are consistent with the recent charged hadron RAA data from ALICE only within the current very large systematic uncertainty (due to the unmeasured reference p + p spectrum). However, our constrained prediction of central to peripheral pion R_cp(pT), in which reference p + p spectra uncertainties cancel, is found to be over-quenched by ~two sigma relative to the charged hadron ALICE R_cp data at all pT<20 GeV. The basic tomographic assumptions in WHDG are (1) the energy loss scales linearly with the initial QGP density, rho0, and (2) that rho0 scales linearly with charge particle multiplicity dNch/dy. Under these assumptions, WHDG predicts significant difference in magnitude and pt slope pf pion RAA between RHIC and LHC. Future ALICE identified pi,K,p hadron RAA data (as well as accurate p + p and p + Pb reference data) will enable more quantitative jet tomographic tests of hard probe dynamics in strongly interacting quark gluon plasmas.
188 High resolution numerical scheme for hydrodynamic analysis of heavy ion collisions and formation of an incoming shock wave induced by reheating
Masayuki Asakawa1 Hideaki Takabe 1; Keita Takakura 1; Luca Baiotti 1; Masakiyo Kitazawa 1; Masatsugu Isse 2
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1 Osaka University 2 Kobe City College of Technology
We analyze hydrodynamic evolution of fireballs created by relativistic heavy ion collisions by applying a high resolution scheme of numerical hydrodynamics with a focus on the possibility of shock formation in the course of time evolution. The possibility of shock formation has not been taken into account seriously in numerical analysis of relativistic heavy ion collisions. State of art high resolu- tion codes which are capable of capturing shocks have not been adopted with few exceptions. The possibility of shock formation or discontinuity is an important feature of hydrodynamics, and this should be treated carefully. We have developed a computational code on the basis of Chakravarthy-Osher scheme, which is one of flux-vector splitting schemes and is known to reproduce shock waves well in numerical simu- lations for a variety of situations. When equation of states with a first order phase transition is employed, our simulation reveals the manifestations of shock wavesand shock-like structures hav- ing a sharp edge, which are blurred by numerical viscosity in previous analyses, during the time evolution of fireballs. In particular, we find a high temperature region surrounded by sharpedges owing to the reheating of matter at early stage, and the formation of incoming shock-wave induced by this high temperature region. We will clarify the mechanism that produces these novel structures and discuss their importance for the observables in heavy ion collisions.
10 / 189 Bulk viscosity of a pion gas and energy-momentum correlations
Juan Torres-Rincon1 Antonio Dobado 1; Felipe Llanes-Estrada 1
1 Universidad Complutense de Madrid
We address the bulk viscosity of a pion gas in kinetic theory. Using Unitarized Chiral Perturbation Theory for the pion interaction we show how elastic collisions control the bulk viscosity at low temperature and physical pion masses. The bulk viscosity vanishes in the limit of zero temperature, in agreement with non-relativistic arguments. The collision integral zero modes (corresponding to particle and energy conservation) are properly taken into account, as is the approximate pion chemical potential. We also propose a way of measuring the bulk viscosity in correlations of the fluctuating part of the stress-energy tensor and show how an estimate can be obtained with data in heavy ion collisions at LHC or FAIR.
Global collective dynamics / 190
ATLAS flow
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Global collective dynamics / 191
Collective flow measurements from the PHENIX Experiment
Shinichi Esumi 1
1 Institute of Physics - University of Tsukuba
Recent collective flow measurements including higher moment event anisotropy from the PHENIX experiment will be presented, the particle type, beam energy dependence and the relation with jet modification will be discussed.
Global collective dynamics / 192
Common discussion with 4 experimental speakers
Hard probes I: hadron spectra / 193
Nuclear modification factors from the CMS experiment
We report the measurement of transverse momentum spectra of the charged hadrons and photons in √sNN = 2.76 TeV PbPb collisions with the CMS detector. The nuclear modification factors are constructed by dividing the PbPb pT spectra, normalized to the number of binary collisions, by the pp references.
Hard probes I: hadron spectra / 194
Recent R_{AA} Results from the PHENIX Experiment
Hard probes I: hadron spectra / 195
Common discussion with 4 speakers
Hard probes II: true jets / 196
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Jet measurements by the CMS experiment in pp and PbPb colli- sions
The energy loss of fast partons traversing the strongly interacting matter produced in high-energy nuclear collisions is one of the most interesting observables to probe the nature of the produced medium. The multipurpose Compact Muon Solenoid (CMS) detector is well designed to measure these hard scattering processes with its high resolution calorimeters and high precision silicon tracker. Analyzing data from pp and PbPb collisions at a center-of-mass energy of 2.76 TeV parton energy loss is observed as a significant imbalance of dijet transverse momentum. To gain further understanding of the parton energy loss mechanism the redistribution of the quenched jet energy was studied using the transverse momentum balance of charged tracks projected onto the direction of the leading jet. In contrast to pp collisions, a large fraction the momentum balance for asymmetric jets is found to be carried by low momentum particles at large angular distance to the jet axis. Further the fragmentation functions for leading and subleading jets were reconstructed and are compared to model calculations and measurements in pp collisions. The results confirm and complement earlier CMS results based on calorimeter jets and yield a detailed picture of parton propagation in the hot QCD medium.
Hard probes II: true jets / 197
ATLAS jet measurements
Hard probes II: true jets / 198
Common discussion with 4 speakers
Heavy flavor and Quarkonia in medium / 199
Heavy-flavor production in PbPb collisions at the LHC measured with the ALICE detector
The ALICE experiment studies nucleus–nucleus collisions at the LHC in order to investigate the properties of QCD matter at extreme energy densities. The measurement of open charm andopen beauty production allows to investigate the mechanisms of heavy-quark propagation, energy loss and hadronization in the hot and dense medium formed in high-energy nucleus-nucleus collisions. In particular, in-medium energy loss is predicted to be different for massless partons (light quarks and gluons) and heavy quarks at moderate momentum. The ALICE apparatus allows us to measure open heavy-flavour particles in several decay channels and with a wide phase-space coverage.
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We present the first results on the nuclear modification factors for heavy flavour particle production in Pb–Pb collisions at psNN = 2.76 TeV. Using proton–proton and lead–lead collision samples at ps = 7 TeV and psNN = 2.76 TeV, respectively, recorded during 2010, nuclear modification factors RAA(pt) were measured for D mesons at central rapidity (via displaced decay vertex reconstruction), and for electrons and muons from heavy flavour decays, at central and forward rapidity, respectively.
Heavy flavor and Quarkonia in medium / 200
Common discussion with 3 speakers
Heavy flavor and Quarkonia in medium / 201
Quarkonium measurements at the LHC with the ALICE detec- tor
ALICE detector has excellent performances to study quarkonium production in heavy-ion collisions at the LHC collider [1]. In this new energy regime, charmonium could reveal a privileged probe to study the properties of the high-density strongly interacting system formed in the early stages of high-energy heavy-ion collisions [2]. Bottomonium resonances will be abundantly produced, providing new constrains on theoretical models of quarkonium dissociation in QCD matter [1]. Additionally, ALICE will study quarkonium production in proton-proton collisions in which high particle multiplicity events could lead to the formation of high energy density matter as in heavy ions collisions [3]. In ALICE [4], quarkonium is measured down to pT = 0 via their mu+mu− decay channels in the ALICE muon spectrometer and via their e+e- in the ALICE central barrel. After a short description of the apparatus, the transverse momentum and rapidity distributions of inclusive J/Psi production cross section in proton-proton collisions at LHC energies will be presented. We will discuss the dependence on charged particle multiplicity of J/Psi yield in proton-proton collisions at sqrt(s) = 7 TeV. The number of reconstructed tracklets (η<1.6) in the silicon pixel detector is exploited tomeasure the charged particle density at mid- rapidity. Finally, the analysis of the inclusive J/Psi production in Pb-Pb collisions at a centre of mass energy of sqrt(sNN) = 2.76 TeV will be described. Preliminary results on the nuclear modification factor (RAA) and the central to peripheral nuclear modification factor (RCP) will be shown.
[1] ALICE collaboration, PPR II, J. Phys. G32, 1295 (2006) [2] P. Braun-Munzinger and J. Stachel, Phys. Lett. B490, 196 (2000); R.L. Thews, M. Schroedter and J. Rafelski, Phys. Rev. C63, 054905 (2001); A. Andronic et al., Phys. Lett. B571, 36 (2003); L. Grandchamp, R. Rapp and G.E. Brown, Phys. Rev. Lett., 92, 212301 (2004). [3] K. Werner et al. arXiv:1010.0400v1 (2011); K. Werner et al., Phys. Rev. Lett. 106, 122004 (2011). [4] ALICE collaboration, J. Instrum. 3, S08002 (2008).
Heavy flavor and Quarkonia in medium / 202
Common discussion with 2 speakers
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203
Hadrochemistry – theory status
204
ALICE hadrochemistry
205 common discussion with 2 speakers
Correlations & fluctuations / 206
STAR: results from the beam energy scan program
Correlations & fluctuations / 207
NA49/NA61: SPS results on fluctuations & correlations
Correlations & fluctuations / 208
Production of identified particles in pp and PbPb collisions at LHC energies with the ALICE detector
The ALICE experiment is taking data since 2009, with proton and lead beams. In this talk, wereview the different particle identification techniques used by the experiment and the excellent performance during the first year of data taking. We summarize the current results on identified particle spectra in pp collisions at sqrt(s) = 900 GeV and 7 TeV, and in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. In particular, the energy dependence of the spectral shapes of the pp data is discussed and the results are compared to previous experiments and commonly used Monte Carlo models. The evolution of the particle spectra in PbPb with collision centrality is presented. Various particle ratios are
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shown, including the baryon/meson ratio (Lambda/K0s). Finally, we conclude with an overview of the ongoing analyzes on identified particles.
Correlations & fluctuations / 209
Correlations and fluctuations measured by the CMS experiment in pp and PbPb collisions
Measurements of charged dihadron angular correlations are presented in proton-proton (pp) and Lean-Lead (PbPb) collisions, over a broad range of pseudorapidity and azimuthal angle, using the CMS detector at the LHC. In very high multiplicity pp events at center-of-mass energy of 7 TeV, a striking “ridge”-like structure emerges in the two-dimensional correlation function for particle pairs with intermediate pT of 1-3 GeV/c, in the kinematic region 2.0 < |Delta eta| < 4.8 and small Delta Phi, which is similar to the observation in heavy-ion collisions. Updated studies of this new effect as a function of particle transverse momentum, rapidity and event characteristics are shown and discussed in comparison to various model calculations. The long-range and short-range dihadron correlations are also studied in PbPb collision at a nucleon-nucleon center-of-mass energy of 2.76 TeV. The dependence of the jet-and ridge-region shape and yield on transverse momentum and collision centrality has been measured. A Fourier analysis of the long-range dihadron correlations will be presented and discussed in the context of CMS measurements of higher order flow coefficients.
New challenges / 210
The low energy frontier of A-A
New challenges / 211
Physics opportunities of future p-A runs
New challenges / 212
Physics opportunities of e-A colliders
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213
Physics opportunities of e-A colliders
214
The high energy frontier of A-A
Future facilities and experiment upgrades / 215 eA collisions at the Large Hadron-electron Collider
Nestor Armesto Perez1
1 Universidade de Santiago de Compostela
I will show the possibilities for electron-ion studies offered by the proposed electron-hadron col- lider at CERN, the Large Hadron-electron Collider [1]. After a short introduction on open problems at small x, I will briefly present the machine and detector. Then I will focus on small-x aspectsin electron-nucleus collisions, first on inclusive measurements and the determination of nuclear par- ton densities, and then on diffraction. I will finish by discussing some opportunities for finalstate studies. [1] M. Klein et al., Prospects for a Large Hadron Electron Collider (LHeC) at the LHC, EPAC’08, 11th European Parti cle Accelerator Conference, 23- 27 June 2008, Genoa, Italy; http://cern.ch/lhec.
216
Hadrochemistry – theory status
217
ALICE hadrochemistry
218 common discussion with 2 speakers
73 / 222
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Quark production far from equilibrium
Daniil Gelfand1; Jens Pruschke1; Jürgen Berges1
1 TU Darmstadt
We show that quantum effects dramatically enhance the production of quarks during nonequilib- rium bosonic instabilities. Standard semi-classical descriptions based on the Dirac equation with a homogeneous background field fail to describe nonequilibrium fermion production in presence of non-perturbatively high boson occupation numbers. Our analysis goes beyond this approximation by taking into account quantum corrections including scattering and decay processes, as well as off-shell and memory effects. This is done in a quark-meson model by using two-particle irreducible (2PI) effective action techniques, which we compare to results from real-time lattice simulations. Asa consequence fermions rapidly approach a quasi-stationary distribution with a thermal occupancy in the infrared, while bosons enter a turbulent scaling regime. We also illustrate the transition between a quasi-particle like excitation spectrum towards a strongly correlated medium.
125 / 224 The Very High Momentum Particle Identification Detector atAL- ICE
Gergo Hamar1
1 MTA KFKI RMKI Research Institue for Particle and Nuclear Physics
Based on the results in the RHIC heavy ion experiments the identification of very high pT particles seems to be extremely interesting at LHC energies. ALICE performes an excellent event by event PID below 5 GeV/c even in those high track densities. However, the track-by-track analysis of the heavy ion data demands further efforts on the experimental side. We are presenting the idea of an ALICE upgrade detector which is capable to extend the particle identification into the momentum region of 5-25 GeV/c on track-by-track basis. The Very High Momentum Particle Identification Detector (VHMPID) is a gaseous Cherenkov detector, capable to distinguish charged pions, kaons and protons/antiprotons in the above momentum window in event by event. This feature gives us the possibility to study the meson/baryon anomaly, multi jet fragmantation function, in medium effects and the same-side and away-side jet correlations. The talk is focused on design issues and technical aspects of such a detector, with present simulation and the prototype test results of the VHMPID.
74 / 225 Highly-anisotropic and strongly-dissipative hydrodynamics for early stages of relativistic heavy-ion collisions.
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Radoslaw Ryblewski1
1 Institute of Nuclear Physics PAN
A new framework of highly-anisotropic hydrodynamics is introduced [1] that includes dissipation effects. Dissipation is defined by the form of the entropy source that depends on the pressure anisotropy and vanishes for the isotropic fluid. With a simple ansatz for the entropy source obey- ing general physical requirements, we are led to a non-linear equation describing the time evolu- tion of the anisotropy in purely-longitudinal boost-invariant systems. Matter that is initially highly anisotropic approaches naturally the regime of the perfect fluid. Thus, the resulting evolution agrees with the expectations about the behavior of matter produced at the early stages of relativistic heavy- ion collisions. The equilibration is identified with the processes of entropy production. For purely longitudinal, boost-invariant expansion with small anisotropy, the proposed model agrees with the Israel-Stewart theory and Martinez-strickland model [2,3,4]. However, the model is designed to describe highly anisotropic systems where the standard dissipative hydrodynamics is not applica- ble. The proposed model of isotropization may be also used to describe non-boost-invariant systems [5] and boost-invariant systems with asymmetric transverse expansion [6]. In the latter case, we find that as long as the initial energy density profile is unchanged the calculated soft hadronic observables remain practically the same. This result indicates the insensitivity of the analyzed observables to the initial pressure anisotropy and suggests that the complete thermalization of the system may be delayed to easily acceptable times of about 1 fm/c.
1. W.Florkowski, R.Ryblewski, Phys.Rev. C83 (2011) 034907 2. M.Martinez, M.Strickland, Nucl.Phys. A848 (2010) 183-197 3. M.Martinez, M.Strickland, arXiv:1011.3056 [nucl-th] 4. R.Ryblewski, W.Florkowski, Acta Phys.Polon. B42 (2011) 115-138 5. R.Ryblewski, W.Florkowski, J.Phys.G G38 (2011) 015104 6. R.Ryblewski, W.Florkowski, arXiv:1103.1260 [nucl-th]
84 / 226 Fireball fragmentation and rapidity correlations of protons
Martin Schulc1 Boris Tomasik 1
1 Faculty of Nuclear Sciences and Physical Engineering (FNSPE)-Cze
We investigate proton rapidity correlations for a fireball that fragments due to non-equilibrium ef- fects at the phase transition from deconfined to hadronic phase. Such effects include spinodal frag- mentation in case of first order phase transition at lower collision energies and cavitation dueto sudden rise of the bulk viscosity at the crossover probed at LHC and the RHIC. The study is performed on samples of artificial events generated by means of Monte Carlo generator DRAGON. Correlation function in relative rapidity appears to be a sensitive probe of fragmentation. Resonance decays make the strength of the corre- lation even stronger. Correlation function is compared with experimental results from experiments at collision energies
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of few GeV per nucleon. We demonstrate that there is no principal disagreement between the generated and the experimental correlation functions.
QCD Phase diagram / 228
Deconfinement and chiral transition in QCD at finite tempera- ture
Peter Petreczky1
1 BNL
I will discuss new lattice results on the deconfinement and chiral aspects of the transition in QCD at nonzero temperature. I will report on calculations performed using the Highly Improved Staggered Quark (HISQ) action on Nt=6, 8 and 12 lattices. Iwill show the continuum extrapolation for several quantities that are discussed in connection with the transition at nonzero temperature as well as the determination of the chiral transition temperature in the continuum limit. I will also show new calculations with the asqtad action on Nt=12 lattices which, when combined with the previous Nt=8 HotQCD calculations, give a consistent result for the transition temperature in the continuum limit. Finally I will discuss new findings for the equation of state for HISQ and asqtad actions.
19 / 231 Jet properties in {\it p+p} and their possible modification in cold nuclear matter in STAR
Mriganka Mouli MONDAL1
1 Institute of Physics, Bhubaneswar
The intrinsic transverse momentum of partons and the possible initial and final state gluon radiation associated with hard scatterings give rise to an acoplanarity of di-jets which depends onboththe Q2 of hard scatterings and the center of mass energy of the colliding beams. Multiple scatterings of the hard scattered partons in cold nuclear matter may also alter the measured acoplanarity when compared to those in {\it p+p}. Studies in central {\it d+Au} collisions are therefore vital to disentangle medium-induced kt broadening from initial state nuclear effects and any potential broadening due to jet quenching in the medium produced in heavy-ion collisions. While full jet reconstruction is a direct way to study such acoplanarities, di-hadron correlations with respect to a high momentum leading particle can also be utilized as a complementary tool.
Two quantities commonly used to characterize the properties of jets are jt, the transverse momentum of the jet fragments relative to the jet axis, and kt, the transverse√ component√ of the momentum of ⟨ 2⟩ ⟨ 2⟩ the hard scattered√ partons. Measurements of the jet parameters, jt and kt at STAR in {\it p+p} collisions at s = 62.4, 200 and 500 GeV extracted from di-hadron correlations are presented. 0 π (Et = 6.5 to 18.5 GeV) and charged tracks√ (pt = 3.0-8.5 GeV/c) are used as trigger particles in these analyses. The results extracted at s = 200 GeV will be compared to those using full jet reconstruction and contrasted to measurements made for several {\it d+Au} centralities.
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96 / 232 Cavitation and Thermal Dilepton Production in QGP
Sreekanth V.1 Hiranmaya Mishra 1; Jitesh Bhatt 1
1 Physical Research Laboratory, Ahmedabad, India
We investigate the thermal dilepton production-rates using one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temper- ature. We study the \textit{non-ideal} effects arising due to viscosity (both bulk and shear), equation of state (ϵ ≠ 3P ) and cavitation on thermal dilepton production from QGP at RHIC energies. The effect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consis- tent with recent lattice QCD estimates. It is shown that the \textit{non-ideal} gas equation ofstate i.e ϵ − 3P ≠ 0 behavior of the expanding plasma, which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the dilepton production-rates. We calculate the first order corrections to the dilepton production rates dueto shear and bulk viscosities. It is shown that ignoring the cavitation can lead to a wrong estimation of the particle spectra. We show that the shear viscosity can enhance the thermal dilepton spec- tra whereas the bulk viscosity can suppress it. We present the combined effect of bulk and shear viscosities on the dilepton spectra.
42 / 233 D+ →K- π+ π+ Production in pp collisions at LHC with the ALICE detector
Bala Renu1
1 INFN,Turin
ALICE is the dedicated heavy-ion experiment at the LHC. Its main physics goal is to study the prop- erties of the strongly-interacting matter in the conditions of high energy density (>10 GeV/fm3 )and high temperature (> 0.3 GeV) expected to be reached in central Pb-Pb collisions. Charm and beauty quarks are a powerful tool to investigate this high density and strongly interacting state of matter as they are produced in initial hard scatterings, and due to their long life time, they probe allthe stages of the system evolution. The measurement of charm production cross section in pp collisions provides interesting insight into QCD processes and is important as a reference for heavy ion stud- ies. Here, we will present the strategy adopted to measure the cross section of one of the hadronic decay channel, D+→ K- π+ π+ , in pp collisions at LHC energies. The first preliminary cross section results obtained for the same channel will also be shown.
11 / 234 First results from hybrid HKM for top RHIC and LHC energies
Iurii Karpenko1 Klaus Werner 2; Yuriy Sinyukov 1
1 Bogolyubov Institute for Theoretical Physics 2 SUBATECH, University of Nantes
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The hydrokinetic approach [1,2] to A+A collisions describes hydrodynamic expansion ofsystems created in A+A collisions and their dynamic decoupling according to particle liberation probabilities in a way inspired by Boltzmann equation. The up-to-date version of hydro-kinetic model include the realistic features of heavy ion collisions typical for RHIC and LHC energies in the way directed by the papers [3,4]:
• The equation of state (EoS) is constructed for the case of crossover QGP-HG phase transition and combines lattice-QCD inspired results for QGP phase and ideal gas mixture of all hadron species, well-established by Particle Data Group (326 sorts). • Gradual decay of short-lived resonances into expanding hadronic system according to their widths define the composition of the gas and hence its EoS at each space-time points. The decayscon- tribute also to emission function and hence to the particle spectra. • The cross-sections and collision rates in the hadronic gas are calculated in accordance withthe UrQMD model. • Initial conditions for hydrodynamic evolution are taken from Glauber or CGC approaches.
Switching to the transport code (UrQMD) is performed at the space-like hypersurface with essen- tially non-equilibrium hadron distribution functions calculated in hydro-kinetic approach. This es- sential extension of the model permits one to calculate the tails of hadron scatterings at low-density final stage. With the model given, a reasonable description of transverse momentum spectra for several sorts of hadrons and pion HBT radii is achieved for top RHIC energy. The reproduction of recent ALICE LHC femtoscopic results is also presented. [1] Yu.M. Sinyukov, S.V. Akkelin and Y. Hama 2002 Phys. Rev. Lett. 89, 052301. [2] S. V. Akkelin, Y. Hama, Iu. A. Karpenko, and Yu. M. Sinyukov, Phys. Rev. C 78, 034906. [3] Iu.A. Karpenko, Yu.M. Sinyukov, Phys.Lett.B 688 (2010), 50-54. [4] Iu.A. Karpenko, Yu.M. Sinyukov, Phys.Rev.C 81 (2010), 054903.
43 / 235
Non−Photonic Electron and√ Charged Hadron Azimuthal Corre- lation in p+p Collisions at s = 500 GeV in STAR
Wei Li1
1 Shanghai Institute of Applied Physics
RHIC measurement on non-photonic electrons from heavy quark decays shows similar suppression as light hadrons at high pT in central Au+Au collisions. However, the interpretation is complicated by the combined contributions from charm and bottom decays. Non-photonic electron and charged hadron azimuthal√ correlation has been used as a powerful tool to disentangle charm and bottom contributions at s = 200 GeV up to pT ~ 9 GeV/c. Combining the non-photonic electron RAA and the relative bottom decay contribution in p + p collisions suggests the bottom decay electrons are also suppressed in central Au+Au collisions. We will report the preliminary results of non-photonic electron and charged√ hadron azimuthal cor- relation at midrapidity for 6.5 61 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 97 / 236 √ Dielectron production in Au+Au collisions at sNN = 39 GeV at STAR Patrick Huck1 1 CCNU + IKF + LBNL During the beam energy scan in 2010 a wide range of beam energies has been explored for Au+Au collisions using the STAR detector at RHIC. With minimum material budget in the tracking part of the detector this run is particularly suited for the investigation of virtual photons originating from the hot and dense medium created in heavy ion collisions. The completed installation of the STAR time-of-flight detector is a further distinctive feature which allows the particles’ velocity tobeused for particle identification in addition to their energy loss in the time projection chamber. As electro- magnetic probes, dielectron pairs do not interact strongly with the medium and hence carry direct information of its properties at the time of production. Thus, measurements of dielectron emissivity in heavy ion collisions provide√ an additional tool for the study of the quark gluon plasma. For a center-of-mass energy of sNN = 39 GeV , 170M events have been taken. The poster presents the status of an ongoing dielectron analysis of this high statistics sample. It concentrates on particle identification, background rejection and subtraction, and the reconstruction of dielectron pairsup e+e− 2 to Minv = 3.5 GeV /c . 123 / 237 QGP viscosity coefficients: from weak to strong coupling Marcus Bluhm1 Burkhard Kampfer 2; Krzysztof Redlich 3 1 Laboratoire SUBATECH 2 Helmholtz-Zentrum Dresden-Rossendorf & Technical University Dresden 3 Wroclaw University By means of high energy nuclear collisions, the properties, such as the viscosity coefficients, of QCD matter under extreme conditions are intended to be experimentally revealed. One remarkable result from collisions at RHIC is that the produced hot matter is an almost ideal fluid, obeying the smallest shear viscosity to entropy density ratio observed in nature. Employing an effective kinetic theory for quasiparticle excitations featuring dynamically generated self-energies, we determine the temperature dependence of the viscosity coefficients of deconfined strongly interacting matter [1,2]. This knowledge may serve as input forthe phenomenological description of heavy-ion collisions at LHC and RHIC. Exhibiting the parametric dependencies known from perturbative QCD at large temperatures, the extrapolation of our results into the non-perturbative region shows fairly nice quantitative agreement with lattice QCD results in the case of a pure gluon plasma.We find a minimum in the specific shear viscosity and a rapid increase of the specific bulk viscosity near the deconfinement transition temperature T_c. The ratio of bulk to shear viscosity comprises 62 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / both, a quadratic dependence on the conformality measure at large temperatures as known from pQCD as well as a linear dependence near T_c as known from specific strongly coupled and nearly conformal theories based on gauge/string duality [3]. Thus, the exploited framework provides a systematic interpolation between both regimes of weak and strong coupling. [1] M. Bluhm, B. Kampfer, K. Redlich, Nucl. Phys. A 830 (2009) 737C [2] M. Bluhm, B. Kampfer, K. Redlich, arXiv:1011.5634 [3] M. Bluhm, B. Kampfer, K. Redlich, arXiv:1101.3072 98 / 238 Equation of state of strongly interacting matter: spectra for ther- mal particles and intensity correlation of thermal photons Somnath De1 Dinesh Srivastava 1; Rupa Chatterjee 2 1 Variable Energy Cyclotron Centre 2 University of Jyvaskyla [email protected], [email protected], [email protected] We find that an equation of state for hot hadronic matter consisting of all baryons having M < 2 GeV and all mesons having M < 1.5 GeV, along with Hagedorn resonances in thermal and chemical equilibrium, matches rather smoothly with lattice equation of state (p4 action, Nτ = 8) for T up to ≈ 200 MeV, when corrected for the finite volume of hadrons. Next we construct two equations of state for strongly interacting matter; one, HHL, in which the above is matched to the lattice equation of state at T = 165 MeV and the other, HHB, where we match it to a bag model equation of state with critical temperature Tc = 165 MeV. We compare parti- cle spectra, thermal photon spectra and histories of evolution of the quark-gluon plasma produced in the central collision of gold (lead) nuclei at RHIC (LHC) energies, considering ideal hydrodynamical expansion of the system. The particle and thermal photon spectra are seen to differ only marginally, for the two equations of state. The history of evolution shows differences in the evolution oftem- perature and radial velocity, as one might expect. We calculate intensity interferometry of thermal photons and find it to be quite distinct for the two equations of state, especially for the outward correlation. The longitudinal correlation also shows a dependence on the equation of state, though, to a smaller extent. Ref: J.Phys.G G37 (2010) 115004. 99 / 239 Interference of thermal photons from quark and hadronic phases in relativistic collisions of heavy nuclei Dinesh Srivastava1 Rupa Chatterjee 2 1 Variable Energy Cyclotron Centre 2 University of Jyvaskyla [email protected], [email protected] We explore the intensity correlations for thermal photons having KT ≤ 2 GeV/c, for central colli- sions of heavy nuclei at RHIC and LHC energies. These photons get competing contributions from 63 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / the quark and the hadronic phases. This competition gives rise to a unique structure, especially in the outward correlation function, due to the interference between the photons from the two sources. The temporal separation of the two sources provides the life time of the system and theirstrengths provide the relative contribution of the two phases. The results are found to be quite sensitive tothe quark-hadron phase transition temperature and the formation time of the plasma. Ref:Phys.Rev.C80:054914 (2009) 59 / 240 Two freeze-out analysis of hadron yields and spectra at RHIC Kang Seog Lee1 Suk Choi 1 1 Chonnam National University With the two freeze-out model for the hadron production in the relativistic heavy-ion collisions, hadron ratios and their momentum spectra measured at RHIC are fitted. In this model the chemical freeze-out occurs earlier at higher temperature. In analyzing the hadron ratios, resonance contribu- tion has been carefully taken into account. After the chemical freeze-out the number of the thermal hadrons of each type is kept fixed as in-elastic collisions becomes less frequent, while the elastic col- lisions among the hadrons of the same species maintain the thermal equilibrium until the thermal freeze-out. At the thermal freeze-out the chemical potentials for each hadron species are calcu- lated from the fixed number of thermal hadrons and the transverse momentum spectra of measured hadrons are fitted with blast wave-type equation together with the resonance contribution. 44 / 241 Measurements of Non-photonic Electron Spectra and Elliptic Flow in Au+Au Collisions from STAR at RHIC Xin Li1 1 STAR Collaboration The dependence of parton energy loss on the space-time evolution oftheQCD medium is believed to be mostly responsible for the azimuthal angular anisotropy distribution of high transverse momentum (pT) particles in nucleus-nucleus collisions. Simultaneous measurements of both the nuclear modification factors and the elliptic flow parameter v2 can provide insights on parton energy loss mechanisms and space-time evolutions of the colliding system. Heavy quarks are particularly effective probes because their initial production can be reliably calculated from pQCD approaches and their final states reflect directly evolutions through the strongly interacting partonic medium created in heavy ion collisions. We will present the STAR non-photonic electron (NPE) measurements at high pT from p+p and Au+Au collisions. The data were taken during run 2009 and run 2010, where unprecedented amount of data have been collected with detector configurations for minimum photonic conversion background. Both the nuclear modification factors and the v2 measurements will be reported as a function of pT and collision centralities. Comparisons with theoretical model 64 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / calculations and possible constraints on properties of the partonic medium will be discussed. 85 / 244 Effects of final state interactions on charge separation in relativis- tic heavy ion collisions Bin Zhang1; Guo-Liang Ma2 1 Arkansas State University 2 Shanghai Institute of Applied Physics [email protected], [email protected] Charge separation is an important consequence of the Chiral Magnetic Effect. Within the framework of a multi-phase transport model, the effects of final state interactions on initial charge separation are studied. We demonstrate that charge separation can be significantly reduced by the evolution of the Quark-Gluon Plasma produced in relativistic heavy ion collisions. Hadronization and resonance decay can also affect charge separation. Moreover, our results show that the Chiral Magnetic Effect leads to the modification of the relation between the charge azimuthal correlation and the elliptic flow that is expected from transverse momentum conservation only. The transverse momentum and pseudorapidity dependences of, and the effects of background on the charge azimuthal correlation are also discussed. Reference: Effects of final state interactions on charge separation in relativistic heavy ion collisions, Guo-Liang Ma, Bin Zhang, arXiv:1101.1701 [nucl-th] 115 / 245 Nucleon mass generated from confinement and a dynamic gener- ation of the quark masses Jean-Christophe CAILLON1 1 CENBG We have built the nucleon by taking into account explicitly both confinement like in an MIT bag model and a dynamic generation of the quark masses in a Nambu Jona Lasinio model. Therefore, we have supposed a QCD vacuum modified in a cavity and thus a modified quarkcon- densate coming from the presence of three valence quarks in this cavity. Quarks acquire their masses through their interaction with this modified quark condensate which is itself determined self-consistently by the equilibrium condition for the bag : the outward pressure due to both the motion of three quarks and the modified vacuum in the nucleon must be counterbalanced bythe inward pressure of the vacuum outside the bag. We are able to pass continuously from a nucleon description in a pure MIT bag model to a description using constituent quark masses determined in an NJL model. 45 / 246 Beauty in the QGP from the lattice 65 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Jon-Ivar Skullerud1 Chris Allton 2; Don Sinclair 3; Gert Aarts 2; Maria-Paola Lombardo 4; Mehmet Bugrahan Oktay 5; Seyong Kim 6; Sinead Ryan 7 1 National University of Ireland Maynooth 2 Swansea University 3 Argonne National Laboratory 4 INFN Frascati 5 University of Utah 6 Sejong University 7 Trinity College Dublin We study the temperature dependence of bottomonium for temperatures in the range 0.4Tc < T < 2.1Tc, using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simula- tions for Nf = 2 light flavors on a highly anisotropic lattice. We find thatthe Υ is insensitive to the temperature in this range, while the χb propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behaviour consistent with nearly-free dynamics at T ≃ 2Tc. 100 / 247 Dimuon radiation at the CERN SPS within a hybrid evolution model Elvira Santini1 Marcus Bleicher 2 1 Goethe Universität Frankfurt 2 Goethe Universität Frankfurt and Frankfurt Institute for Advanced Studies (FIAS) In this talk I discuss dilepton emission from hot and dense matter created in heavy-ion collisions and present results on dimuon invariant and transverse mass spectra obtained using a hybrid approach based on the UrQMD transport model with an intermediate hydrodynamic stage for the modeling of heavy-ion dynamics. During the hydrodynamic stage, the production of lepton pairs is described by radiation rates for a strongly interacting medium in thermal equilibrium. In the low mass region, hadronic thermal emis- sion is evaluated assuming vector meson dominance including in-medium modifications of the rho meson spectral function through scattering from nucleons and pions in the heat bath. In the interme- diate mass region, the hadronic rate is essentially determined by multi-pion annihilation processes. Emission from quark-antiquark annihilation in the quark gluon plasma is taken into account as well. When the system is sufficiently dilute, the hydrodynamic description breaks down and a transition to a final cascade stage is performed. In this stage dimuon emission is evaluated as commonly done in transport models. Focusing on the enhancement with respect to the contribution from long-lived hadron decays after freezout observed at the SPS in the low mass region of the dilepton spectra, the relative importance of the different thermal contributions and of the two dynamical stages is discussed. 46 / 248 D+ analysis in Pb-Pb collisions at √ sN N = 2.76 TeV at the LHC with ALICE. 66 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Giacomo Ortona1 1 Universita & INFN, Torino A Large Ion Collider Experiment (ALICE) is one of the four experiments at the Large Hadron Col- lider (LHC), and the only one mainly dedicated to ultra relativistic heavy ion collisions, in order to investigate the properties of the high-density state of QCD matter produced in such events. The first Pb-Pb collisions at a centre of mass energy of √s = 2.76 TeV for nucleon pair were delivered by LHC in November 2010. In Pb-Pb collisions heavy quarks are regarded as sensitive probes of the interaction dynamics between the parton and the medium produced in such collisions as they are produced on a very short time scale and they follow all the evolution of the medium. At the energies available at LHC charm is produced abundantly and therefore it is possible to study the production of charm with high statistics. In this poster the analysis for D+ → K − π + π + reconstruction in Pb-Pb collisions at ALICE will be presented, along with the prospects for D+ elliptic flow and energy loss measurements. Jets / 250 Next-to-leading order analysis of inclusive jet, tagged jet and di- jet production in PbPb collisions at the LHC Ivan Vitev1 1 Los Alamos National Laboratory Jets physics is an important new area of active research at RHIC and at the LHC that paves the way for novel tests of QCD multi-parton dynamics in heavy-ion reactions. At present, perturbative QCD calculations of hard probes in “elementary” nucleon-nucleon reactions can be consistently combined with the effects of the nuclear medium up to next-to-leading order. While such accuracy isdesir- able for leading particle tomography, it is absolutely essential for the new jet observables. With this motivation, we present results and predictions at NLO for the recent LHC lead-lead (Pb+Pb) run at a center-of-mass energy of 2.76 TeV per nucleon-nucleon pair. Specifically, we focus on the suppression the single and double inclusive jet cross sections and demonstrate how the di-jet asym- metry, recently measured by ATLAS and CMS, can be related to these general results. The case of jets tagged by an electroweak boson is exemplified by the Z0+jet channel. We predict a signature transition from enhancement to suppression of the tagged jet reflective of the medium-induced mod- ification of parton showers. We also present NLO results relevant to the inclusive Z0 dataobtained by the CMS collaboration. Our analysis includes not only final-state inelastic parton interactions in the QGP, but also initial-state cold nuclear matter effects and non-perturbative hadronization cor- rections. Finally, we clarify the relation between the suppression of inclusive jets, tagged jets and di-jets and the quenching of inclusive particles on the example of the recent ALICE neutral pion attenuation data. We conclude by discussing future directions and effective theories of QCD that can help improve the accuracy of the theoretical tools for jet tomography. 47 / 251 Reconstruction of Ds mesons in the ALICE Experiment at LHC Gian Michele Innocenti1; Sadhana Dash1 1 Universita & INFN, Torino 67 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Open Charm mesons produced in relativistic nuclear reactions are among the most direct probes to investigate the medium produced in these collisions. Ds mesons act as an useful probe to study hadronization mechanism in heavy ion collisions. The study on exclusive reconstruction of theDs mesons via the decay channel (Ds->KKpi ) for p+p collisions at 7 TeV is presented. The measurement will allow us to study ratios of charmed-strange mesons to other D mesons and will act as baseline reference for the Ds measurement in heavy-ion collisions. The ALICE experiment at the LHC is designed to perform such measurements at mid-rapidity by means of its barrel tracking detectors. The barrel tracking detectors provide the momentum infor- mation and the particle identification of the charged particles together with an accurate measurement of the primary and secondary vertex positions. The study on selection cuts to optimize the combinatorial background rejection will be described. The Ds signal in the KKpi invariant mass distribution for various pT binswillbe shown. 75 / 252 Dissipative dynamics of highly anisotropic plasmas Mauricio Martinez Guerrero1 Michael Strickland 2 1 FIAS 2 Gettysburg College We present a method to improve the description of 0+1 dimensional boost invariant dissipative dynamics in the presence of large momentum-space anisotropies. Instead of using the canonical hydrodynamical expansion of the distribution function around an isotropic equilibrium state, we expand around a state which is anisotropic in momentum space and parameterize this state in terms of three proper-time and spatial-rapidity dependent pa- rameters. At leading order the result obtained is two coupled hydro-like differential equations for the momentum-space anisotropy and typical momentum of the degrees of freedom. Within this frame- work, we get both the ideal hydrodynamic and free streaming expansion as asymptotic limits. In addition, we show that when linearized the differential equations reduce to 2nd order Israel-Stewart viscous hydrodynamics. Finally, we make quantitative comparisons of the evolution of the pressure anisotropy within our approach and 2nd order viscous hydrodynamics in both the strong and weak coupling limits. We make quantitative comparisons of the evolution of the pressure anisotropy within our approach and 2nd order viscous hydrodynamics in both the strong and weak coupling limits. Finally, we comment about the generalization of this framework to non-boost invariant expansion. Global and collective dynamics / 253 Event anisotropy√ v2 of identified hadrons and light nuclei in Au+Au collisions at sNN = 7.7, 11.5 and 39 GeV with STAR Alexander Schmah1 1 Lawrence Berkeley National Lab 68 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The main goal of the RHIC Beam Energy Scan (BES) is the exploration of the QCD phase diagram in the region of a possible phase transition between the Quark Gluon Plasma (QGP) and the hadron gas phase. In the year 2010 the first part of the BES program was successfully√ accomplished by recording data from Au+Au collisions at sNN = 7.7, 11.5 and 39 GeV. The second harmonic (v2) of the azimuthal particle distribution relative to the reaction plane was found to be one of the most important observables to study the underlying dynamics in the early stage of the collisions. The number-of-constituent quark (NCQ) scaling of v2 is interpreted as a signature of deconfinement and existence of the QGP phase. At the lower energies studied it was expected to see a change in this scaling behaviour as the role of the QGP phase should diminish. We present v2 measurements at all three beam energies for 0 identified hadrons (π, K,Ks, p, ϕ, Λ, 3 Ξ) and light nuclei (d and He) as a function of pT for various collision centralities. The measured nuclei v2 are compared to the proton v2 and results from a dynamical coalescence model calculation, while the NCQ scaling is tested using all identified hadrons. For the first time, a significant difference in v2 between baryons and anti-baryons is observed. The difference increases with decreasing center-of-mass energy. 48 / 254 Centrality√ dependence of the Υ Nuclear Modification Factor at sNN = 200 GeV measured with STAR Rosi Reed1 1 STAR Suppression of quarkonia in heavy ion collisions with respect to proton-proton collisions was hy- pothesized to be a signature of the Quark Gluon Plasma (QGP). However, effects such as thesta- tistical recombination of heavy flavor quark-antiquark pairs or co-mover absorption can alsoaf- fect quarkonia production. For the bottomonium states these competing effects are expected tobe smaller than for the charmonium states. Lattice calculations show that quantifying the suppression of an entire family of quarkonium mesons can give us a model dependent measurement of the tem- perature of the matter produced in heavy√ ion collisions. For the Υ family, calculations indicate that the Υ(1S) state should not be suppressed at (s) = 200 GeV, which would give a standard candle that the Υ(2S) and Υ(3S) states can be compared to. The suppression of quarkonia can be quan- tified by calculating the nuclear modification factor RAA, which is the ratio of production in p+p scaled by the number of binary collisions to the production in Au+Au collisions. We will present√ results for mid-rapidity Υ(1S + 2S + 3S) production in p+p, d+Au and Au+Au collisions at sNN = 200 GeV. These results will be combined into RdA and RAA and compared to theoretical QCD calculations. The centrality dependence of RAA will be shown for the combined Υ(1S + 2S + 3S) yield as well as for the /Upsilon(1S) yield. The invariant yield versus transverse momentum in Au+Au collisions will also be discussed. 15 / 255 Investigating jet and non-jet contributions to long range pseudo- rapidity correlations in di-hadron measurements from STAR. 69 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Chanaka De Silva1 1 University of Houston Two particle number correlations in relative azimuth and pseudo-rapidity (∆ϕ, ∆η) develop novel features in heavy ion collisions at 200 GeV when compared to p+p results at the same energy. Earlier STAR results have shown a ∆η elongated structure for the small ∆ϕ angles (on the same- side) and the development of significant deformations at ∆ϕ aproxπ (on the away-side). In this talk we will present new results from such correlation analysis that show unambiguously formation of a double-hump structure on the away side in raw correlation measured in very central Au+Au collisions for intermediate pT (2 Jets / 256 Leading hadron PID effects in di-hadron angular correlations in STAR Kolja Kauder1 1 University of Illinois at Chicago Hard scatterings of partons provide a valuable colored probe ofthe strongly-coupled medium created in ultra-relativistic heavy ion collisions. These hard scatterings can be studied by means of angular correlations of charged hadrons with respect to a high transverse momentum trigger particle. Several recent two-particle correlation studies indicate that A+A collision dynamics evolve significantly with collision centrality. They specifically reveal the presence of unexpected strong away-side deformation and the development of a long-range “ridge” in correlation measured as a function of ∆η vs ∆ϕ. The detailed physics mechanisms responsible for these features however remain under active investigation. We will present preliminary results of a new di-hadron correlation analysis, measured as a function of ∆ϕ vs ∆η, for identified high-pT triggers from the high-statistics 200 GeV Au+Au data sample collected by the STAR experiment at RHIC during Run-10. The relativistic rise of the ionization energy loss dependence of 70 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / particles measured in the STAR TPC is used to obtain a statistical separation of charged pions, kaons, and protons. The ∆ϕ vs ∆η correlations measured in this work extend earlier measurements of azimuthal correlations (in ∆ϕ only) with identified hadron triggers, which, admittedly with large uncertainties, reported no significant dependence on a leading hadron identity. The added ∆η dimension and improved statistics reveal a rich set of new features: the near-side (|∆ϕ| < 1) associated hadron distributions with respect to high-pT pion, kaon and proton triggers exhibit distinctly different features for both “ridge” (large ∆η and small ∆ϕ) and “jet-like” (|∆ϕ| < 0.7 excluding the ridge) particles. We will discuss the implications of these results in the context of the existing models and possible connection of the leading hadron ID with the color-charge and/or flavor of a hard-scattered parton. QCD Phase diagram / 257 Charge fluctuations in chiral models and the QCD phase transi- tion Vladimir Skokov1 Bengt Friman 1; Krzysztof Redlich 2 1 GSI, Darmstadt, Germany 2 Wroclaw University, Poland Fluctuations of conserved charges are key probes of the chiral phase transition in a QCD medium. Of particular phenomenological importance are studies of such fluctuations at finite baryon density. A valuable tool for assessing critical fluctuations andthether- modynamics at non-vanishing baryon density is provided by effective chiral models. We consider the Polyakov loop-extended two flavors chiral quark–meson model (PQM) and dis- cuss critical phenomena related with the spontaneous breaking of chiral symmetry. The model is explored beyond the mean-field approximation in the functional renormalisation group (FRG) ap- proach. We formulate and solve the renormalization group flow equation for the scale-dependent thermody- namic potential in the presence of the gluonic background field at finite temperature and density [1] and determine the phase diagram of the PQM model in the FRG approach [2]. We also consider prop- erties of the net-quark number density fluctuations as well as their higher cumulants [3] and discuss the influence of nonperturbative effects on their properties near the chiral crossover transition. With increasing net-quark number density, the higher order cumulants show a strong dependence on the chiral crossover transition. This is illustrated by exploring the ratios of moments of net-baryon num- ber and electric charge fluctuations. We discuss their role as probes of deconfinement and the chiral phase transition in heavy ion collisions at RHIC and LHC. [1] V. Skokov, B. Stokic, B. Friman, K. Redlich, Phys.Rev.C82:015206,2010. [2] V. Skokov, B. Friman, K. Redlich, arXiv:1008.4570 [3] B. Friman, F. Karsch, K. Redlich, V. Skokov, arXiv:1103.3511 140 / 258 Roles of Axial Anomaly on Neutral Strongly Interacting Matter 71 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / —- New Critical Points at Low Temperature and the Absence of Chromomagnetic Instabilty —- Teiji Kunihiro1; zhao zhang2 1 Kyoto University, Japan 2 North China Electric Power University,China [email protected], [email protected] We investigate effects of the axial anomaly term with a chiral-diquark coupling on the phase diagram within a two-plus-one-flavor Nambu-Jona-Lasinio (NJL) model under the charge-neutrality and β- equilibrium constraints. We find that when such constraints are imposed, the new anomaly term plays a quite similar role as the vector interaction does on the phase diagram, which the present authors clarified in a previous work. Thus, there appear several types of phase structures with multiple critical points at low temperature T , although such phase diagrams with low-T critical point(s) are never realized without these constraints even within the same model Lagrangian. This drastic change is attributed to an enhanced interplay between the chiral and diquark condensates due to the anomaly term at finite temperature; the u-d diquark coupling is strengthened by the relatively large chiral condensate of the strange quark through the anomaly term, which in turn definitely leads to the abnormal behavior of the diquark condensate at finite T , inherent to the asymmetric quark matter. We also show that the chromomagnetic instability of the neutral asymmetric homogenous two-flavor color superconducting(2CSC) phase is suppressed and can be even completely curedby the enhanced diquark coupling due to the anomaly term and/or by the vector interaction 49 / 259 J/psi analysis in proton+proton at 7 TeV in the ALICE muon spec- trometer using a pT - y correction method. Bruno Alexandre Boyer1 1 Institut de Physique Nucleaire (IPN)-Universite de Paris-Sud (Pa ALICE (A Large Ion Collider Experiment) is the LHC experiment dedicated to the study of the Quark Gluon Plasma (QGP) using heavy-ion collisions. Heavy quarkonium measurements in pp collisions are very important to constraint the different models available and as a reference for heavy ion collisions. Acceptance x efficiency corrections are a fundamental step of the analysis in orderto extract the cross-section. In this poster, I will present a J/psi inclusive analysis in the diumon channel on a large sample of pp data at 7 TeV. Acceptance and efficiency corrections will be performed asa function of the transverse momentum and rapidity on the J/psi. 141 / 260 Search for the QCD Critical Point: Higher Moments of Net-proton, Net-charge Multiplicity Distributions from the RHIC Beam En- ergy Scan Xiaofeng Luo1 1 University of Science and Technology of China (USTC); Lawrence Berkeley National Lab (LBNL) 72 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / One of the main goals of the RHIC Beam Energy Scan (BES) program is to search for the QCD critical point and the phase boundary in the QCD phase diagram. Due to high sensitivity to correlation length and direct connection to thermodynamical susceptibilities calculated in Lattice QCD and the Hadron Resonance Gas (HRG) model, higher moments of event-by-event net-proton and net-charge multiplicity distributions are used to search for the QCD critical point. In this talk, we will present various moments (variance (σ2), skewness (S), kurtosis (κ)) and moment products (κσ2 and Sσ) of the net-proton, net-charge multiplicity distributions measured by STAR detector at RHIC. The moment products κσ2 and Sσ of net-proton (net-charge) distributions are related to baryon (charge) number susceptibility ratios and are volume independent. The mix-ratio of the moments of proton and kaon multiplicities, which are predicted to be without any dependence on model parameters including the correlation length , will be also presented to establish the baselines. The√ data presented in this talk will include the measurements√ from Au+Au collisions at energies sNN = 7.7, 11.5 and 39 GeV collected in the 2 year 2010 and sNN = 200 GeV in the year 2004. Deviations from HRG models for κσ and Sσ of net-proton and net-charge distributions are observed for BES energies. 12 / 261 Multihadron production in hadronic and nuclear collisions Edward Sarkisyan-Grinbaum1 Alexander Sakharov 2 1 CERN 2 Wayne University The energy-dependence of charged particle mean multiplicity and pseudorapidity density at midra- pidity measured in nucleus-nucleus and (anti)proton-proton collisions are studied in the entire avail- able energy range. The study is performed using a model, which considers the multiparticle production process according to the dissipating energy of the participants and their types, namely a combination of the constituent quark picture together with Landau relativistic hydrodynamics. The model reveals interrelations between the variables under study measured in nucleus-nucleus and nucleon-nucleon collisions. Measurements in nuclear reac- tions are shown to be well reproduced by the measurements in pp/pbarp interactions up to RHIC energies. Heavy-ion measurements at the LHC are discussed. 50 / 262 Prospects for charm RAA in PbPb collisions at LHC via D0->Kpi reconstruction in ALICE Davide Caffarri1 1 Universita degli Studi di Padova- INFN Padova & CERN The main goal of the ALICE experiment is the investigation of the properties of strongly-interacting matter in a very high density deconfined state, that is thought to be formed in Pb-Pb collisionsat LHC. The ALICE experiment has collected Pb-Pb data at sqrt{s_NN} = 2.76 TeV and p-p data bothat sqrt{s} = 7 and 2.76 TeV. In Pb-Pb collisions, heavy quarks are sensitive probes to test the medium properties, as they are formed at shorter time scale with respect to the deconfines state. These quarks can interact withthe medium via collisional and radiative energy loss. The nuclear modification factor (RAA), obtained 73 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / comparing p-p and Pb-Pb pT-differential distributions, allows to measure the effect of in-medium energy loss. We will present the prospects for the first open charm energy loss measurement, considering the D0 in Kπ decay channel. The reconstruction of this decay channel exploits the excellent tracking, vertexing and particle identification capabilities of the ALICE experiment. Future facilities and experiment upgrades / 263 STAR science for the coming decade Carl Gagliardi1 1 STAR Collaboration The STAR Collaboration has identified eight key questions that will drive RHIC science duringthe coming decade, six of which involve ultrarelativistic heavy-ion collisions. What is the nature of the initial state in nuclear collisions? What are the properties of the strongly-coupled system pro- duced at RHIC, and how does it thermalize? Are the interactions of energetic partons with QCD matter characterized by weak or strong coupling, and what is the detailed mechanism forpartonic energy loss? Where is the QCD critical point and the associated first-order phase transition line? Can we strengthen current evidence for novel symmetries in QCD matter and open new avenues? What exotic particles are created at RHIC? The STAR detector, with its large acceptance tracking, calorimetry, and particle identification, is an ideal tool to explore these questions. Complete an- swers nonetheless will require detector upgrades. Near-term upgrades, including the Heavy Flavor Tracker and Muon Telescope Detector, will enable a rich program of heavy flavor physics. Upgrades to the forward region will enable detailed studies of the partonic structure of nuclei and the onset of gluon saturation. An additional suite of upgrades during the latter part of the decade will position STAR to make crucial measurements in e+p and e+A collisions during the early phase of eRHIC. The talk will provide an overview of this STAR decadal plan. 126 / 264 Development of the CBM RICH detector Tariq Mahmoud1 RICH Collaboration CBM 2 1 Universität Gießen 2 – The Compressed Baryonic Matter (CBM) experiment is the future heavy-ion experiment atFAIR being designed to explore the intermediate range of the QCD phase diagram in a beam energy inter- val of 10-45 AGeV. With its physics program CBM will investigate the properties of dense baryonic matter and the expected phase transition between hadronic and partonic matter. Among thekey observables are low-mass vector mesons and charmonium decaying into lepton pairs. In CBM, elec- trons with energies lower than 8 GeV/c will be identified through a RICH detector being developed at several laboratories. In addition the detector will improve the kaon/pion separation at momenta higher than 4 GeV/c. The proposed concept of the RICH detector foresees CO2 as radiator gas, spherical glassmirrors reflecting the Cerenkov radiation on an array of Multianode Photomultipliers (MAPMTs) asphoto detectors. 74 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / CO2 has been chosen because it has a Lorenz factor, gth, of 33.3, a radiation length of 183 m and a pion momentum threshold for Cerenkov light production of 4.65 GeV/c, it represents a very good compromise to fulfill the CBM RICH requirements. The mirror system will be of approximately 11.8 m² with a curvature radius of 3 m and athickness of 6 mm. For the reflective coating Al+MgF2 are foreseen. In order to cover a spherical mirror wall with a radius of 3 m, square mirror tiles of approximately 40×40cm² will be used. Regarding the photo detector investigations indicated that the 64 channel Hamamatsu H8500 MAPMT is one of the most promising candidates for the CBM RICH. The main criteria for the readout of this MAPMT are the high interaction rates (up to 10 MHz) and the challenging high level triggers in CBM. To cope with these facts a self triggered readout electronics is foreseen. The Front End Electronics (FEE) will be based on a further development of the so called n-XYTER chip which was developed for the readout of silicon detectors. The chip offers 128 channels at a readout speed of 32MHz.As an intermediate solution the high gain of the MAPMT is currently matched to the existing chip via a charge attenuator board. These components were successfully tested in laboratories and in several test beams. Single photon counting and Cerenkov light detection confirmed the suitability of the FEE and MAPMT setup.The tests also show that uncorrelated noise can be well separated from the signal using available timing information. The usage of wavelength shifter films in order to enhance the quantum efficiency ofthe MAPMT for wavelengths below 300 nm is investigated. An industrial provider for mirror prototypes with promising surface homogeneity and reflectivity has been found. The concept of the RICH detector as well as results of several tests will be presented. They arevalu- able experience for the preparation of a full scale RICH prototype setup currently under construction and to be tested at CERN in fall 2011. 13 / 265 Dynamical equilibration of strongly-interacting ’infinite’ parton matter within a Parton-Hadron-String Dynamics (PHSD) trans- port approach Vitalii Ozvenchuk1 1 FIAS I study the kinetic and chemical equilibration in ‘infinite’ parton matter within the Parton-Hadron-String Dynamics transport approach, which is based on a dynamical quasiparticle model for partons matched to reproduce lattice-QCD results – including the partonic equation of state – in thermodynamic equilibrium. The ‘infinite’ matter is simulated within a cubic box with periodic boundary conditions initialized at different energy density. Different thermodynamical distributions of the strongly-interacting quark-gluon plasma (sQGP) are addressed and discussed. Theory developments / 266 Jets in QCD media: from color coherence to decoherence 75 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Yacine Mehtar-Tani1 Carlos Salgado 1; Konrad Tywoniuk 2 1 University of Santiago de Compostela 2 Lund University Jet physics in hadronic collisions is one of the major achievements of perturbative QCD. However, a complete theory of jets in a hot and dense partonic environment remains to be developed. Such a theory is needed in Heavy-Ion Collisions (HIC), at RHIC and now at the LHC, in order to have a clean access to the properties of the Quark-Gluon Plasma (QGP). To this end, we have investigated medium modification of the radiation pattern of a quark-antiquark antenna traversing a dense medium in order to understand how the QGP alters color coherence which is an important feature of the intRAjet structure in vacuum. In contrast to gluon radiation in vacuum, and unexpectedly, we find a strict geometrical separation between in-vacuum and medium- induced gluon radiation. Also, a soft logarithmic divergence appears pointing to the possibility of resuming multiple gluon branching in the cascade. Moreover, in the case of an opaque medium near the unitarity bound, a simple and intuitive physical picture arises : the interaction with the QGP leads to the gradual decoherence of the pair yielding a universal radiation pattern which does not depend on the initial color configuration of the antenna. These results are in qualitative agreement with the recent ATLAS and CMS data and provide astart- ing point for further studies on in-medium jet modification. Heavy Flavors / 267 Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC Alfredo Molinari1; Andrea Beraudo2; Arturo De Pace3; Francesco Prino3; Marco Monteno3; Marzia Nardi3; Wanda Maria Alberico1 1 Dip.Fis.Teor.Univ.Torino/INFN Torino 2 Centro Fermi/CERN 3 INFN Torino The understanding of the heavy-quark dynamics in nucleus-nucleus collisions, so far possibleat RHIC only through the inclusive measurement of electron spectra from c and b decays, is becoming now accessible at LHC also through the exclusive reconstruction of open-charm hadrons, thus pro- viding a richer physical information useful to discriminate among different theoretical models. A complete setup to study heavy-flavor observables in pp and AA collisions was recently developed by us: in the latter case the presence of a hot fireball leads to a modification of the final p_T-spectra. More specifically, the propagation of c and b quarks in the plasma (whose evolution is supposed to be described by relativistic hydrodynamics) is followed by solving the relativistic Langevin equation within a picture of multiple uncorrelated random collisions. The relevant heavy-quark transport coefficients are given a microscopic evaluation within the Hard Thermal Loop approximation, sup- plemented by a kinetic pQCD calculation for hard collisions. The results obtained with this approach turned out to be in reasonable agreement with the experimental data obtained at RHIC, in particular for the R_AA of non-photonic electrons. Here we extend the above study to the LHC case, at the current center-of-mass energy of 2.76 TeV. The first data on primary charged particle density obtained by the ALICE collaboration (dN_ch/deta~1600 in central PbPb collisions) allow to provide an estimate of the initial conditions of the hydrodynam- ical evolution of the background medium. First results for the spectra, the R_AA and v_2 of open- charm hadrons and non-photonic single-electrons will be presented. 76 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 14 / 268 Dissipative hydrodynamics for relativistic multi-component sys- tems Andrej El1 Carsten Greiner 1; Francesco Lauciello 1; Ioannis Bouras 1; Zhe Xu 1 1 University of Frankfurt Novel set of second-order dissipative hydrodynamic equations for shear stress tensor of each component of a multi-component mixture is derived using the entropy principle [1]. Summation over the equations for all components leads to an effective relaxation-type one-component equation for the total system. In this equation the effective shear viscosity (or alternatively the η/s ratio) of the whole system is related to the partial shear pressures and cannot be considered as an external parameter. We demonstrate that in order to describe hydrodynamic behaviour of a multi-component system as a whole it is essential to solve hydrodynamic equations for each component, instead of treating a mixture as an effective one-component system with the free parameters η/s and initial time [1]. This conclusion is confirmed by comparisons of solutions of the new hydrodynamic equations with results of kinetic transport simulations, which demonstrate a very good agreement between the two approches. Thus, extractions of the η/s value of the QGP at RHIC and LHC have to be reexamined. We apply the obtained multi-component hydrodynamic equations to quantify the dissipative effects on quark and gluon spectra, which are relevant for coalescence and recombination models of hadronization. [1] A. El, I. Bouras, F. Lauciello, Z. Xu and C. Greiner arXiv:1103.4038v1 (Submitted to PRL) 116 / 269 Linear confinement and phase transitions in holographic QCD Mohammed Mia1 Charles Gale 2; Keshav Dasgupta 2; Sangyong Jeon 2 1 Columbia University 2 McGill University We study linear confinement of quarks in a class of large N gauge theories using gravity dualsthat capture the logarithmic runnings of the coupling constants in the IR and strongly coupled asymptotic conformal behavior in the UV. First we classify the most general dual gravity that describes linear confinement of quarks at zero temperature and then show that at higher temperatures, quarksmust deconfine. Using the gravity description, we also compute energy and pressure density ofthegauge theory plasma and observe a rapid change as temperature is altered, indicating a phase transition. Finally we estimate the critical temperature and discuss how to analyze phase transitions in nuclear matter using holography. 51 / 271 77 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / From RHIC to LHC: heavy quarks and J/psi in a partonic trans- port model Jan Uphoff1 Carsten Greiner 1; Oliver Fochler 1; Zhe Xu 2 1 Goethe University Frankfurt 2 Frankfurt Institute for Advanced Studies Heavy quark and J/psi production as well as their space-time evolution are studied in transport simulations of heavy-ion collisions at RHIC and LHC. In the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS) heavy quarks can be produced in initial hard parton scatterings or during the evolution of the quark-gluon plasma. Subsequently, they interact withthe medium via binary scatterings with a running coupling and a more precise Debye screening whichis derived from hard thermal loop calculations. We present results on the elliptic flow and the nuclear modification factor of heavy quarks, compare them to available data and estimate theimpactof radiative corrections quantitatively. Furthermore, results on J/psi suppression at forward and mid- rapidity are reported for central and non-central collisions. For this, we investigate cold nuclear matter effects and the dissociation as well as regeneration of J/psi in the quark-gluon plasma. 124 / 272 Percolation of Color Sources√ and the Equation of State of QGP in central Au-Au collisions at sNN =200 GeV Rolf scharenberg1 1 Purdue University The Color String Percolation Model (CSPM)[1] is used to determine√ the equation of state(EOS) of the Quark-Gluon Plasma (QGP) produced in central Au-Au collisions at sNN = 200 A GeV using STAR data at RHIC.When the initial density of interacting colored strings exceeds the 2D percolation threshold a cluster is formed, which defines the onset of color deconfinement. These interactions also produce fluctuations in the string tension which transforms the Schwinger particle (gluon) production mechanism into a maximum entropy thermal distribution analogous to QCD Hawking-Unruh radiation. The single string tension is determined by identifying the known value of the universal hadron limiting temperature Tc = 167.7 ± 2.6 MeV with the CSPM temperature at the critical percolation threshold parameter ξc =1.2. At mid-rapidity the initial Bjorken energy density and the initial temperature determine the number of degrees of freedom consistent with the formation of a ∼ 2+1 flavor QGP. An analytic expression for the equation of state, the sound velocity 2 2 Cs (ξ) is obtained in CSPM. The CSPM Cs (ξ) and the bulk thermodynamic values energy density ε/T 4 and entropy density s/T 3 are in excellent agreement in the phase transition region with recent lattice QCD simulations (LQCD) by the HotQCD Collaboration [2]. [1]. M. A. Braun, C. Pajares, Eu. Phys. J. C16, 349 (2000). [2].A. Bazavov et al., Phys. Rev. D80, 014504 (2009). Heavy Flavors / 273 78 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / √Open charm hadron measurement in pp and Au+Au collisions at s = 200 GeV in STAR Yifei Zhang1 1 Lawrence Berkeley National Lab Heavy quark production in elementary particle collisions are expected to be calculable in pQCD. In relativistic heavy ion collisions, heavy quarks are believed to be an ideal probe to study the properties of the created QCD medium. Early RHIC measurements were carried out mostly via semi-leptonic decay electrons. There are limitations in the electron approach: the charm hadron and electron kinematics are only weakly correlated due to the decay, and measured electrons have mixed contributions from various charm/bottom hadrons. Thus direct measurement of charm hadrons via hadronic decays is crucial to better understand charm-medium interactions at RHIC. In this talk, we will present the STAR preliminary results of D0 and D* in year 2009 p+p and D0 in year 2010 Au+Au collisions via hadronic decays √covering pT from 0.4 to 6 GeV/c in mid-rapidity |y|<1 at sNN = 200 GeV. Newly completed full barrel Time-Of-Flight detector was used in the analysis to improve the daughter hadron identification. The charm production pT cross section in p+p collisions will be compared with pQCD calculations. The nuclear modification factors as a function of the collision centrality willbe presented to discuss the number of binary collisions scaling of charm total cross-section. The behavior of D-meson freeze-out properties in Au+Au collisions will be compared with those of light and multi-strange hadrons. Preliminary√ results of the D0 decay vertex reconstruction in Au+Au collisions at sNN = 200 GeV from RHIC year 2007 using the silicon detectors of the STAR experiment will also be presented. 127 / 274 A High Level Online Tracking Trigger for the STAR experiment at RHIC Aihong Tang1 1 Brookhaven National Laboratory In order to utilize the high luminosity provided by RHIC and the enhanced data acquisition capability of STAR, a High Level online tracking Trigger (HLT) is being developed to effectively study the properties of the QGP created at RHIC. Based on the fast tracking and event assembling, the STAR HLT can select events of great physics interest online, which will reduce the rate to tape as well as the time of offline processing. In year 2010, the HLT has successfully selected events for J/psi elliptic flow study and anti-alpha search. It has also been used to monitor the fraction of clean collisions over background collisions during RHIC’s Beam Energy Scan program. We will present the architecture, methods and performance of the STAR HLT. Future developments on accelerating the online reconstruction of exotic decay topologies by Graphic Processing Unit will also be presented. 79 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 15 / 275 Relativistic fluid dynamics from the Boltzmann equation: going beyond the 14-moment approximation Gabriel Denicol1 Dirk Rischke 2; Etele Molnar 3; Harri Niemi 4 1 Institut fur Theoretische Physik, Goethe University, 60438 Frankfurt am Main, GermanyFrankfurt University 2 Institut fur Theoretische Physik, Goethe University, and Frankfurt Institute for Advanced Studies (FIAS), 60438 Frank- furt am Main, Germany 3 MTA-KFKI, Research Institute of Particle and Nuclear Physics, H-1525 Budapest, P.O.Box 49, Hungary 4 Frankfurt Institute for Advanced Studies (FIAS) We present a general derivation of relativistic fluid dynamics from the Boltzmann equation using the method of moments. In the 14-moment approximation [1,2], traditionally employed in the fluid- dynamical modeling of heavy-ion collisions, fluid dynamics is obtained by explicitly truncating the moment expansion of the single-particle distribution function. In contrast, in our approach all terms of the moment expansion are included and the exact equations of motion for these moments are derived. These exact equations still contain the degrees of freedom and microscopic time scales of the Boltzmann equation. We prove that in order to derive causal fluid-dynamical equations it is necessary to resolve at least the slowest microscopic time scales of the Boltzmann equation, in agreement with [3]. The truncation of the equations of motion in terms of only 14 dynamical variables is then implemented by a systematic power-counting scheme in Knudsen and Reynolds numbers, instead of the explicit truncation of the moment series, as in Israel-Stewart theory. The resulting fluid-dynamical equations and coefficients are different from the ones obtained via the 14-moment approximation and are in much better agreement with kinetic theory. This means that the fluid-dynamical description of heavy-ion collisions based on the 14-moment approximation is incomplete. [1] W. Israel and J. M. Stewart, Phys. Lett. 58 A, 213 (1976); Ann. Phys. (N.Y.) 118, 341 (1979). [2] G. S. Denicol, T. Koide, and D. H. Rischke, Phys. Rev. Lett. 105, 162501 (2010). [3] G. S. Denicol, J. Noronha, H. Niemi, and D. H. Rischke, accepted for publication in Phys. Rev. D; G. S. Denicol, H. Niemi, J. Noronha, D. H. Rischke, [arXiv:1103.2476 [hep-th]]. Theory developments / 276 Determination of relaxation times at weak and strong coupling Dirk Rischke1; Gabriel Denicol2 Harri Niemi 3; Jorge Noronha 4 1 Institut fur Theoretische Physik, Goethe University, and Frankfurt Institute for Advanced Studies (FIAS), 60438 Frank- furt am Main, Germany 2 Institut fur Theoretische Physik, Goethe University, 60438 Frankfurt am Main, Germany 3 Frankfurt Institute for Advanced Studies (FIAS), 60438 Frankfurt am Main, Germany 4 Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, SP, Brazil 80 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Using linear response theory, we derive [1] conditions for the retarded Green’s function so that the linearized equation of motion of a dissipative current is reduced to a relaxation-type equation of the Israel-Stewart type [2]. We prove that this reduction can be done, if the singularity of the retarded Green’s function closest to the origin is a simple pole on the imaginary axis. The relaxation time coefficient is then given by the location of this pole in the complex plane. This impliesthat previous attempts to derive the relaxation time from the generic long-wavelength, low-frequency (i.e., fluid-dynamical) limit of the retarded Green’s function, via an expansion in terms of gradients of the fluid-dynamical variables, in general fail to give the correct result. For a dilute gas, this prescription gives a value for the shear relaxation time that, under certain simplifying assumptions, coincides with the one derived by matching relativistic fluid dynamics to kinetic theory [3]. This shows that transient fluid dynamics is determined by the slowest microscopic and not by the fastest fluid-dynamical time scale. This has important implications for the description of the collective motion of matter formed in ultrarelativistic heavy-ion collisions, where microscopic time scales and the lifetime of the system itself can be of the same order. We also prove that the long-wavelength dynamics of the shear stress tensor in a strongly coupled N=4 SYM plasma is not described by relaxation-type equations as in Israel-Stewart theory [2]. [1] G. S. Denicol, J. Noronha, H. Niemi, and D. H. Rischke, accepted for publication in Phys. Rev. D; G. S. Denicol, H. Niemi, J. Noronha, D. H. Rischke, [arXiv:1103.2476 [hep-th]]. [2] W. Israel and J. M. Stewart, Phys. Lett. 58 A, 213 (1976); Ann. Phys. (N.Y.) 118, 341 (1979). [3] G. S. Denicol, T. Koide, and D. H. Rischke, Phys. Rev. Lett. 105, 162501 (2010). Electromagnetic probes / 277 √ Dielectron Continuum Production from sNN = 200 GeV pp and Au+Au collisions at STAR Jie Zhao1 1 SINAP/LBNL Dilepton distributions have been proposed as one of the penetrating probes for hot and dense nuclear matter created in high-energy nuclear collisions. Due to their relatively small final-state interaction cross-sections with the hot/dense environment, dileptons bring us direct information of the created matter in such collision. Since dileptons are created over all stages of heavy ion reactions, their sources vary as a function of kinematics. In the low mass region (LMR: mass<1.1GeV/c2), dilep- tons are dominated by vector mesons and directed photons, while in the intermediate mass region (IMR: 1.1< mass< 3GeV/c2) dileptons are dominated by thermal radiation of quark gluon plasma (QGP). In the high mass region (HMR: mass> 3 GeV/c2), dileptons are mostly contributed by heavy (charm and bottom) quark decays and Drell-Yan processes. As a result, the dilepton distributions, especially in the IMR and HMR, could provide new aspects of early collision dynamics in heavy ion collisions. With the completion of the full barrel time-of-flight detector, the electron identification has been significantly improved at STAR, especially in low momentum region. In√ this talk we will present the first STAR results on dielectron production in p+p and Au+Au collisions at sNN = 200 GeV. The results will be compared to hadron decay cocktails to search for vector meson in-medium mod- ifications in LMR and the QGP thermal radiation in IMR. A systematic analysis of the transverse mass distributions in IMR region as a function of the mass in Au+Au collisions will be discussed. 81 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The results will be compared to those from 200 GeV p+p collisions as well as the results fromSPS energies. Hadron thermodynamics and chemistry / 278 Observation of the antimatter helium-4 nucleus Liang Xue1 1 SINAP/BNL We present the observation of the antimatter 4He nucleus, the heaviest observed antinucleus. The identification and measurement of anti-4He relies on the mean energy loss per unit track length, the time of flight of particles, and their curvature in the magnetic field of the STAR detector. Another essential detector capability was the High Level online tracking Trigger (HLT), which helps to cope with the large data volume and greatly speeds up the search effort. 4 9 In total, 18 anti- He counts were√ detected at the STAR experiment at RHIC in 10 recorded Au+Au collisions at beam energies of sNN = 200 GeV and 62 GeV. Misidentification probability is estimated to be below 10−11. The invariant differential cross section is consistent with expectations from thermodynamic and coalescent nucleosynthesis models, which has implications for future production of even heavier antimatter nuclei, as well as for experimental searches for new phenomena in the cosmos.The yield of the stable antinucleus next in line (mass number = 6) is predicted to be down by a factor of 2.6X106 compared to anti-4He and is beyond the reach of current accelerator technology. 128 / 279 Commissioning and detector performance of the VTX-Pixel de- tector for RHIC-PHENIX experiment. Ryohji Akimoto1 1 University of Tokyo Heavy quarks (charm and bottom) is one of the key probes to study properties of Quark Gluon Plasma (QGP). A silicon vertex tracker (VTX) has been developed for RHIC-PHENIX experiment mainly for the measurement of the heavy quarks. It enables to measure tracks of charged particles precisely enough to evaluate yields of charm and bottom individually and therefore is an essential toolto study the behavior of charm and bottom inside QGP. It also can be a powerful tool for measurement of long-lived particles, such as hyperon. The VTX is a barrel detector with four layers. It consists of two silicon detectors with different readout system, inner two layers are with pixel readout and outer two layers are with strip readout. The VTX was successfully installed at the end of 2010 and started to take physics data. Inthisposter presentation, the detector performance of the pixel detector during commissioning and physics data taking is shown. Heavy flavor / 280 82 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / STAR measurements of bottom to charm ratio and heavy quark interaction with the QCD medium through non-photonic electron- hadron correlations wenqin xu1 1 University of California Los Angeles FOR THE STAR COLLABORATION Heavy Quarks are mostly produced through gluon fusions during the initial stage of the heavyion collisions. Experimentally heavy quarks are found to suffer a considerable energy loss in the QCD medium with the nuclear modification factor for non-photonic electrons (NPE) from heavy quark decays much smaller than unity in central Au+Au collisions at RHIC. To better understand the heavy flavor production and energy loss mechanism it is crucial to determine experimentally the relative contributions of Charm and Bottom meson decays to NPE and to study detailed characteristics of heavy quark interactions with the bulk QCD medium. We will present the STAR measurements of relative charm and bottom contributions to NPE from p+p collisions at 200 and 500 GeV energies. We report the total bottom quark production cross section from p+p collisions at 200 GeV extracted from NPE spectrum and B to D ratios. We will also present the NPE-hadron correlations from Au+Au collisions at 200 GeV from the 2010 RHIC run where we have collected high statistics data set with low photonic conversion background. The evolution of the NPE-hadron azimuthal angular correlation as a function of collision centralities and in comparison with that from d+Au collisions will be indicative of dynamics of heavy quark interactions with the QCD medium created in Au+Au collisions. Comparisons with theoretical calculations will also be discussed. 16 / 281 √Inclusive charged hadron elliptic flow in Au + Au collisions at sNN = 7.7, 11.5 and 39 GeV Shusu Shi1 1 the STAR collaboration We present a systematic study of the transverse momentum (pT ), rapidity√ and centrality dependence of elliptic flow, v2, using several methods in Au + Au collisions at sNN = 7.7, 11.5 and 39 GeV. The difference between v2 using event plane from detectors separated in rapidity (v2{2}) and four particle cumulants (v2{4}) seems to decrease as the beam energy decreases. The implications of this result towards understanding the energy dependence of non-flow and flow fluctuations will be discussed. The energy√ dependence of v2 will be presented√ by a comparison with results from high energies√ at RHIC ( sNN = 62.4 and 200 GeV), at LHC ( sNN = 2.76 TeV) and similar energy at SPS ( sNN = 7.6 GeV).√ We observe the v2(pT ) are very comparable (~10\%) at mid-rapidity and pT > 0.5 GeV/c beyond sNN = 39 GeV. We will also compare our results to transport model calculations, such as those from UrQMD model, AMPT default model and AMPT string-melting model with different parton cross sections. Future facilities and experiment upgrades / 282 Probing the gluonic structure of matter at a future Electron-Ion Collider Thomas Ullrich1 83 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Brookhaven National Laboratory The probing of nuclei and nucleons via deep-inelastic and diffractive processes in the high-energy (low-x) regime will open a new precision window for the investigation of the gluonic structure of matter. Studies of e+p collisions at HERA and especially d+Au collisions at RHIC have found tantalizing hints of saturated gluon densities, a phenomenon with substantial impact on the physics of heavy- ion collisions. Unveiling the collective behavior of densely packed gluons under conditions where their self-interactions dominate will require an Electron-Ion Collider (EIC): a new facility with capa- bilities well beyond those of any existing accelerator. Such a collider could be sited either at BNL or JLAB. In my talk I will outline the compelling physics case for e+A collisions with a focus on the oppor- tunities for small-x physics. I will discuss the related key measurements and give a brief status of machine concepts, detector design, and timeline. 17 / 284 √ Directed flow of Identified Particles in Au+Au Collisions at sNN = 39, 11.5 and 7.7 GeV from the STAR Experiment Yadav Pandit1 1 For the STAR Collaboration Measurements of anisotropic flow in heavy-ion collisions provide insight into the early stage of the system’s evolution. Directed flow, v1, is imparted especially early. A change of sign in the slope of dv1/dy for identified particles, particularly for protons, has been suggested as a possible signal of a first-order phase transition. In this talk, we present the STAR measurements ± ± of v1 for π , K , protons and antiprotons, as well as for all√ detected charged particles in Au + Au collisions at sNN = 39, 11.5 and 7.7 GeV as a √function of transverse momentum, rapidity and centrality. At sNN = 39 GeV, all measured v1 values follow √the trend observed at higher RHIC energies. At sNN = 11.5 and 7.7 GeV, the proton dv1/dy near midrapidity changes sign between peripheral and central collisions. This behavior is not observed for antiprotons, π± and K±. Results are compared to available model predictions. 86 / 285 Charge-to-Neutral fluctuation in AuAu collisions at Forward ra- pidity at RHIC. Prithwish (for the STAR collaboration) Tribedy1 1 Variable Energy Cyclotron Centre 84 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Event-by-event fluctuation of the ratio of multiplicities of charged and neutral particles at forward rapidity in AuAu collisions at \sqrt{s_NN}=200 GeV has been studied. As the detected charged and neutral particles are mostly from the charged pions and the decay of neutral pions respectively, this analysis addresses isospin fluctuation of pions predicted to occur for a system going through the QCD chiral phase transition [1][2]. Our study in the STAR experiment at top RHIC energy includes multiplicity measurements of charged particles and photons using the Forward Time Projection chamber (FTPC) and the Photon Multiplicity Detector (PMD) respectively. We have used νdyn;ch,γ and rm,1 as measures of dynamical fluctuation & studied their centrality dependence for data & mixed events and compared with the results from HIJNG & UrQMD. A com- parison with results for AuAu collisions at \sqrt{s_NN}=39 GeV will also be discussed to address the energy dependence of charged-to-neutral fluctuation. Ref:- [1] J.D. Bjorken, What lies ahead?, SLAC-PUB-5673, 1991. [2] J.P. Blaizot, A. Krzywicki, Phys. Rev. D 46 (1992) 246. Global and collective dynamics / 286 Viscous hydrodynamic evolution with non-boost invariant flow for the color glass condensate Akihiko Monnai1 Tetsufumi Hirano 1 1 The University of Tokyo The heavy ion program at LHC opened up a new era in the physics of the quark-gluon plasma(QGP) at higher energies. One of the most unique properties of the hot matter is the near-perfect fluidity, which was first discovered in Au-Au collisions at RHIC [1]. Relativistic hydrodynamic analyses on the momentum anisotropy of transverse collective flow revealed that small viscosity in the QGP is essential when the initial conditions are constructed from the color glass condensate (CGC), the description of saturated gluons in the nuclei before collisions. On the other hand, the dynamics of the longitudinal flow has scarcely been discussed so far due to the numerical difficulties ofthe non-boost invariant viscous hydrodynamic analyses in relativistic coordinates. Since the CGC itself is considered to be successful in reproducing the observed rapidity distributions and multiplicities at RHIC, it would be indispensable to investigate the longitudinal hydrodynamic evolution for the CGC. We develop a viscous hydrodynamic model with both shear and bulk viscosity and solve the full second-order constitutive equations [2] in the longitudinal direction with the relativistic coordinates using a novel numerical approach. The estimations are performed with the CGC-type initial distri- butions for both RHIC and LHC settings. The results exhibit visible and non-trivial deformations of the CGC rapidity distributions during the hydrodynamic stage due to the interplay between two factors: (i) Entropy production from non-equilibrium processes and (ii) entropy flux to the forward rapidity caused by non-boost invariance [3]. We find difference in the hydrodynamic effects atRHIC and LHC, which implies that readjustment of the CGC parameters might be necessary. This would be one of the possible explanations for the fact that the CGC predictions tend to underestimate the multiplicity at mid-rapidity observed in the Pb-Pb collisions at LHC experiments [4]. The results indicate that non-boost invariant hydrodynamic evolution together with viscosity is indispensable for understanding the physics of relativistic heavy ion collisions as a whole. We also obtain several important numerical insights towards a full (3+1)-dimensional viscous hydrodynamic model for the more quantitative analyses. 85 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / References: [1] http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=05-38 [2] A. Monnai and T. Hirano, Nucl. Phys A 847, 283 (2010) [3] A. Monnai and T. Hirano, arXiv:1102.5053 [nucl-th] [4] K. Aamodt et al. [The ALICE Collaboration], Phys. Rev. Lett. 105, 252301 (2010) Correlations and fluctuations / 287 Hydrokinetic predictions for femtoscopy scales in A+A collisions in the light of recent ALICE LHC results Yuriy Sinyukov1 Iurii Karpenko 2 1 Bogolyubov Institute for Theoretical Physics 2 BITP A study of energy behavior of the pion spectra and interferometry radii is carried out for the SPS, RHIC and LHC energies within the hydrokinetic approach. The main mechanisms that lead to the paradoxical, at first sight, dependence of the femtoscopy scales on a collision energy, in particular, a decrease of Rout/Rside ratio with the energy growth, are exposed. The hydrokinetic predictions for the HBT radii at the LHC energies are compared with the recent results of the ALICE experiment. The role of non-equilibrium stage of the matter evolution in the formation of femtoscopy scalesat the LHC energies is analyzed. The results are based on: 1. Iu.A. Karpenkov, Yu.M. Sinyukov. Energy dependence of pion interferometry scales in ultra- relativistic heavy ion collisions. Phys. Lett. B 688 50 (2010). 2. Yu.M. Sinyukov, Iu.A. Karpenkov. Hydrokinetic predictions for femtoscopy scales in A+A colli- sions in the light of recent ALICE LHC results. arXiv:1103.5632v1 [nucl-th] 29 Mar 2011. 3. Very new results based on the Hybrid Hydrokinetic Model (not published yet). 18 / 288 Mach Cones and Two-Particle Correlations: The Origins in a Ki- netic Transport Approach Ioannis Bouras1 Andrej El 1; Carsten Greiner 1; Felix Reining 1; Francesco Lauciello 1; Harri Niemi 2; Oliver Fochler 1; Zhe Xu 2 1 University of Frankfurt 2 FIAS Frankfurt In a microscopic transport model we investigate evolution of conical structures using different source terms. Development of a strong collective behavior near the ideal hydro limit is visible, resulting in formation of Mach Cones. In addition, for the first time the transition from ideal to viscous Mach Cones is demonstrated. We investigate dependence of the Mach Cone angle in different scenarios of energy depositions into the medium. The numerical results on two-particle correlations are compared to an analytical approximation. 86 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / In our simulations we find that a double-peak structure, as observed in experiments at RHIC, cannot be explained/created by propagation of a high-energy jet. 125 / 289 Shear Viscosity of the QGP in Central A-A Collisions at RHIC and LHC Energies in the Color String Percolation Approach Brijesh Kumar Srivastava1 1 Department of Physics-Purdue University-Unknown The high-energy heavy ion collisions at RHIC energies have shown evidence of a new state ofmatter with very low viscosity to entropy density ratio η/s similar to that of a nearly ideal fluid. The η/s is obtained for the QGP with in the context√ of the Color String Percolation Model√ (CSPM) using data produced in Au-Au collisions at sNN = 200 A GeV at RHIC and Pb-Pb at sNN = 2.76 TeV at LHC [1]. The relativistic kinetic theory relation for η/s is evaluated using CSPM values for the temperature and the mean free path of the QGP constituents [2]. The experimental transverse momentum spectrum√ is used to measure the percolation density pa- rameter ξ in Au-Au collisions (STAR)[3]. For Pb-Pb at sNN = 2.76 TeV, ξ values are obtained from the extrapolation at RHIC energy. The value of η/s is 0.184 and 0.278 at the CSPM initial temper- ature of 193.6 MeV (RHIC) and 262.2 MeV (LHC), respectively. These values are 2.3 and 3.5 times the AdS/CFT conjectured lower bound 1/4π. We compare the CSPM η/s(T /Tc) analytic expression with weak coupling (wQGP) and strong coupling (sQGP) calculations. This indicates that the QGP is a strongly coupled fluid in the phase transition region. [1] M. A. Braun, C. Pajares, Eu. Phys. J. C16, 349 (2000). [2] T. Hirano, M. Gyulassy, Nucl. Phys. A769, 71 (2006). [3] R. P. Scharenberg, B. K. Srivastava and A. S. Hirsch, Eur. Phys. J. C71, 1510 (2011). 101 / 290 Finite lifetime effects on the photon production from a quark- gluon plasma Frank Michler1 Björn Schenke 2; Carsten Greiner 1 1 University of Frankfurt 2 Brookhaven National Laboratory Direct photons play an important role as electromagnetic probes from a quark-gluon plasma (QGP) created in heavy-ion collisions. After being once produced, they leave the medium undisturbed an thus provide direct insight into the early stage of the collision. We use the real time Keldysh formalism to investigate how non-equilibrium effects such as a finite lifetime modify the resulting photon spectra. We provide an ansatz which eliminates the divergent contribution from the vacuum polarization and renders the photon spectrum UV-finite if the time evolution of the QGP is described in a suitable manner. 87 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 19 / 291 √ Elliptic Flow of charged particles in Au+Au collisions at sNN = 7.7, 11.5 and 39 GeV from STAR Michael K. Mitrovski1 1 for the STAR collaboration The study of elliptic flow and non-flow effects over a wide energy range can provide information on the onset of collective effects in√ heavy-ion collisions. In 2010, STAR collected high statistics data samples at lower RHIC energies at sNN = 7.7, 11.5 and 39 GeV. We will present measurements of charged particle elliptic flow using the event-plane (v2{EP }) determined from detectors separated in eta, 2-particle (v2{2}) and 4-particle (v2{4}) correlation methods integrated over pt and η along with differential elliptic flow v2(pt) and v2(η). The difference using v2{EP }, v2{2} and v2{4} decreases with decreasing the beam energy. In addition we observe that no large differences√ (∼10\%) are visible for the pt dependence (| η | < 1.0 and pt > 0.5) of v2{4} starting from sNN = 39 GeV. A 2 2 change of the energy dependence is observed in the difference between v2{2} and v2{4} which is related to v2 fluctuations (σv2 ) and non-flow correlations (δ2). The measurements will be compared to measurements at SPS, higher RHIC and LHC energies, as well as string hadronic/partonic and hydrodynamic model calculations. 102 / 292 Low-mass meson production√ through di-leptonic decays in p+p and Au+Au collisions at sNN = 200 GeV from STAR Bingchu Huang1 1 STAR BNL Ultra-relativistic heavy ion collisions provide a unique environment to study the properties of strongly- coupled Quark Gluon Plasma (sQGP) at high temperature and high energy density. Oneofthe 2 crucial probes to study the sQGP is the di-electron production in the low (Mll < 1.0GeV /c ) and the intermediate (1.0 < M_{ll}<3 GeV/c^{2})massregion.Intheintermediatemassregion, thedi − electronproductionaredirectlyrelatedtothermalradiationofthesQGP.Inthelowmassrange, wecanstudytheproductionofvectormesonsinthemedium, whereanymodificationsobservedmayrelatetothepossibilityofchiralsymmetryrestoration.T henewlyinstalledST ARBarrelT ime− of−F lightdetector(TOF )provideshighacceptanceandefficiencyforchargedparticleidentificationatmid− rapidity.Bycombiningthetime−of−flightfromtheT OF andtheenergylossfromT imeP rojectionChamber, ST ARisabletoidentifyelectronwithhighpurityfromlowtointermediatetransversemomentumatmid− rapidity.Inthistalk, wepresentthemeasurementsofvectormeson\omegainvariantyieldsviadi− electrondecaysin200GeV p+pandAu+Aucollisionsandthedi−electroncontinuumspectrumin200GeV p+ pcollisionsatmid−rapidity.T heperspectiveonpossiblecomparisonsbetween\rho\righarrow e^{+} e^{-}and\rho\righarrow pi^{+} pi^{-}andlimitson\eta\rightarrow e+e-$ will be discussed. Theory developments / 293 Chirality, magnetic field and parity violation in hot QCD mat- ter Dmitri Kharzeev1 1 Stony Brook and BNL 88 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / An overview of the recent progress in understanding the interplay of quantum anomalies, chirality, and magnetic field in the dynamics of QCD fluid will be presented. The current theoretical description of the chiral magnetic and chiral vortical effects within anomalous magnetohydrodynamics will be described. It allows a quantitative approach to these phenomena in heavy ion collisions, and the first results from such studies will be reviewed. The existing and future experimental measurements needed to establish or refute the local violation of parity in hot QCD matter will be discussed. 103 / 295 Leptonic decay of phi(1020) meson measured with the STAR ex- periment Christina Markert1 1 University of Texas at Austin Hadronic resonances can play a pivotal role in providing experimental evidence for partial chiral symmetry restoration in the deconfined quark-gluon phase produced at RHIC and the LHC. Their lifetimes, which are comparable to the lifetime of the fireball, make them a valuable tool to study medium modifications to the resonant state due to the chiral phase transition signatures of mass shifts and/or width broadenings. This canbe done via the leptonic decay of resonances, however hadronic regeneration of resonances feeds into this signature as well. We will present the measurement of phi(1020) at mid-rapidity in p+p collisions and the preliminary results of the resonance signal in Au+Au collisions at 200 GeV using the STAR upgrade Time of Flight detector for electron identification. 142 / 296 Finite-size scaling search for the critical endpoint of QCD in heavy ion data Eduardo Fraga1 Leticia Palhares 2; Paul Sorensen 3 1 Universidade Federal do Rio de Janeiro 2 Institut de Physique Theorique, CEA/Saclay 3 Brookhaven National Laboratory Given the short lifetime and the reduced volume of the quark-gluon plasma (QGP) formed in high- energy heavy ion collisions, a possible critical endpoint (CEP) will be blurred over a region and the effects from criticality severely smoothened. Nevertheless, the non-monotonic behavior of correla- tion functions near criticality for systems of different sizes, given by different centralities inheavy ion collisions, must obey finite-size scaling. We apply the predicting power of scaling plots tothe search for the CEP of strong interactions in heavy ion collisions using data from RHIC and SPS. 89 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The results of our data analysis suggest that a critical point cannot be below chemical potentials µ ∼ 450 MeV. Extrapolating the analysis, we speculate that criticality could appear slightly above µ ∼ 500 MeV. Using available data we extrapolate our scaling curves to predict the behavior of new data at lower center-of-mass energy, currently being investigated in the Beam Energy Scan program at RHIC. Energy scan / 297 Identified hadron production from the RHIC beam energy scan program in the STAR experiment lokesh kumar1 1 Kent State University A current focus at RHIC is the Beam Energy Scan (BES) program to study the QCD phase diagram — temperature (T ) vs. baryon chemical potential (µB). The BES program aims to verify some predic- tions from QCD: that a cross-over occurs at µB = 0, and that there exists a first-order phase transition at large µB and a critical point at an intermediate µB. The spectra and ratios of produced particles can be used to extract T and µB in different energies and system sizes. √The Solenoidal Tracker At RHIC (STAR) experiment has collected data for Au+Au collisions at sNN = 7.7 GeV, 11.5 GeV, and 39 GeV in year 2010. One of the advantages during the BES pro- gram was the enhanced particle identification with availability of full Time-Of-Flight detector. In addition, STAR collected Cu+Cu collisions at 22.4 GeV in year 2005. We present mid-rapidity spectra (pT or mT − m0), rapidity density, average transverse mass, and particle ratios for identified hadrons from the STAR experiment. The centrality and transverse momentum dependence of the particle yields and ratios will be compared to existing data at lower and higher beam energies and to various transport models like AMPT and UrQMD. Collision dynamics are stud- ied systematically in the framework of chemical and kinetic freeze-out and their properties extracted from the particle ratios and spectra. 76 / 298 Multiparticle system in high energy hadronic/nuclear collision and matter state of early universe R. Klippert1; Shi-Yuan Li2; V. A. De Lorenci1 1 UNIFEI 2 SDU The universe is expanding, hence in early times it was more dense than it is today. Thespacetime curvature becomes arbitrarily large around the singular point, leaving room for arbitrarily large en- ergetic processes as well as arbitrarily dense matter states to take place. The matter states ofthe largest densities that human being can produce and study microscopically in laboratory are those generated in high energy collisions. The matter state appearing just after the inelastic hadronic/nuclear collisions is taken as the dominant matter-energy content of the universe. Working on the central rapidity plateau, a nonsingular and anisotropic toy-model presenting an inflationary phase that naturally evolves to a decelerated expansion can be obtained. Moreover, by considering the specific state of the glasma fluid at small time scales, 90 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / an solution describing the evolution of the spacetime is presented. These simple examples of the collider physics motivated cosmology show that the multiparticle sys- tem produced in collision can shed light on the matter state of early universe. 20 / 299 Viscous relaxation time in relativistic hydrodynamics Xu-Guang Huang1 Dirk Rischke 1 1 Institute for Theoretical Physics Relativistic Navier-Stokes hydrodynamics is acausal and unstable. These problems are solved by introducing relaxation times into the constitutive equations of the viscous tensors. We derive the microscopic formulae of the shear and bulk viscous relaxation times by using the projection oper- ator method. In the leading-order of perturbative calculation, we find the ratios of the viscosities and corresponding relaxations times are purely thermodynamic functions and independent of the scattering details. Energy scan / 300 Energy dependence of the freeze out eccentricity from azimuthal dependence of HBT at STAR Christopher Anson1 1 The Ohio State University Non-central heavy ion collisions at RHIC create an anisotropic participant zone of QCD matter under extreme conditions of energy and matter density. While this zone is initially out-of-plane-extended, pressure gradients cause the hot, dense medium to expand preferentially in plane. Over time, this expansion makes the shape more spherical, perhaps even becoming extended in the in-plane direc- tion. The change in shape is determined by the expansion and freeze-out time scales which depend, in part, on the early pressure gradients. As a result, the freeze-out shape may provide a sensitive probe of the Equation of State of hot QCD matter. The recent RHIC Beam Energy Scan at \protect $\sqrt{s_{NN}}$ of 7.7, 11.5, and 39 GeV provides an opportunity to explore the energy dependence of the freeze out eccentricity. The new low energy data from STAR complements high statistics data sets at \protect $\sqrt{s_{NN}}$ of 62.4 and 200 GeV. The dependence of the HBT radius parameters on azimuthal angle relative to the reaction plane have been extracted. These dependences can be related to the freeze out eccentricity within the context of a blast wave model. We will present STAR's most recent results on azimuthally-dependent HBT across a wide range of energies. 52 / 301 D0 meson production in pp collisions at the LHC with ALICE and prospects for charm flow measurements in PbPb collisions Chiara Bianchin1 1 Universita degli Studi di Padova-Universita & INFN, Padova-Unkn 91 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The ALICE experiment at LHC studies p-p and Pb-Pb collisions with the aim of investigating the properties of the high-density state of strongly-interacting matter, expected to be produced in Pb-Pb collisions. D mesons are powerful probes of the medium since the charm quark is produced in a very short time scale and experiences all the evolution of the collision. The measurement of the azimuthal anisotropy of D mesons production in PbPb semi-peripheral collisions is one of the goals of the heavy flavour physics program because directly related to the heavy quark elliptic flow. The measurement of open charm production in p-p collisions, besides providing a reference forthe study of nuclear effects in Pb-Pb collisions, is very interesting per se, as a test of perturbative QCD predictions at the high energy frontier. The ALICE detector is well suited to accomplish these measurements thanks to the precise vertex reconstruction, tracking and PID capabilities. In this poster the preliminary results on the D^0 production cross section in pp collisions, obtained by the D^0->Kpi channel, will be presented and the prospects for the measurement of the elliptic flow will be described. 53 / 302 Phenomenological interpolation of inclusive J/psi production to proton-proton collisions at sqrt(s)=2.76 TeV and 5.5 TeV Alessandro De Falco1; Francesco Bossù2; Ginés Martínez García3; Martino Gagliardi4; Smbat Grigoryan5; Zaida Conesa del Valle6 1 Università and Sezione INFN di Cagliari, Cagliari, Italy 2 Università degli Studi and Sezione INFN di Torino, Torino, Italy 3 Subatech, Ecole des Mines de Nantes, Université de Nantes, CNRS-IN2P3, Nantes, France 4 Sezione INFN di Torino, Torino, Italy 5 JINR, Dubna, Russia and YerPhI, Yerevan, Armenia 6 European organization for Nuclear Research (CERN), Genève, Switzerland J/psi production is one of the key measurements in heavy-ion collisions at the LHC. It is expected to provide means to discriminate between different scenarii, ranging from full suppression by colour screening to enhancement by charm quark pair recombination. In 2010, the LHC delivered Pb-Pb collisions at the center of mass energy per nucleon pair of 2.76 TeV. The knowledge of the J/psi cross section in p-p collisions at the same energy is crucial foracorrect interpretation of the data. We perform an interpolation of the inclusive J/psi cross section to p-p collisions at sqrt(s)=2.76 TeV (and sqrt(s)=5.5 TeV), based on the available experimental data. First, we describe the energy dependence of the J/psi cross section at mid-rapidity. Second, we study the rapidity dependence of J/psi production and provide estimates for the cross section in the forward rapidity regions of interest for the LHC experiments. Third, we develop the tools to extrapolate the transverse momentum distributions. In our approach, we adopt both phenomenological and pQCD-driven techniques and, where possible, we combine them. Our study is documented in arXiv:1103.2394 [nucl-ex]; it is meant to be complementary and provide an useful cross-check to the measurements performed during the recent p-p data-taking campaign at sqrt(s)=2.76 TeV at the LHC. 92 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Electromagnetic probes / 303 Direct photons at low transverse momentum – a QGP signal in pp collisions at LHC Fuming Liu1 Klaus Werner 2 1 Huazhong Normal University 2 Subatech We predict that direct photon production in pp collisions at 7~TeV will get at least 10 times enhanced compared to the next to leading order pQCD predictions, at low transverse momentum ( pt lesssim 10~GeV/c), due to the thermal photon emissions from a quark gluon plasma (QGP) formed in high multiplicity events. Thus the enhancement of direct photon production at low pt can be a QGP signal in pp collisions. Electromagnetic probes / 304 Exploring compressed nuclear matter with HADES Piotr Salabura1 1 IFUJ [email protected], [email protected] In the energy domain of 1-2 GeV kinetic energy per nucleon, HADES has been performed systematic studies of electron-positron production in C+C, Ar+KCl, p+p, d+p and p+Nb collisions. Our results demonstrate that electron pair emission in small collision systems, such as C+C, can essentially be explained as a superposition of independent N+N collisions with a dominant contribution from the p-n channel. The comparison of the N+N reference spectrum with the di-electron invariant-mass distribution measured in Ar+KC collisions shows a pronounced excess radiation. The properties of the excess as a function of the transverse mass are quantified. Further medium effects have been investigated in p+Nb interactions at 3.5 GeV by a direct compari- son to p+p reactions measured at the same energy. Differential dielectron production cross sections have been extracted and can be compared in detail in the pi^{0}, eta and the vector meson regions. The results will be discussed and compared to the ones obtained in photo-induced reactions. Intriguing results were also obtained from the reconstruction of hadrons with open and hidden strangeness in Ar+KCl collisions. While the measured abundance of all reconstructed particles are well described assuming thermalization, the also reconstructed double-strange baryon Xi^{-} appears about ten times more abundant than expected. Also, the phi/omega ratio is much larger than the one measured in N-N collisions and does not require any OZI suppression. Further investigations of compressed nuclear matter by means of di-electrons as penetrating probes and strangeness production will be followed up over the forthcoming years with an upgraded HADES detector in Au+Au and Ag+Ag collisions. 93 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 87 / 305 Dynamics near QCD critical point by dynamic renormalization group Yuki Minami1 1 Japan We study the critical dynamics near QCD critical point (CP) by dynamic renormalization group (RG). As a basic equation for the critical dynamics, we construct the nonlinear Langevin equation, which is a standard dynamic equation for a CP in condensed matter physics. Our onstruction is based on the generalized Langevin equetion and the relativistic hydrodynamics. Applying the dynamic RG to the constructed equation, we derive the RG equation for the transport coefficients and obtain their critical exponents. We find that the resulting RG equation turns out to be the same as that for the liquid-gas CP, alhough the Langevin equations for the two critical points are different. Therefore, the bulk viscosity and the thermal conductivity strongly diverge at theQCDCP. We also show that the thermal and viscous diffusion modes exhibit critical slowing down. In contrast, the sound mode shows critical speeding up. Reference Y.Minami arXiv:1102.5485 [hep-ph] 143 / 306 QCD Phase Diagram based on Strong Coupling Lattice QCD Takashi Nakano1 Akira Ohnishi 2; Kohtaroh Miura 3 1 Kyoto University 2 Yukawa Institute for Theoretical Physics 3 INFN-Laboratori Nazionali di Frascati In RHIC and FAIR experiments, it is important to search the position of the critical point and first- order phase boundary in QCD phase diagram. Strong Coupling Lattice QCD has been applied to investigate the chiral phase transition at finite temperature and chemical potential. We take account of the chiral and deconfinement phase transitions in the strong coupling lattice QCD, and investigate the QCD phase diagram. In this study, the calculated critical temperature at zero chemical potential almost reproduces the results of Monte Carlo simulations in the strong coupling region. By comparison, in the finite chemical potential region, Polyakov loop effects reduce the critical point temperature and the first order chiral phase transition line shrinks. 94 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Global and collective dynamics / 310 Sensitivity of the elliptic flow coefficient to a temperature-dependent shear viscosity-to-entropy density ratio in ultrarelativistic heavy- ion collisions at RHIC and LHC Harri Niemi1 Dirk Rischke 2; Etele Molnár 3; Gabriel Denicol 4; Pasi Huovinen 4 1 Frankfurt Institute for Advanced Studies 2 Frankfurt Institute for Advanced Studies; Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität 3 Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität; MTA-KFKI, Research Institute of Particle and Nuclear Physics 4 Institute für Theoretische Physik, Johann Wolfgang Goethe-Universität We investigate the effects of a temperature-dependent shear viscosity-to-entropy density ratio η/s on the elliptic flow of hadrons in ultrarelativistic heavy-ion collisions [1]. We use relativistic dissipative fluid dynamics to model the space-time evolution of the hot and dense system formed in such collisions. The final hadron spectra are calculated using the Cooper-Frye freeze-out procedure. By studying different parametrizations for the temperature dependence of η/s, we found that√ the viscous suppression of the elliptic flow coefficient in sNN = 200 GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) is dominated by the viscosity in the hadronic phase and in the phase transition region. However, the elliptic flow at RHIC is largely insensitive to the viscosity of the quark-gluon plasma (QGP). On the other hand, we found that sensitivity of the elliptic flow to the high-temperature η/s increases with increasing multiplicity and simultaneously the sensitivity to the hadronic viscosity decreases. At the highest LHC energy, the elliptic flow becomes sensitive to the QGP viscosity and insensitive to the hadronic viscosity. The change of the sensitivity from hadronic to QGP viscosity from RHIC to LHC can provide access to determining the temperature dependence of η/s from elliptic flow data. [1] H. Niemi, G. S. Denicol, P. Huovinen, E. Molnar, D. H. Rischke, [arXiv:1101.2442 [nucl-th]]. 144 / 311 Chiral transition in a magnetic field and at finite baryon den- sity Jens O.Andersen1 Rashid Khan 1 1 Norwegian University of Science and Technology 95 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / We study the quark-meson model with two quark flavors in a strong external magnetic field at finite temperature and finite baryon chemical potential.We calculate the full renormalized effective potential to one loop order in perturbation theory.While the critical temperature in the chiral limit is almost unchanged and compared to the case with zero external magnetic field, the transition is becoming more strongly first order. 16 / 312 Suppression of large transverse momentum hadrons in central Pb+Pb collision at LHC Subrata Pal1 1 Tata Institute of Fundamental Research, Mumbai, India Quenching of high transverse momentum hadrons formed in Pb+Pb collisions at the center-of-mass energy of 2.76 TeV is studied within A MultiPhase Transport (AMPT) model. The initial conditions for quark and gluon jet production are obtained from the recently updated HIJING 2.0 model that invokes the latest parton distribution function as well as an energy dependent cut off momentum parameter p_0 for jet production in the two-component model. Once the parameters of the model has been fixed by reproducing the measured charged particle spectra in p+p collisions attheLHC energy regime, we shall demonstrate that the centrality dependence of charged particle multiplic- ity in Pb+Pb collisions is mostly controlled by the gluon shadowing at small transverse momentum. We shall show within the AMPT model that simultaneous reproduction of the measured centrality dependence of charged hadrons and the quenching of high transverse momentum hadrons, quanti- fied by the nuclear modification factor R_{AA}, could further constrain the parton-parton scattering cross section to a rather small value at the LHC energy. Global and collective dynamics / 313 Turbulent fluctuations around Bjorken flow Stefan Floerchinger1 Urs Achim Wiedemann 1 1 CERN For large Reynolds number (which is inverse to viscosity), fluids are known to develop turbulence. Therefore, the phenomenological evidence for a small viscosity suggests that the hydrodynamical description of heavy ion collisions may have a turbulent regime. Assuming that averaged velocities are described by Bjorkens model, we investigate local fluctuations around it. These perturbations are governed by non-linear equations and we characterize classes of qualitatively different evolution in terms of Reynolds numbers. Perturbations at different rapidities are found to decouple quickly, and the local evolution becomes effectively two-dimensional. The resulting Navier-Stokes equation of non-relativistic form (obtained after suitable coordinate transformations) can be discussed within the theory of Kolmogorov and Kraichnan. In particular, unlike three-dimensional turbulent flow, two-dimensional viscous fluid dynamics can show the interesting phenomenon of inverse cascading of energy into large scale structures. We speculate on possible phenomenological implications of these findings. 96 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Jets / 314 Medium-induced modifications of color flow in high transverse momentum processes Andrea Beraudo1; José Guilherme Milhano2; Urs Wiedemann3 1 Centro Studi e ricerche ”Enrico Fermi” - Rome (Italy) 2 Advanced Research Fellow and Invited Professor , CENTRA-IST (Lisbon) and Scientific Associate, CERN-PH-TH 3 CERN-PH-TH Heavy ion collisions at both RHIC and the LHC show strong medium-induced modifications of high- pT single inclusive hadron spectra, jet-like particle correlations and reconstructed jets. A dynamical understanding of these jet quenching phenomena is typically sought within a partonic picture in which the energy of highly energetic parent partons is degraded due to multiple inelastic and/or elastic interactions inside QCD matter. In the current model implementations of this parton energy loss the hadronization process is unaf- fected by it on account that for sufficiently energetic projectiles time dilation should guarantee their hadronization outside the medium. However, as it has been pointed out before, the interaction of a colored parton with a QCD medium modifies the color flow of the parton shower and arguably can imprint on the hadronization process at much higher transverse momentum than estimated previously. In this context, we present here the first QCD-based calculation of medium-induced color flow. Decomposing the multiple scattering diagrams of the BDMPS-Z formalism for parton energy loss into color-singlet ‘prehadronic’ systems, we observe that (in comparison to vacuum fragmentation) medium-induced effects do not only degrade the longitudinal momentum of these color-singlet systems butalso strongly enhance their invariant mass. The larger the invariant mass of a color-singlet at theendof the perturbative evolution, the more likely it is for such system to decay into a larger number of hadronic fragments and thus leave a smaller fraction of the total available energy to the leading hadron. Therefore, for multi-partonic states that show the same kinematic distributions at the endofthe perturbative evolution, medium-modified color flow can be a significant additional source of medium-induced multiplicity increase and medium-induced degradation of the leading hadron. We illustrate this general observation in simple models. We also identify a color flow specific forma- tion time argument that indicates that effects of color-flow induced additional suppression can persist over transverse energies up to tens of GeV, and may contribute to an enhanced slope of the nuclear modification factor. 145 / 316 Probing deconfinement with chiral effective models at imaginary chemical potential Kenji Morita1 Bengt Friman 2; Krzysztof Redlich 3; Vladimir Skokov 2 1 Kyot University 2 GSI 3 University of Wroclaw The sign problem in lattice QCD prevents us from directly evaluating thermodynamics at real quark chemical potential since the Dirac determinant takes complex value. At imaginary chemical potential, this quantity 97 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / becomes real thus Monte-Carlo simulation is possible. One needs an analytic continuation to relate a quantity obtained at imaginary chemical potential to a real one. Some characteristic features, however, have been found also at the imaginary chemical potential as realization of the symmetries possessed by QCD. Therefore, the imaginary chemical potential provides us additional information on the rich phase structure of QCD. In this work, we investigate the phase structure of Polyakov loop-extended chiral effective models at imaginary chemical potential with a particular emphasis on the confinement-deconfinement transition. First we discuss the phase transitions in the PNJL and PQM models for different implementations of the Polyakov loop potential, within the mean field approximation. We find a critical endpoint of the deconfinement transition at imaginary chemical potential, of which origin is shown to nicely illustrate interplay between the chiral transition and the deconfinement. Second, we discuss how to characterize the deconfinement transition by utilizing the imaginary chemical potential in analogy with the so-called dual order parameter. Finally, we discuss the effect of the quantum fluctuation on the determination of the phase diagram in the PQMmodel by making use of the functional renormalization group approach. 54 / 317 Charmonium mass in hot and dense hadronic matter from QCD sum rules Kenji Morita1 Su Houng Lee 2 1 Kyot University 2 Yonsei University Charmonia in medium provide us information on the change of the confinement property induced by the medium. We have developed an approach based on QCD sum rule which connects temperature dependent QCD condensates to the spectral function through the operator product expansion of the current correlation function. The leading contribution to the OPE is the dimension four gluon condensate which suddenly drops in the vicinity of the deconfinement transition temperature therefore can be regarded as an effective order parameter. We showed that this behavior is related to the corresponding change of the spectral property of the charmonia and is consistent with lattice QCD measurement of the imaginary time correlators. In this work, we further extend our prescription to utilize more realistic gluon condensates measured by lattice QCD with physical quark masses. By making use of the resonance gas model, we determine the gluon condensates at nonzero baryonic chemical potential and explore the charmonia at temperature and chemical potential which are accesible with current and future experiments. We show that the reduction of the charmonium mass will lead to change of particle ratio in the statistical hadronization scenario. Correlations and fluctuations / 318 98 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Determining initial state fluctuations from flow measurements Jean-Yves Ollitrault1 Matthew Luzum 2; Rajeev Bhalerao 3 1 SPhT, Saclay 2 IPhT Saclay 3 TIFR, Mumbai Long-range azimuthal correlations are generated by fluctuations of the initial energy distribution, followed by collective flow. We list eight independent observables which can be measured using multiparticle azimuthal correlations in the first three Fourier harmonics. Some of these observables are already well known, such as v2{2} and v2{4}, but most of them are new, in particular, the joint correlations between v1, v2 and v3. We show that by taking ratios of these observables, one can construct quantities which are largely independent of the hydrodynamic response of the medium, and thus are solely determined by initial fluctuations. We present predictions for these ratios using a Monte-Carlo Glauber model and a Monte-Carlo KLN model, and compare to existing data from STAR and ALICE. 88 / 319 Understanding initial state fluctuations Rajeev Bhalerao1 Jean-Yves Ollitrault 2; Matthew Luzum 2 1 TIFR (Tata Inst. of Fundamental Research) 2 IPhT (CEA/Saclay) In event-by-event hydrodynamics, the initial distribution of participants in the azimuthal plane fluc- tuates from event to event. We study the dipole asymmetry ϵ1, eccentricity ϵ2, and triangularity ϵ3, as a function of centrality, both analytically as well as numerically. These Fourier harmonics of the initial-state geometry have been shown to largely determine the flow coefficients v1, v2, and v3, re- spectively, in hydrodynamic calculations, and so are of significant theoretical interest. We consider fluctuations in the centre-of-mass of the participant distribution to order 6. In an independent-source model, we derive expressions for ϵ3{2}, ϵ3{4}, ϵ1{2}, and various correlations among the orienta- tion angles ψ1, ψ3 and ψ2 ≡ ΨPP which is the participant-plane angle. We compare these analytic results with numerical results based on Monte-Carlo Glauber and Monte-Carlo KLN models. We find that the independent-source model explains many of the features seen in the Monte-Carlo models, and thus can provide insight into the fluctuations seen in heavy-ion collisions. 55 / 322 Ratio of J/Psi to Rho Photoproduction Cross Sections at the Rel- ativistic Heavy Ion Collider with STAR Janet Seger1 99 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Creighton University The intense electromagnetic fields associated with relativistic heavy ions make a heavy-ion collider a unique tool to study two-photon and photonuclear interactions. In this talk, we present a new measurement of J/psi photoproduction in 200 GeV AuAu collisions at RHIC. The pT distribution of the J/psi mesons peaks at very low pT, consistent with expectations for coherent photoproduction. Both the photoproduction cross section and the J/psi rapidity distribution are expected to show the effects of gluon shadowing. We present a measurement of the ratio of J/psi to rho^0 mesoncross sections in 200 GeV AuAu collisions, as well as a distribution of rapidity within |y| < 1 for the J/psi mesons. The measured results are compared to theoretical models. Jets / 324 Jet-Hadron Correlations in STAR Alice Ohlson1 1 Yale University In recent years, the study of dihadron correlations has been one of the primary methods used to investigate the propagation and modification of hard-scattered partons in the QGP. Due to recent ad- vancements in jet-finding algorithms it is now possible to use reconstructed jets in these correlation studies. This increases the kinematic reach of such analyses and improves the signal-to-background ratio. We show results of a systematic study of jet-hadron correlations in 200 GeV central Au+Au colli- sions, which are indicative of a broadening and softening of jets which interact with the medium. Furthermore, jet-hadron correlations suggest that the suppression of the associated hadron yield at high-pT is balanced by low-pT enhancement. 21 / 326 Bulk viscosity in heavy-ion collision Kevin Dusling1 1 North Carolina State University In this work we examine the bulk viscous correction to the distribution function (δf) in both the re- laxation time approximation and from weakly coupled QCD. We then incorporate this bulk viscous correction in 2+1 Dimensional viscous relativistic hydrodynamics and compute particle spectra and elliptic flow. Since the thermal mass for quark and gluons are different the departures from equilib- rium are also different. We explore how a species dependent bulk viscous δf affects particle spectra and how the bulk and shear viscous effects can possibly be separated in the data. QCD Phase diagram / 327 Lattice QCD based equation of state at finite baryon density 100 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Pasi Huovinen1 1 Johann Wolfgang Goethe-Universität The effects of non-zero baryon density are expected to become important in hydrodynamic modeling of heavy collisions below the highest energy at RHIC. Recent calculations in effective models and in QCD using Dyson Schwinger equation suggest that the transition inQCD remains a crossover up to baryon chemical potentials of about 800MeV [1]. If so, the equation of state relevant for hydrodynamic models can be calculated on the lattice using Taylor expansion. However, there are large cutoff effects in present lattice calculations for non-zero chemical potentials. We employ the lattice QCD data on Taylor expansion coefficients [2] to extend our previous parametriza- tion of the equation of state [3] to finite baryon density. When we take into account lattice spacing and quark mass dependence of the hadron masses [3], the Taylor coefficients at low temperature are equal to those of hadron resonance gas. Therefore we require require that the equation of state is smoothly connected to the hadron resonance gas equation of state at low temperatures. Some preliminary results were reported in [4]. We also show how the hydrodynamical evolution is affected by this equation of state in the energy range relevant for SPS and the RHIC energy scan. [1] T.K. Herbst et al, Phys. Lett. B696 (2011); C.S. Fischer et al, arXiv:1104.1564 [2] M. Cheng et al, Phys. Rev. D79 (2009) 074505; C Miao and C. Schmidt,PoS LATTICE2008 (2008) 172 [3] P.Huovinen and P.Petreczky, Nucl.Phys. A837 (2010) 26 [4] P.Huovinen and P.Petreczky, J. Phys. Conf. Ser. 230 (2010) 012012 56 / 328 D0 production in p+p sqrts = 200 GeV collisions at STAR David Tlusty1 1 NPI ASCR The charm production is sensitive to early dynamics of the created system in RHIC heavy ion collisions. Dominant process of charm quark production at RHIC is believed to be initial gluon fusion which can be calculated in the perturbative QCD. Understanding both the charm production total cross section and the fragmentation in p+p collisions is a baseline to further explore the QCD medium via open charm and charmonium in heavy ion collisions. This poster will present the reconstruction of open charm meson D0 via the weak decay to K and π mesons in the p+p collisions at midrapidity for sqrts = 200 GeV. The analysis is based on the large p+p minimum bias sample collected in RHIC year 2009 by the STAR detector. The Time-Of-Flight detector, which covered 72% of the whole barrel in year 2009, was firstly used to improve the decay daughter identification. The open charm cross section from hadronic decay channel will be presented. 101 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / QCD Phase diagram / 330 Transition temperature and the equation of state from lattice QCD, Wuppertal-Budapest results Zoltan Fodor1 Antal Jakovac 2; Christian Holbling 1; Gergely Endrodi 3; Kalman Szabo 1; Sandor Katz 4; Stefan Krieg 1; Szabolcs Borsanyi 1 1 BUW 2 Budapest Technical University 3 University of Regensburg 4 ELTE The QCD transition is studied on lattices up to Nt=16. The strange susceptibility the chiralconden- sate and the renormalized Polyakov loops are presented. The equation of state is determined on lattice with Nt-6,8,10 and at some temperature values with Nt=12. The pressure, the trace anomaly, the energy and entropy density and the speed of sound are presented as functions of the temperature in the range 100 …1000 MeV . We give estimates for the pion mass dependence and for the contri- bution of the charm quark. We compare our data to the equation of state obtained by the “hotQCD” collaboration. 89 / 332 Forward-Backward Multiplicity Correlations for Identified Parti- cles at STAR Michael Skoby1 1 Purdue University Long-Range Forward-Backward multiplicity correlations(LRC) may be a signal for multiple partonic interactions in dense matter, whereas short-range correlations are due to independent sources [1,2]. Previously, strong LRC have been measured at STAR in 200 GeV central Au+Au collisions, and were shown to decrease with decreasing centrality [3]. The Color Glass Condensate model, which de- scribes sources as longitudinal flux tubes, predicts that the correlation will grow with centrality [4,5]. Furthermore, fluctuations in the number of gluons at early times will produce alongrange correlation significantly larger for pions than protons [5]. We present the forward-backward corre- lation of identified hadrons (pions, kaons, protons) as a function of rapidity for Au+Au collisions at sqrt(s_NN) = 200 GeV. The particle identification is carried out by measuring their average energy loss intheSTAR Time Projection Chamber. The centrality dependence of the correlation strength will also bedis- cussed for each particle species. References: [1] A. Capella and A. Krzywicki, Phys. Rev. D 18, 4120 (1978). [2] A. Capella et al., Phys. Rep. 236, 225 (1994). [3] B. I. Abelev et al. (STAR Collaboration), Phys. Rev. Lett. 103, 172301 (2009). [4] Y. V. Kovchegov, E. Levin, and L. McLerran, Phys. Rev. C 63, 024903 (2001). 102 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / [5] N. Armesto, L. McLerran, and C. Pajares, Nucl. Phys. A 781, 201 (2007). Global and collective dynamics / 333 Elliptic and triangular flow in the event-by-event 3+1D viscous hydrodynamics Sangyong Jeon1 Bjoern Schenke 2; Charles Gale 1 1 McGill University 2 Brookhaven National Lab I will present results for elliptic and triangular flow coefficients v2 and v3 in Au+Au collisions at sqrt(s) = 200A GeV using event-by-event 3+1D viscous hydrodynamic simulations. I will report on the effect of initial state fluctuations and finite viscosities on the flow coefficients v2andv3as functions of transverse momentum and pseudo-rapidity. I will argue that simultaneous measurements of v2 and v3 can determine the shear viscosity-entropy ratio more precisely. I will also touch upon recent calculations of v2 and v3 for the LHC heavy ion collisions. Pre-equilibrium and initial state / 334 Spectrum of initial fluctuations in the little bang Raju Venugopalan1 Francois Gelis 2; Kevin Dusling 3 1 Brookhaven National Laboratory 2 CEA, Saclay 3 North Carolina State Univ. We discuss an ab initio computation of the initial spectrum of fluctuations in the pre-equilibrium Glasma formed in heavy ion collisions [1]. Our result resums to all loop orders the leading unstable quantum fluctuations at early times. We showed explicitly previously for a scalar field theory [2]that averaging over the analogous spectrum of initial fluctuations leads to hydrodynamic behavior. The computation can now be carried out for QCD and we outline the algorithm for doing so. In addition to providing a mechanism for early thermalization, our result for the small fluctuation spectrum also enables one to compute a) key features of jet modification at early times and b) sphaleron transition rates in the Glasma. An understanding of the latter is crucial for the charge separation mechanism in the Chiral Magnetic Effect. We relate our weak coupling albeit non-perturbative results to strong coupling approaches to thermalization. References: [1] K. Dusling, F. Gelis and R. Venugopalan, manuscript in preparation. [2] K. Dusling, T. Epelbaum, F. Gelis and R. Venugopalan, Nucl. Phys. A850:69 (2011). 103 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 129 / 335 The STAR Upgrade Program Lijuan Ruan1 1 Brookhaven National Laboratory The STAR detector at RHIC collected its first events in June of 2000. The detector has beenupgraded several times since that time and we are continuing to upgrade the system in order to enhance the capabilities of the detector and widen the scope of the research program. In this talk, we will discuss the ongoing upgrades that will conclude in the period between 2011 and 2015. The list of topics includes a detector upgrade that will enhance the pointing near the vertex for heavy flavor identification (the Heavy Flavor Tracker (HFT)), a mid-rapidity detector at large radius to enhance particle ID in the lepton sector (the Muon Telescope Detector (MTD)), and detectors in the forward direction to enable W boson identification and asymmetry measurements (the Forward Gem Tracker (FGT)) aswell to measure spin asymmetries (the Forward Hadron Calorimeter(FHC)). A high level trigger upgrade (HLT) that allows us to make fast online trigger decisions for rare events will also be discussed. After describing the overall upgrade program, we will focus on the MTD and the HLT in order to review their progress, and first results, in more detail. 90 / 336 Local baryon-strangeness correlation from hypernuclei and coa- lescence volume from light nuclei in relativistic heavy ion colli- sions Song Zhang1 Jinhui Chen 1; Yu-Gang Ma 1 1 Shanghai Institute of Applied Physics, CAS, China The production of hypertriton and light nuclei are simulated in a dynamical coalescence modelcou- pled with a multi-phase transport model (AMPT)~\cite{SZhang10}. The beam energy dependence of 3 3 × Λ strangeness population factor, S3 = ΛH/( He p ), is calculated to study local baryon-strangeness correlation as a valuable tool to probe the nature of the dense matter created in relativistic heavy ion collisions. We find that AMPT with string melting predicts an increase of S3 with increasing beam energy, and is consistent with experimental data, while AMPT with only hadronic scattering results in a low S3 throughout the energy range from AGS to RHIC, and fails to describe the ex- perimental data. And we analyzed coalescence parameters, B2 and B3, based on the production of deuteron, helium-3 and proton. The coalescence parameters of B2 and B3 decrease with increas- ing of beam energy or number of participant. The value of B2 and B3 in this model are consistent with the measurement by experiment collaboration in nucleus-nucleus collisions at different beam energy~\cite{NA49-07} or in different centralities~\cite{STAR09}. The freeze-out correlation volume, 1−A Vf (A is atomic number), is calculated in AMPT model. The results of coalescence parameter ∝ 1−A and the freeze-out correlation volume follow the relation of BA Vf , which is from coalescence mechanism and observed in experiments~\cite{BAVf,STAR09,HLiu06}. This beam energy and sys- tem size dependences indicate the increase of source size in more high energy collisions and in more central collisions. References \bibitem{SZhang10} S. Zhang, J. H. Chen, H. Crawford et~al., {Phys. Lett. B} {\bf 684}, {224} ({2010}). \bibitem{NA49-07} V. L. Kolesnikov (for NA59 Collaboration), {J. Phys. Conf. Ser.} {\bf 110}, {032010} 104 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / (2008) and references therein. \bibitem{STAR09} B. I. Abelev et~al. (STAR Collaboration), arXiv:0909.0566. \bibitem{BAVf} H. H. Gutbrod et~al., {Phys. Rev. Lett.} {\bf 37}, {667} ({1976}) \bibitem{HLiu06} H. Liu and Z. Xu, arxiv:nucl-ex/0610035. 126 / 338 Spectrum of fermion coupled with massive vector boson at finite temperature in gauge invariant formalism Daisuke Satow1 Teiji Kunihiro 2; Yoshimasa Hidaka 3 1 Kyoto university 2 Kyoto University 3 RIKEN [email protected], [email protected] We investigate the massless fermion spectral function coupled with a massive vector boson (mass: m) in the whole region of temperature (T) [1]. The massive vector boson is described as aU(1) gauge boson so that we can analyze the extremely high-T region where T/m ≫ 0, in contrast to the Proca formalism [2]. We show that a novel peak appears in the fermion spectral function for T~m in addition to the two peaks corresponding to the normal fermionic and anti-plasmino excitations obtained in the m=0 case [3]. We find that the novel peak seems to persist though with a small strength even for T≫m, where the other two peaks remains robust and are smoothly connected to those obtained in the HTL approximation. Since our model has a U(1) gauge invariance, the poles of the fermion propagator must be gauge invariant. We have confirmed the gauge invariance of the poles forT≪m and T~m, while the gauge invariance of the poles are satisfied only for a restricted region of the gauge-fixing parameter for T≫m. We explicitly obtained the adequate region of the gauge-fixing parameter for T≫m. Our results shows that the unitary gauge, which corresponds to the large gauge-fixing parameter limit, is found to be inadequate for the calculation of the fermion propagator in the T≫m region, although the unitary gauge is often adopted in the literature. The relevant physical systems of our analysis include the quark-gluon plasma phase near thephase transition temperature (T_c) since vector-type collective excitation may exist there and its mass may become very small (T≫m) just above T_c. The neutrino spectrum in the early universe is also relevant since the neutrino couples with the massive vector particles, W and Z boson. The present work tells us that the analysis of the neutrino spectral function in the unitary gauge or in the Proca formalism [4] can suffer from a strong gauge dependence in theT≫m region. References [1] D. Satow, Y. Hidaka and T. Kunihiro, Phys. Rev. D 83,045017 (2011). [2] M. Kitazawa, T. Kunihiro and Y. Nemoto, Prog. Theor. Phys. 117, 103 (2007). [3] H. Weldon, Phys. Rev. D 26, 2789 (1982). [4] D. Boyanovsky, Phys. Rev. D 72 033004 (2005). 339 Centrality dependence of viscous quark gluon plasma at LHC Asis Chaudhuri1 105 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Bikash Sinha 1 1 Variable Energy Cyclotron Centre [email protected] √ Extensive analysis of RHIC data at sNN =200 GeV Au+Au collisions has provided convincing ev- idence that Quark Gluon Plasma (QGP) produced in such a collision behaves almost like aperfect fluid with viscosity per specific enropy η/s is around the lower bound as per AdS/CFT η/s = 1/4π. Recently, ALICE collaboration has come out with the data for elliptic√ flow as a function of pT as well as the centrality dependence of charged particle multiplicity in sNN =2.76 TeV Pb+Pb collision [1]. Curiously enough ALICE data for charged particles can be explained by using almost the same value of η/s ≈ 0.08 as in RHIC, except for very central collision where the data favors ideal fluid η/s ≈0 rather than a viscous fluid, although energy√ of collision at LHC is substantially higher thanRHIC energy and expected to go up still further to sNN =5.5 TeV. It is also expected, in general, that η/s should go up for QGP as a function of temperature [2]. For RHIC, it is also expected that the hadron system is more relevant than QGP, whereas, for LHC QGP viscosity should be more important than the hadronic system [3]. So, it is quite natural to ask the question why η/s for RHIC remain rather similar to LHC, around η/s ≈0.08. We investigate this issue and came to the inevitable conclusion that this similarity is forced upon us by the dynamics related to the geometry of the collision. For central collision or near about a value of initial time of τi ≈=0.2 fm and a temperature of 700 MeV is quite reasonable. However, taking into account peripheral collision (70-80%) one can not escape from τi ≈ 0.6 fm with initial temperature 3 of 500 MeV. Please note that even for τi=0.6 fm the fitted energy density remains at ~126 GeV /fm , a factor of 3.5 larger than required for RHIV energy collision. The role of peripheral collision has been overlooked by for and large; it is interesting to notethatit is the peripheral collision which precipitates recent LHC data to behave rather closely to RHIC data. We need to know η/s as a function of temperature to pin point the location of phase√ transition or rapid cross over from hadronic to quark gluon plasma. Data even at a higher energu sNN =5 TeV especially for photon and dilepton results will facilitate this idea. [1] K. Aamodt et al, Phys. Rev. Lett. 106, 032301 (2011), arXiv:1011.3914 [nucl-ex]. [2]L. P. Csernai, J. I. Kapusta and L. D. McLarren, Phys. Rev. Lett.97,152303 (1997). [3] H. Niemi, G. S. Denicol, P. Huovinen, E. Molnar, D. Rischke, arXiv:1101.2442 [nucl-th]. Correlations and fluctuations / 340 √ Dynamical K/π, p/π, and K/p fluctuations in sNN = 7.7-200 GeV Au+Au collisions Terence Tarnowsky1 1 Michigan State University Terence J Tarnowsky (for the STAR Collaboration) Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. Results from new measurements of dynamical K/π, p/π, and K/p ratio fluctuations are presented. The commencing of a QCD critical point search atRHIC has extended the reach of possible measurements of dynamical K/π, p/π, and K/p ratio fluctuations from Au+Au collisions to lower energies. The STAR experiment has performed a comprehensive√ study of the energy dependence ofthese dynamical fluctuations in Au+Au collisions at the energies sNN = 7.7, 11.5, 39, 62.4, and 200 GeV. New results are compared to previous measurements and to theoretical predictions from several models. The measured dynamical K/pi fluctuations are found to be independent of collision energy, 106 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / while dynamical p/π and K/p fluctuations have a negative value that increases toward zero attop RHIC energy. Correlations and fluctuations / 342 Correlations and fluctuations from lattice QCD Claudia Ratti1; Kalman Szabo2; Sandor Katz3; Stefan Krieg2; Szabolcs Borsanyi2; Zoltan Fodor2 1 Torino University 2 Wuppertal University 3 Eotvos University Budapest We present the new results of the Wuppertal-Budapest lattice QCD collaboration on flavor diagonal and non-diagonal quark number susceptibilities with 2+1 staggered quark flavors, in a temperature regime between 120 and 500 MeV. A Symanzik improved gauge and a stout-link improved staggered fermion action is utilized; the light and strange quark masses are set to their physical values. Lattices with N_t=6,8,10,12 are used. 57 / 343 J/Psi production in proton-proton collisions at sqrt(s) = 2.76 TeV in the ALICE Forward Muon Spectrometer Claudio Geuna1 1 IRFU-cea - Centre d’Etudes de Saclay Claudio Geuna, CEA Saclay Irfu/SPhN Gif-sur-Yvette, 25 March 2011 on behalf of the ALICE collaboration Abstract The ALICE experiment at LHC has collected, in March 2011, proton-proton data at sqrt(s) =2.76TeV. This energy in the center of mass allows to have a pp reference for the PbPb collisions thathave been collected, at the end of 2010, at sqrt(sNN) = 2.76 TeV. In this poster, we show the first analysis, performed on the pp data sample at sqrt(s) =2.76TeV, concerning the detection of the J/ψ meson through its decay into μ+μ− pairs at forward rapidity ( 2.5 < y < 4 ) in the ALICE Muon Spectrometer. We focus on the different steps required to obtain the integrated and differential cross-section for inclusive J/ψ production, the latter one as a function of the J/ψ transverse momentum pT and rapidity y. First of all, details are provided concerning the criteria adopted to select runs and events used for the analysis. The different tecniques used for the extraction of the signal are discussed aswellthe method followed to determine the acceptance and efficiency corrections. Finally, we show some preliminary plots providing also some details about the alignment of the tracking chambers of the Muon Spectrometer. 344 107 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Inhomogeneous phase during the chiral transition Toshitaka Tatsumi1 1 Kyoto U. Recently there have been many works about the inhomogeneous phases accompanying the chiral transition, which should have implications on relativistic heavy-ion collisions as well as compact- star phenomena [1]. Among them we here concentrate on the emergence and properties of a special one called dual- chiral-density wave (DCDW) state, which enjoys interesting features such as parity-violating phase, liquid-crystalline structure and spin-density wave [2]. In particular, the one-dimensional order is quasi-long-range-order in this case such that the correlation functions of scalar and pseudoscalar densities decay algebraically, as in the smectic liquid crystal[3]: fluctuations in the DCDW phase exhibit the heterogeneous dispersion relation. The symmetry breaking pattern is also characteristic in this phase transition: U(1) subgroup ofchi- ral symmetry and one-dimensional translational symmetry are broken at the same time, but is still invariant under the specific combination of them. So, Nambu-Goldstone modes (phasons) should ex- hibit a hybrid features of phonons and “pions”. Moreover, magnetization spatially modulates to pre- tend a spin density wave, which may be related with the magnetic activity of compact stars. After briefly introducing DCDW in the chiral limit and discussing its salient features, weelucidate the physical mechanism of its emergence; we emphasize differences from the usual Overhauser ef- fect or the nesting effect of the Fermi surface. Then we present a formalism to deform the original DCDW, to include the symmetry breaking ef- fect [4]. Taking a variational method we show that the deformed DCDW can be described by a topological object: it is realized by embedding the chain of the sine-Gordon kinks in 1 + 1 dimen- sion into 1 + 3 dimensional quark matter [5]. Thus we can generalize DCDW without losingthe basic concepts. Finally we briefly discuss the neutrino emission process by way of beta decay of quarks intheDCDW phase, as a definite example of implications of DCDW on compact-star phenomena [6]. [1] D. Nickel, Phys. Rev. Lett. 103 (2009) 072301; Phys. Rev. D80 (2009) 074025. S. Carignano, D. Nickel and M Bubballa, arXiv:1007.1397. [2] T. Tatsumi and E. Nakano, hep-ph/0408294. E. Nakano and T. Tatsumi, Phys. Rev. D71 (2005) 114006. [3] G. Baym et al., Nucl. Phys. B210 (1982) 193. [4] T. Maruyama, E. Nakano and T. Tatsumi, “Ferromagnetism: Theory, Materials and Uses”, Nova Pub., NY, (2011) in press. [5] V. Schoen and M. Thies, Phys. Rev. D62(2000) 096002. [6] T. Muto and T. Tatsumi, in preparation. Global and collective dynamics / 345 Spectra, flow and HBT in PbPb collisons at the LHC Piotr Bozek1 1 IFJ PAN Krakow/ Rzeszow University √ The expansion of the fireball created in Pb-Pb collisions at s = 2.76TeV is modelled using the rel- ativistic viscous hydrodynamics. The experimentally observed interferometry radii are well repro- duced. The recent data of the ALICE Collaboration on the elliptic flow as function of the centrality can be very well described using the hydrodynamic expansion of a fluid with a small shear viscosity 108 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / η/s = 0.08. The elliptic flow as function of the transverse momentum shows systematic devia- tions from a hydrodynamic behavior in the small momenta region p⊥ < 800MeV. It indicates that a non-negligible contribution of non-thermalized particles from jet fragmentation is present. Jets / 346 Jet quenching and elliptic flow in heavy ion collisions at RHIC and LHC within a pQCD-based partonic transport model Oliver Fochler1 Carsten Greiner 1; Zhe Xu 2 1 Institut für Theoretische Physik, Goethe-Universität Frankfurt 2 Frankfurt Institute for Advanced Studies We present fully dynamic simulations of heavy ion collisions at RHIC and at LHC energies within the perturbative QCD-based partonic transport model BAMPS (Boltzmann Approach to Multi-Parton Scatterings). We focus on the simultaneous investigation of high-pT observables, such as jet quench- ing, and bulk observables, such as the elliptic flow. The model features inelastic 2 <-> 3 processes based on the Gunion-Bertsch matrix element and has recently been extended to include light quark degrees of freedom. This allows for direct comparison to hadronic data on the nuclear modifica- tion factor via a fragmentation scheme for high-pT partons and also allows for the discussion of elliptic flow results in terms of a quark recombination picture. We present results on the nuclear modification factor of neutral pions at different centralities for Au+Au collisions at RHIC energies and compare to experimental data. First results on the nuclear modification of charged hadrons in central Pb+Pb collisions at the LHC are also presented and compared to recent ALICE data. Fur- thermore the differential elliptic flow of gluons and quarks as well as the centrality dependence of the integrated elliptic flow is studied within the same framework for Au+Au at RHIC and Pb+Pbat LHC. 91 / 347 Charge balance correlations and contributions to local parity vi- olation observables Sören Schlichting1 Scott Pratt 2 1 Technische Universität Darmstadt 2 Michigan State University We study charged particle correlations in a thermal freeze-out model with local charge conservation. By comparison to STAR data we find that balancing charges are emitted from significantly smaller rapidity regions in central collisions compared to peripheral collisions. The results indicate that charge diffusion is small and the centrality dependence points to a change of the charge production mechanism. We also calculate the contributions from charge-balance correlations to STAR’s local parity violation observable. We show how local charge conservation, when combined with elliptic flow, explains much of STAR’s measurement. In addition we show how momentum conservation ,when combined with elliptic flow, induces charged particle correlations contributing to the STAR measurement. 109 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 146 / 348 Mix-ratios of Higher Order Moments of Proton and Kaon as a baseline of QCD Critical Point search at RHIC Lizhu Chen1 1 CCNU/BNL One of the main goals of the RHIC Beam Energy Scan program is to search for the QCD critical point (CP) in the QCD phase diagram. Non-monotonic dependence of the ratios of the various moments of conserved (such as net-charge and net-baryon) number distributions with beam energy has been considered to be a signal for the CP. In addition to this, it has been recently proposed that a certain set of mix-ratios of these moments can be measured to validate the occurrence of critical phenomena. These ratios are constructed so as not to have any dependence on model parameters, including the correlation length. Their values after subtracting the statistical contribution should remain asunity even in presence of CP. Measurements of these mix-ratios are a vital step towards establishing a complete set of observables for the critical point program at RHIC. In this poster, we will present the preliminary results of these mix-ratios using event-by-event proton and kaon multiplicity at mid- √rapidity measured in Au+Au collisions at sNN = 7.7, 11.5, 39 and 200 GeV by the STAR experiment at RHIC. It has been observed that most of these mix-ratios are unity as a function of either the beam energy or the collision centrality. 58 / 349 Centrality dependence of muon tracking efficiency in the ALICE Forward Muon Spectrometer for Pb-Pb collisions at 2.76 TeV. Antoine Lardeux1 1 SUBATECH, on behalf of the ALICE collaboration The study of the J/ψ production and open heavy flavors in central Pb-Pb collisions is apromising tool to probe the properties of QGP in ALICE experiment at LHC. To conduct this experimental study, it is necessary to know well the response fonction of the de- tectors used, in particular, the forward muon spectrometer to detect quarkonium and heavy flavour in their muonic channel. In this sense, the tracking efficiency integrated on the five stations ofthe spectrometer is a critical variable. Indeed, for cross-section calculations we have to apply a correc- tion factor Acc∗ε. We use, for to evaluate this factor, realistic Monte Carlo simulations run by run. In heavy ions collisions, one of the main parameters is the centrality of the collision, directly related to the multiplicity and the occupancy of the detector. It is therefore crucial to know the centrality dependence of muon tracking efficiency. Another aspect of J/ψ study is to obtain its contribution to the single muon spectrum. Simulations using J/ψ measured cross-section, pt and y distributions, allow to obtain this contribution. Similar evaluation will be done for the vector meson in order to get rid of the resonance contribution to the single muon spectrum. Global and collective dynamics / 350 Event-by-event hydrodynamics and elliptic flow from fluctuat- ing initial state 110 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Hannu Holopainen1 Harri Niemi 2; Kari J. Eskola 1 1 University of Jyväskylä 2 Frankfurt Institute for Advanced Studies We develop a framework for event-by-event ideal hydrodynamics to study the differential elliptic flow which is measured at different centralities in Au+Au collisions at Relativistic Heavy IonCol- lider (RHIC). Fluctuating initial energy density profiles, which here are the event-by-event analogues of the eWN profiles, are created using a Monte Carlo Glauber model. Using the same event plane method for obtaining v2 as in the data analysis, we can reproduce both the measured centrality de- pendence and the pT shape of charged-particle elliptic flow up to pT ∼ 2~GeV. We also consider the relation of elliptic flow to the initial state eccentricity using different reference planes, anddis- cuss the correlation between the physical event plane and the initial participant plane. Our results demonstrate that event-by-event hydrodynamics with initial state fluctuations must be accounted for before a meaningful lower limit for viscosity can be obtained from elliptic flow data. 92 / 352 Strongly intensive measures for chemical fluctuations in A+A and p+p collisions: statistical and transport models. Viktor Begun1 1 Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine The chemical fluctuations may indicate a presence and determine the position of the critical point on a phase diagram of the QCD matter. This inspired energy and system size scan program of NA61 collaboration at the SPS CERN and low energy scan program of STAR collaboration at the RHIC BNL. However, many other effects – fluctuations of the number of nucleon participants in A+A collisions, effects of global conservation laws, and the change in the detector acceptance with energy – may hide or produce the fluctuation signals. All these effects are discussed in the present talk within statistical and transport models. Recently, the strongly intensive measures of chemical fluctuations which are independent of volume and volume fluctuations were proposed. We calculate these strongly intensive quantities for pions, kaons, and protons produced in A+A collisions at SPS and RHIC energies in statistical models. The results for different statistical models within grand canonical, canonical and micro-canonical ensembles are compared with the HSD transport model calculations in p+p and A+A collisions. We also present the HSD model predictions for the future measurements of strongly intensive quantities in p+p collisions by NA61 collaboration within their detector acceptances. Pre-equilibrium and initial state / 353 AAMQS: a non-linear QCD description of new HERA data at small- x Paloma Quiroga Arias1 Carlos Salgado 2; Guilherme Milhano 3; Javier Albacete 4; Nestor Armesto 2 1 LPTHE , UPMC Univ. Paris 6 2 Departamento de Fisica de Particulas and IGFAE, Universidade de Santiago de Compostela 3 CENTRA, IST Lisbon and CERN TH 111 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 4 Institut de Physique Theorique, CEA/Saclay Recent developments in the computation of the NLO improvement for non-linear QCD evolution equations has allowed, for the first time, for the consistent description of experimental data usinga first principle approach. In particular, the Balitsky-Kovchegov equation including running coupling effects (rcBK) has been shown to provide an excellent global description of inclusive DISdata. I will present a global analysis of available data on inclusive structure functions measured in electron- proton scattering at small values of Bjorken-x, including the latest data from the combined HERA analysis on reduced cross sections. The resulting parametrizations allow for the reliable computation of physical observables in a kinematical region (relevant for both p-p and A-A programmes at the LHC) where the standard DGLAP based techniques are expected to fail. Also, the inclusion of the heavy quark contribution has resulted in a good description of the experimental data for the charm component of the proton structure function. Further, I will discuss the kinematical domain where significant deviations from NLO-DGLAP should be expected and a strategy to interface this approach, reliant on k_t factorization, with the commonly used collinearly factorized parton distribution functions. Also preliminary extensions for nuclei will be discussed. Heavy flavors / 354 Heavy quarkonium measurements from PHENIX Abhisek Sen1 1 Georgia State University Quarkonia suppression is one of the highly cited signature of quark gluon plasma (QGP) formed in relativistic heavy ion collisions. PHENIX observed a√ high suppression of J/Ψ production in Au+Au collisions at s = 200 GeV. However, theoretical predictions remain diverse due to lack of precise knowledge of heavy flavor meson production, suppression, regeneration in hot and dense medium and other cold nuclear effects. In order to separate these effects the PHENIX collaboration√ also measured J/Ψ production in d+Au collisions at s = 200 GeV for isolating√ cold nuclear effects and Au+Au collisions at low energies ( s = 62 GeV and 39 GeV) to study the onset of nuclear phase transition to QGP. The idea being that the critical energy density for a crossover into the QGP phase may not be reached for certain combinations. The measurement of J/Ψ nuclear modification factors at different center of mass energies may elucidate this transition and supplement our understanding of the energy dependence of cold nuclear matter effects. \\ In this talk, we will show the latest results of J/Ψ and√ Upsilon measurements from p+p, d+Au collisions at s = 200 GeV and several energy scans of Au+Au collisions. Theory developments / 355 Jet modification from RHIC to LHC Abhijit Majumder1 112 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Chun Shen 1 1 The Ohio State University We calculate the modification of hard jets in dense extended matter inthe higher-twist formalism. The single gluon emission spectrum from a hard quark due to multiple scattering in a medium is evaluated as a power series in inverse powers of the virtuality of thehardjet. Retaining corrections up to next to leading power, we calculate the medium modified fragmentation function by resumming the effect of multiple gluon emissions in a virtuality ordered DGLAPlike evolution equation. This new formalism is applied to the computation ofthe RAA in high-energy heavy-ion collisions at RHIC and LHC. The medium is modeled using viscous 2+1D fluid dynamics which has been tuned to describe both the spectra and the v2 at a pT < 2 GeV. The sole parameter of the calculation qˆ is set proportional to the entropy density and is found to be approximately 2 GeV2/fm at a plasma temperature of T = 350 MeV. Using this we obtain a satisfactory description of the centrality and transverse momentum dependence of the RAA at RHIC as well as its dependence on the azimuthal angle. With no change in parameters we obtain a natural description of the rising RAA as measured by the ALICE collaboration at the LHC. Some new results from a Monte-Carlo routine based on this formalism will also be presented. 22 / 356 Polarization Effects at RHIC and LHC Celso Barros1 1 Universidade Federal de Santa Catarina Recently, the STAR collaboration has measured the Λ and anti-Λ polarizations in 200 GeV Au-Au collisions [1]. These results can be understood in terms of a model [2], that we proposed recently, based on the hydrodynamical model, and taking into account the effect of the final-state interac- tions (that occur in the hadronic phase) between the hyperons and other produced particles. These final interactions are described in terms of chiral effective lagrangians, that consider many hadronic processes. This model describes quite well the antihyperon polarization data obtained in proton- nucleus collisions, and now we extended it to study nucleus-nucleus collisions, with a very good accord. Theoretical results obtained with other models will also be discussed. The perspectives of hyperon and antihyperon polarization at LHC is another subject of interest. References: [1] STAR Collaboration: B. I. Abelev et al., Phys. Rev. C, 76, (2007) 024915. [2] C. C. Barros Jr. and Y. Hama, Phys. Lett. B., 699, 74 (2011). Jets / 359 Jet Quenching via Jet Collimation Jorge Casalderrey Solana1; José Guilherme Milhano2; Urs Wiedemann1 1 CERN PH-TH 2 Instituto Superior Tecnico (IST) and CERN PH-TH 113 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The ATLAS and CMS Collaborations recently reported strong modifications of dijet properties in heavy ion collisions. In this work, we discuss the extent to which these first data constrain the mi- croscopic mechanism underlying jet quenching. Simple kinematic arguments lead us to identify a frequency collimation mechanism via which the medium efficiently trims away the soft components of the jet parton shower. Through this mechanism, the observed dijet asymmetry can be accomo- dated with values of qˆ L that lie in the expected order of magnitude. Electromagnetic probes / 361 Can transport peak explain the low-mass enhancement of dilep- tons at RHIC? Yukinao Akamatsu1 Hideki Hamagaki 2; Tetsufumi Hirano 3; Tetsuo Hatsuda 2 1 Nagoya University 2 University of Tokyo 3 Sophia University We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant D and the relaxation time \tau. The observed low-mass enhancement sets a lower-bound on the diffusion constant, D>2/T, with T being temperature. To reach this lower bound, we start with the second-order relativistic dissipative hydrodynamics by Israel and Stewart. The linearized hydrodynamic equation in external electromagnetic field gives a spectral function which is parametrized by D and \tau. Combining the spectral function with the full 3D hydrodynamic evolution, theoretical dielectron spectra and the experimental data are compared. Detailed analysis shows that the low-mass dilepton enhancement originates mainly from the high- temperature QGP phase where there is a large electric charge fluctuation as obtained from lattice QCD simulations. 93 / 362 Higher moments of Net Kaon Fluctuation in the Beam Energy Scan of STAR AMAL SARKAR1 1 iit-bombay The Relativistic Heavy-Ion Collider (RHIC), at BNL, has started its beam energy scan programto locate the QCD critical point which is also one of the main aims of the STAR experiment. Calculations on the lattice predict that the higher moments of the multiplicity distribution ofthe conserved quantities like the net-charge, net-baryon, net-strangeness are related to the correspond- ing susceptibilities and the correlation length of the system. These moments shows deviation from monotonic behavior at critical point. STAR experiment has already published the result for higher moments of the net-proton multiplicity distribution in Au+Au collisions at √sNN = 19.6, 62.4 and 200 GeV. 114 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Here we report the first measurements of the standard deviation, skewness and kurtosis ofthenet kaon fluctuation measured by the STAR detector at mid-rapidity for Au+Au collisions atvarious energies. It will be compared with various theoretical models. 147 / 363 QCD thermodynamics by numerical simulations of Lattice QCD with Wilson-type quarks Shinji Ejiri1 1 Niigata University We report results on thermodynamic properties of the quark matter obtained by numerical simula- tions of lattice QCD with dynamical Wilson-type quarks. So far, most of the lattice QCD studiesat finite temperature and chemical potential have been performed using staggered-type quark actions with the fourth-root trick for the quark determinant. To control and estimate systematic errors due to lattice discretization, it is indispensable to carry out simulations adopting different lattice quark actions, e.g. the Wilson-type quark action. In this talk, we discuss the following topics performing simulations with the Iwasaki improved gauge action and the clover improved Wilson quark action: (1) The Equation of state computed by afixed scale approach and a comparison with previous results by staggered quark actions. (2) The scaling properties around the chiral phase transition point. Assuming the scaling function is the same as the O(4) spin model, we determine the phase transition line in the temperature and chemical potential plane. (3) The quark mass dependence of the nature of the QCD transition through the histogram of physical quantity. 148 / 364 Signals from the QCD phase transition in the early universe Juergen Schaffner-Bielich1 Simon Schettler 1; Tillmann Boeckel 1 1 Heidelberg University The QCD phase diagram might exhibit a first order phase transition for large baryochemical potentials. We explore the cosmological implications of such a QCD phase transition in the early universe. We propose that the large baryon-asymmetry is diluted by a little inflation where the universe is trapped in a false vacuum stateof QCD. The little inflation period will change the freeze-out criteria for WIMP dark matter so that their annihilation and production cross section would be reduced by orders of magnitude. In addition the power spectrum of cold dark matter can be affected up to mass scales of globular clusters. The effects of the QCD phase transition onthe relic gravitational wave spectrum is controlled by the trace anomaly of QCD where we apply recent data from lattice gauge calculations. The QCD transition imprints a strong step into the spectrum of gravitational waves depending on the strength of the QCD phase transition which could be detected with the gravitational wave 115 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / detectors LISA, BBO and by pulsar timing. The little QCD inflation scenario could be probed with the low-energy run at BNL’s RHIC, at the heavy-ion program at GSI’s FAIR, and also at CERN’s LHC as it changes the freeze-out criteria for WIMP dark matter. References: Boeckel and Schaffner-Bielich, Phys. Rev. Lett. 105 (2010) 041301 Schettler, Boeckel, Schaffner-Bielich, Phys. Rev. D83 (2011) 064030 Future facilities and experiment upgrades / 365 Heavy ion program at JINR NICA/MPD facility Alexander Sorin1 Alexander Kovalenko 1; Grigory Trubnikov 1; Igor Meshkov 1; Richard Lednicky 1; Vladimir Kekelidze 1 1 Joint Institute for Nuclear Research New project NICA/MPD (Nuclotron-based Ion Collider fAcility/MultiPurpose Detector) is now un- der realization phase at JINR (Dubna). The main goal of the project is to start in the coming years an experimental study of hot and dense strongly interacting matter and search for possible signs of the mixed phase and critical endpoint in heavy ion collisions. This study should be carried outat centre-of-mass ion collision energies of √sNN = 4-11 GeV (NN-equivalent) and at average luminos- ity of 10E27 cm-2 s-1 for Au (79+). The program also foresees start-up of fixed target experiments with the extracted beams from upgraded JINR synchrotron Nuclotron at energies up to 5.81 GeV/u (scaled to A/Z = 2) and intensity up to 5*10E8 s-1 (for Au 79+). Another goal of the project is aimed to study the spin structure of nucleon and the other spin sensitive phenomena with colliding beams of polarized protons and deuterons. The SPD (Spin Physics Detector) setup aimed at that purpose is under design. Heavy flavors / 366 J/Psi production and correlation in p+p and R_{AA} at high-pt in Au+Au collisions Zebo Tang1 1 University of Science and Technology of China The cc¯ bound state J/ψ provides a unique tool to probe the properties of the hot dense medium produced in heavy-ion collisions, but to date its production mechanism is not understood clearly either in heavy-ion collisions or in hadron hadron collisions. Measurement of J/ψ production at high pT is particularly interesting since at high pT the various models give different predictions. Besides, high pT particles are widely used to study the parton-medium interactions in heavy-ion collisions. The previous high-pT J/ψ measurements in p+p and Cu+Cu collisions at RHIC published by the STAR collaboration found several interesting things, though constrained by limited statistics and system size. + − In this talk, we will present the new measurement of J/ψ → e e production at large pT range (0 < pT < 10 GeV/c) at mid-rapidity (|y| < 1)in p+p and Au+Au collisions at 200 GeV. The datasets are from RHIC year 2009 p + p and 2010 Au+Au runs with significantly reduced material, the newly 116 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / installed full TOF, and high data acquisition rates. J/ψ pT spectra and nuclear modification factors from low to high pT will be discussed to understand its production mechanism and medium modifica- tions. The J/ψ-hadron azimuthal angle correlation in p+p collisions will be presented to disentangle B-mesons contributions to inclusive J/ψ and study J/ψ hadronization mechanism. 117 / 368 Hadron Productions at LHC Energies with HIJING2.0 Model Wei-Tian Deng1 Rong Xu 2; Xin-Nian Wang 3 1 Frankfurt Institute for Advanced Studies 2 IOPP 3 LBNL We updated the HIJING Monte Carlo model with the latest parton distribution functions and new set of the parameters in the two-component-model that controls total p+p cross section and the central pseudorapity density. We study hadron spectra and multiplicity distributions using the HIJING 2.0 model and compare to recent experimental data from p + p collisions at the LHC energies. Using a strong gluon shadowing effect, we can also give the prediction about hadron production in p+Pb and Pb+Pb collisions at LHC energies. The recent published LHC experiment results are in good agree- ment with our predictions within the experimental errors and theoretical uncertainties, including the central rapidity multiplicity and its centrality dependency in Pb+Pb collisions. 104 / 369 Measurement of J/ψ photoproduction in ultra-peripheral Au+Au collisions at √sNN=200GeV using the PHENIX detector Akihisa Takahara1 1 University of Tokyo The idea to use the strong electromagnetic fields present in high-energy nucleus nucleus collisions to study photoproduction at hadron colliders has attracted growing interest in recent years. PHENIX measured J/\psi photo-production in ultra-peripheal (UPC) Au+Au collisions at \sqrt{sNN} =200 GeV. We define central UPC trigger as events with no activity in the Beam-Beam Counters, but activity in ZDC and EMCal. This trigger selects the collisions with the impact parameter larger than twice thenuclear radius with a small background contribution from strong interactions. It provides a unique opportunity to study photo-production of hadrons by a strong electromagnetic field. The purpose of the measurement of J/\psi photo-production cross section in ultra-peripheral colli- sions is to probe the gluon distribution at low-x. We will report J/\psi cross section and its pT dependence measured using the high luminosity 2007 data. 117 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Global and collective dynamics / 370 Search for local strong parity violation in STAR using multiple observables Dhevan Gangadharan1 1 Department of Physics-Ohio State University Parity-odd domains from QCD are predicted to cause charge separation of quarks across the reaction- plane created in non-central relativistic heavy ion collisions–The Chiral Magnetic Effect [1]. Here we present several measurements to search for charge separation across the reaction-plane at STAR. We use three different observables: a three point correlator, a multiplicity asymmetry correlator, as well as a reaction-plane dependent balance function. The correlations are studied differentially and are presented for several Au+Au collision energies: 200, 62.4, 39, 11.5, and 7.7 GeV. We will discuss the sensitivities of these latest measurements to possible parity odd signals and parity even backgrounds. 118 / 371 Vorticity and Chaos in Heavy Ion Collisions Alexander Sorin1 Oleg Teryaev 1 1 Joint Institute for Nuclear Research P-odd effects related to medium vorticity are discussed. In particular, we suggest studying asep- aration of baryonic charge due to the large baryonic chemical potential. This separation could be manifested in neutron asymmetries in heavy ion collisions in the FAIR and NICA energy range. We analyze the vorticity in various chaotic flows in detail. Chaotic flows are generalized in a nontriv- ial way relevant to heavy ion collisions. We pay special attention to their symmetry properties, both discrete and continuous. The bounds for vorticity production in heavy ion collisions areob- tained. 149 / 372 Topological interactions of non-Abelian vortices with quasi-particles in high density QCD Yuji Hirono1 Muneto Nitta 2; Takuya Kanazawa 3 1 The University of Tokyo 2 Keio University 3 Universität Regensburg Non-Abelian vortices are topologically stable objects in the color-flavor locked (CFL) phase of dense QCD. We derive a dual Lagrangian starting with the Ginzburg-Landau effective Lagrangian for the CFL phase, and obtain topological interactions of non-Abelian vortices with quasi-particles such as 118 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / U(1)B Nambu-Goldstone bosons (phonons) and massive gluons. We find that the phonons couple to the translational zero modes of the vortices while the gluons couple to their orientational zero modes in the internal space. 59 / 373 √ J/ψ polarization in p+p collisions at s = 200 GeV at STAR Barbara Trzeciak1 1 Warsaw University of Technology Barbara Trzeciak for the STAR Collaboration Currently there are many models with different assumptions regarding J/ψ production mechanism that seem to describe the production cross section from experimental data reasonably well. Infor- mation on J/ψ spin alignment, commonly named as J/ψ polarization, may allow to discriminate J/ψ production models. Moreover the prediction that J/ψ polarization is transverse momentum depen- dent needs to be tested. √ Analysis of J/ψ polarization at mid-rapidity in p+p collisions at s = 200 GeV registered in the STAR experiment will be presented. Data were triggered by the STAR Electromagnetic Calorimeter. J/ψ is analyzed through its dielectron decay channel. The J/ψ polarization is extracted from the decay angular distribution measured in the helicity frame. Correlations and fluctuations / 374 Relativistic theory of hydrodynamic fluctuations Joseph Kapusta1 Berndt Muller 2; Misha Stephanov 3 1 University of Minnesota 2 Duke University 3 University of Illinois at Chicago Hydrodynamic fluctuations have been applied to a wide variety of physical, chemical, and biological phenomena in the past decade. In the context of high energy heavy ion collisions, there will be intrinsic fluctuations due to the finite size and finite particle content even if the initial conditions are fixed. We develop the theory of relativistic fluctuations, and apply it to a 1+1 dimensional boost invariant model. In analogy to the cosmic microwave background radiation, fluctuations might provide information on the equation of state, including a possible critical point, and on the transport coefficients. 94 / 375 Study of Λ − Λ correlations and search for the H-dibaryon with the STAR detector at RHIC 119 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Neha Shah1 1 UCLA Considerable experimental efforts have been devoted to search for the existence of H-dibaryon, a six quark state, proposed by Jaffe[1]. It has also been proposed that the H particle would appear as a bump in the Λ−Λ invariant mass spectra if the H is a resonance state, or the H would lead to a depletion of the Lambda-\LambdacorrelationnearthethresholdiftheHisweaklybound.Inthisscenario, themassofHisexpectedtobeintherange(2230, 2380)MeV.Becauseofhighrateofstrangeparticleproductionperheavyioncollision, RelativisticHeavyIonCollider(RHIC)isauniqueplacetosearchfortheH− dibaryon.T he\Lambda-\LambdacorrelationmeasurementsatRHICaresensitivetotheirmutualinteractions, whichcanbeusedtoprobewhetherthereisastableHparticleorHresonance.T hissensitivityisuniqueatRHICbecauseoftheallowedrangeof \Lambda- \Lambdascatteringparametersinnucleus−nucleuscollisions.W ewillpresentthemeasurementof \Lambda- \LambdacorrelationsinAu + Aucollisionsat\sqrt{s}=39GeV and\sqrt{s}=200$GeV using the STAR experiment at RHIC. [1] R. L. Jaffe, Phys. Rev. Lett. 38, 195 (1977). 150 / 376 Continuous Time Monte Carlo for QCD in the Strong Coupling Limit Wolfgang Unger1 Philippe de Forcrand 2 1 ETH Zürich 2 ETH Zürich, CERN We present results for QCD in the strong coupling limit, obtained from a worm-type algorithm on a discrete spatial lattice but with continuous Euclidean time. This is obtained by sending both 2 2 the anisotropy parameter γ = a/at and Nτ to infinity at fixed temperature T = γ /Nτ . The gain is that no continuum extrapolation for Nτ → ∞ has to be carried out. We contrast these computations with those obtained on discrete lattices for large Nτ . We discuss the determination of the critical temperature for U(3) (purely mesonic) in the chiral limit, and the extension to SU(3) (baryons included) with a baryon chemical potential. We finally discuss the possibility of a continuous time worm algorithm at finite quarkmass. Pre-equilibrium and initial state - 17 / 377 Radiative energy loss reduction in a plasma due to damping Marcus Bluhm1 Joerg Aichelin 1; Pol Bernard Gossiaux 1 1 Laboratoire SUBATECH The strong quenching of jets and the suppression of hadron spectra at high transverse momenta are striking experimental observations made in high energy nuclear collisions. Both have been interpreted as signature for the formation of a deconfined plasma of QCD matter, in which partons suffer a medium-induced energy loss.In theoretical studies devoted to a parton’s radiative energy loss, 120 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / however, the damping of radiation within the plasma has so far widely been neglected. We investigate the radiative energy loss per unit distance of a relativistic colour charge traversing as probe an infinite absorptive plasma. The Landau-Pomeranchuk-Migdal effect is incorporated as well as modifications due to the polarization of and damping mechanisms in the medium. The latter are phenomenologically described by a complex index of refraction, while the colour charge dynamics is considered in the Abelian approximation. We find a substantial reduction of the medium- induced mechanical work in addition to the well known Ter- Mikaelian effect from the polarization of matter. Moreover, the formation time of radiated quanta is also drastically reduced, both for small frequencies, where damping has a minor additional impact besides the polarization effect, and for larger frequencies. These effects are more pronounced for larger medium damping and/or larger initial energy of the charge. Therefore, we expect that our study will have a significant impact on the understanding of jet quenching phenomena in ultra- relativistic heavy-ion collisions at RHIC and even more at LHC. Heavy flavor / 379 Heavy quark diffusion from lattice QCD spectral functions Heng-Tong Ding1 Anthony Francis 2; Wolfgang Soeldner 3 1 Brookhaven National Lab 2 University of Bielefeld 3 University of Regensburg We analyze the low energy part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region 1.5 < T /Tc < 3 as well as for T ≃ 0.75Tc. We present evidence for the existence of a transport peak above Tc and its absence below Tc. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation wealso determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium. 127 / 380 Examining real-time functions on the lattice using inverse prop- agator and self-energy Masakiyo Kitazawa1 Masayuki Asakawa 1 1 Osaka University 121 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The inverse of a Euclidean correlation function has an analytic relation to the inverse of a corresponding retarded propagator in real time. We argue that this analyticy is exploited in the analysis of real-time functions with Euclidean correlator obtained in lattice QCD Monte Carlo simulations complementary to the standard analysis of spectral functions. We analyze the inverse of quark correlator obtained on the quenched lattice, and demonstrate that the inverse correlator contains information to constrain the form of the quark propagator in real time in addition to the standard analysis. For elementary fields the inverse correlator is directly related to the imaginary part of the self-energy in real time, which physically represents the rates of scattering processes due to the optical theorem. Implications of the present analysis to these microscopic aspects of the dynamical properties are addressed. 95 / 381 Local Parity Violation or Local Charge Conservation/Flow? A Reaction-Plane-Dependent Balance Function Study Hui Wang1 1 Michigan state university STAR has recently reported charge-dependent√ azimuthal correlations that are sensitive to the charge separation effect in Au+Au collisions at sNN = 200 GeV [1]. Qualitatively, these results agree with some of the theoretical predictions for local parity violation in heavy-ion collisions. However, a study using reaction-plane-dependent balance functions shows an alternative origin of this signal. The balance function, which measures the correlation between oppositely charged pairs, is sensitive to the mechanisms of charge formation and the subsequent relative diffusion of the balancing charges. The reaction-plane dependent bal- ance function measurements can be related to STAR’s charge-dependent azimuthal√ correlations. We report reaction-plane-dependent balance functions for Au+Au collisions at sNN = 200 , 62.4, 39, 11.5, and 7.7 GeV using the STAR detector. The model of Schlicting and Pratt [2] incorporating local charge conservation and elliptic flow reproduces most of the three-particle azimuthal correlation results at 200 GeV. The experimental charge-dependent azimuthal charge correlations observed at 200 GeV can be explained in terms of local charge conservation and elliptic flow. [1] B. I. Abelev et al. [STAR Collaboration], Phys. Rev. Lett. 103, 251601 (2009) and B. I. Abelev, et al. [STAR Collaboration], Phys. Rev. C 81, 054908 (2010). [2] S. Schlichting and S. Pratt, Phys. Rev. C 83, 014913 (2011) Correlations and fluctuations / 382 Eccentricity and elliptic flow in proton-proton collisions from parton evolution Yoshitaka Hatta1 Christoffer Flensburg 2; Emil Avsar 3; Jean-Yves Ollitrault 4; Takahiro Ueda 5 1 University of Tsukuba 122 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 2 Lund 3 Penn State 4 Saclay 5 Karlsruhe It has been argued that high-multiplicity proton-proton collisions at the LHC may exhibit collective phenomena usually studied in the context of heavy-ion collisions, such as elliptic flow. We study this issue using DIPSY, a brand-new Monte Carlo event generator which features almost-NLL BFKL dynamics and describes the transverse shape of the proton including all fluctuations. We predict the eccentricity of the collision as a function of the multiplicity and estimate the magnitude of the elliptic flow. We then compare the result with correlation from “nonflow” effects and suggest how to suppress the latter by applying cuts in the final state. 60 / 383 Light meson production in d+Au collisions measured by PHENIX experiment at sqrt(s_NN) = 200 GeV Dmitry Kotov1 1 PNPI RAS High pT particle suppression in heavy ion collisions appears to be one of the most exciting discov- eries at RHIC. The suppression is explained by jet-quenching via partonic energy loss inahotand dense matter created in such collisions. Nevertheless, theoretical models tuned to describe hadron suppression versus pT and centrality suffer from ambiguities in description of collision dynamics, parton energy loss and cold nuclear matter effects. The latter can be studied by looking atd+Au collisions since it can be safely assumed that no hot and dense medium is being created. The PHENIX experiment at RHIC has performed light meson production measurements ind+Au collisions at sqrt(s_NN) = 200 GeV. This poster will deliver the latest results obtained from high statistics 2008 data sample for omega, phi, k-short and eta-prime mesons. We will present analyses approaches used to obtain particle yields in different hadronic and leptonic decay channels andits nuclear modification factors. The poster will also concentrate on systematic study of neutral meson production in d+Au collisions at sqrt(s_NN) = 200 GeV. 130 / 384 Feasability study for a Muon Forward Tracker in ALICE Laure Marie Massacrier1 Antonio Uras 2 1 Institut de Physique Nucleaire de Lyon (IPNL)-Universite Claude 2 Institut de physique nucléaire de Lyon ALICE is the experiment dedicated to the study of the quark gluon plasma in heavy-ion collisions at the LHC. Improvement of ALICE sub-detectors for the upgrade plans of the year 2017 are ongo- ing. The Muon Forward Tracker (MFT) is a proposal in view of this upgrade. The MFT is aSilicon pixels detector added in the Muon spectrometer acceptance (-4 123 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / absorber. The MFT upgrade is motivated by several physics improvements. The measurement of the DCA (Distance of Closest Approach) of single muons and secondary vertex from dimuons will permit the identification of open charm (ctau~ 150 microns) and beauty (ctau ~ 500 microns) mesons. The MFT, thanks to its tracking capabilities, will allow to improve the mass resolution oftheres- onances for a better separation between rho/omega and phi, jpsi and psi prime,and upsilon family resonances. In addition, it will help to reject a large fraction of muons coming from pion and kaon decays, improving the signal over background ratio. Moreover, the MFT will lead to the direct mul- tiplicity measurement, event by event, of charged particles within the spectrometer acceptance. In order to evaluate the feasability of this upgrade, five Silicon planes were simulated within the Ali- Root framework. Effects of multiple scattering in the absorber and L3 magnetic field onmuonsin the MFT will be shown. A detailed study of the influence of the beam pipe geometry on secondary particles production was performed. Performances of the MFT in terms of occupancy rates in the pixel plans, secondary vertex measurement, improvement of the dimuon invariant mass resolution were established. The method used for tracking in the planes and matching between the muon tracks and MFT tracks will also be presented. Heavy flavor / 385 Quark recombination and heavy quark diffusion in hot nuclear matter Rainer Fries1 Min He 2; Ralf Rapp 2 1 Texas A&M University + RBRC 2 Texas A&M University We review resonance recombination for quarks and show that it is compatible with quark and hadron distributions in local thermal equilbrium. We then calculate realistic heavy quark phase space dis- tributions in heavy ion collisions using Langevin simulations with non-perturbative interactions in hydrodynamic backgrounds. We hadronize the heavy quarks on the critical hypersurface given by hydrodynamics after constructing a criterion for the relative recombination and fragmentation con- tributions. We discuss the influence of recombination and flow on the resulting heavy mesonand single electron R_AA and elliptic flow. We will also comment on the effect of diffusion ofopen heavy flavor mesons in the hadronic phase. 386 Dragging D mesons by hot hadrons Sabyasachi Ghosh1 Jan-e Alam 1; Santosh K Das 1; Sourav Sarkar 1 1 Variable Energy Cyclotron Centre We evaluate the drag and diffusion coefficients of a hot hadronic medium consisting ofpions, nucleons, kaons and eta using open charm mesons as a probe. The interaction of the probe with the hadronic matter has been treated in the framework of effective field theory. It is observed that the magnitude of both the transport coefficients are significant, indicating substantial amount of interaction of the heavy mesons with the thermal hadronic system. The results may have noticeable impact on the experimental observable like the suppression of single electron spectra originating form the decays of heavy mesons in nuclear collisions at relativistic energies. 124 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 131 / 387 Towards the realization of the CBM-Micro Vertex Detector: Tech- nological challenges and detector response simulation Christina Dritsa1 1 JLU The future Compressed Baryonic Matter (CBM) experiment, to be operated at the FAIR facilityat GSI, Darmstadt, aims at the exploration of the properties of dense baryonic matter. In particular, the search for in-medium modifications of hadrons, the study of the transition from hadronic to partonic degrees of freedom and the experimental search for a critical endpoint in the phase diagram of strongly interacting matter are among the principal physics goals of CBM. A major challenge of CBM is to measure rare and penetrating probes such as open charm, which is produced close to kinematical threshold at FAIR energies. Open charm identification is based on distinguishing the displaced decay vertices from the nuclear collision vertex. This approach calls for a performant vertex detector. The Micro Vertex Detector (MVD) proposed for CBM will consist of several layers of pixeldetec- tors. Currently, the most promising candidates are Monolithic Active Pixel Sensors (MAPS) which provide high granularity, low material budget, good radiation hardness and relatively good readout time. We will present the technological challenges of the MVD and approaches towards the realization of the detector. A new detector response model for simulating the MAPS sensors will be presented and related results will be shown. QCD Phase diagram / 389 Scale for the phase diagram of quantum chromodynamics Sourendu Gupta1 Bedanga Mohanty 2; Hans George Ritter 3; Nu Xu 3; Xiaofeng Luo 4 1 TIFR, Mumbai 2 VECC, Kolkata 3 LBNL, Berkeley 4 University of Science and Technology of China, Hefei We present a test of QCD in the non-perturbative domain through a comparison of thermodynamic fluctuations predicted in lattice computations with the experimental data of baryon distributions in high-energy heavy-ion collisions. This study provides evidence for thermalization in these collisions, and allow us to set a scale for the QCD phase diagram. The scale is the temperature for the cross over from normal nuclear matter to the deconfined quark gluon plasma phase. Extension ofthese techniques might allow the identification of the critical point of QCD. 119 / 390 Understanding the equilibration of matter from time-dependent correlator 125 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Shu Lin1 Erdmenger Johanna 1; Ngo Thanh Hai 1; Shuryak Edward 2 1 MPI for Physics, Munich 2 Stony Brook University The fast thermalization of Quark Gluon Plasma, as suggested by hydrodynamical simulation, isone of the central questions of heavy ion collisions. Theoretical understanding of the mechanism in- volves field theory out of equilibrium. While the perturbative method becomes less effective dueto the strong coupling, the gauge/gravity duality can play an important role. In [1], we studied a gravi- tational collapse model, which is dual to an equilibration process of a homogeneous QGP. We found that the near-equilibrium correlators of different operators approach their thermal counterpart in a universal fashion. As a first step to explore the far from equilibrium regime, we studied amodel with a moving mirror in AdS space [2]. We solved the spatially integrated time-dependent corre- lator in the dual field theory and found that the singularities of the correlator are consistent with the bulk-cone singularities conjecture [3]. Furthermore, we found a recursive relation among the leading order divergence of the singularities, which allow us to determine the divergences without solving the correlator explicitly [4]. Possible extension to a more realistic equilibration model will be discussed. [1] S.~Lin and E.~Shuryak, Phys.\ Rev.\ D {\bf 79} (2009) 124015 [arXiv:0902.1508 [hep-th]]. [2] J.~Erdmenger, S.~Lin and T.~H.~Ngo, JHEP {\bf 1104} (2011) 035 arXiv:1101.5505 [hep-th]. [3] V.~E.~Hubeny, H.~Liu and M.~Rangamani, JHEP {\bf 0701} (2007) 009 [arXiv:hep-th/0610041]. [4] J.~Erdmenger, C.~ Hoyos, S.~Lin and T.~H.~Ngo, to appear. 23 / 392 0 Methods for extracting elliptic flow (v2) and cocktail fits of ρ vector-meson in STAR at RHIC Prabhat Pujahari1 1 IIT Bombay In non-central nucleus-necleus collisions, the azimuthal angle of the outgoing particles are cor- related with the direction of the impact parameter and this phenomenon is known as anisotropic flow which is sensitive to the system properties evolved early in the collisions and hence provides evidence for the formation of a hot and dense medium created in such collisions. The measurement 0 of elliptic flow (v2) of short-lived particles (for instance ρ mesons) at Relativistic Heavy Ion Colli- sions is studied through their decay products. The main focus in our study is the hadronic decay channel of ρ0 where ρ0 → π+ + − 0 pt . The motivation of the ρ v2 measurement is to test quark number scaling as predicted by coales- cence models and to answer whether the ρ0 is directly produced or formed from pions in a hadronic 0 phase.√ In this poster, we present the results of v2 for ρ vector mesons in Au + Au collisions at 0 (sNN ) = 200 GeV from STAR. We discuss the extraction of the ρ yield with a hadronic cocktail fit after combinatorial background subtraction. We also discuss the invariant mass fit methodused 0 to measure the v2 for the ρ mesons in the presence of large background. 126 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 61 / 395 Charged Particle Ratios for p+p Collisions in √s = 62.4 GeV at RHIC Shikshit Gupta1 1 Department of Physics The ratios of particle production in hadronic interactions are important indicators of the collision dynamics [1]. These can be used to probe the process of hadronization in high energy collisions. We present measurements of mid-rapidity anti-particle to particle ratios in p + p collisions at √s = 62.4 GeV from the STAR experiment. The measurements of the anti-particle to particle ratios are studied as a function of transverse momentum (pT ) and comparison is made with corresponding ISR results for the p + p collisions at √s = 63 GeV [2]. Identification of charged hadrons (π^± , k^±, p and pbar) was done primarily through time projection chamber measurements. Charged hadrons are identified by using specific ionization energy loss (dE/dx) at the low momentum region [3]. References [1] H. Satz , Rep .Prog .Phys . 63 (2000) 151. [2] B. Alper et al., NuclearPhysicsB 100 (1975) 237-290. [3] B. I. Abelev et al., [STAR Collaboration], Phys .Rev .C 79 (2009) 34909. Hadron thermodynamics and chemistry / 396 The thermal model on the verge of the ultimate test: theLHC data Anton Andronic1 Johanna Stachel 2; Krzysztof Redlich 3; Peter Braun-Munzinger 4 1 Gesellschaft fuer Schwerionenforschung mbH (GSI) 2 University of Heidelberg 3 Wroclaw University 4 GSI In our model, both the light (u,d,s) quark sector and charm(onium) have found a unified description, thus providing very different probes for a possible delineation of the phase boundary between deconfined and hadronic matter produced in nucleus-nucleus collisions from low (AGS) energies up to RHIC energy. A purely thermal production (at chemical freeze-out) appears natural for u,d,s-carrying hadrons and a good degree of consensus has been achieved with the RHIC data, at least for central collisions. We are rather confident in predicting the chemistry of ligh-quark hadrons at the LHC. In contrast, charmed hadrons and charmonia can be produced at chemical freeze-out only as a result of a “distribution” into hadrons of charm quarks produced in primary hard collisions. Our model describes rather well the RHIC and SPS data on charmonia, which will be reviewed briefly. We expect that generation at the phase boundary is at the LHC the exclusive mechanism (thus lifting the present controversy whether charmonia melt or not in the deconfined stage at RHIC and SPS 127 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / energies). With some of the model ingredients (like the volume at chemical freeze-out) already constrained by the first LHC data, the main uncertainty in our predictions remains the charm cross section in Pb-Pb, where shadowing is not yet known. In addition to the overall hadron abundancies, including those of light (hyper)nuclei and their antiparticles, we provide predictions for charmonia and for charmed hadrons, to be confronted soon with the LHC data. 88 / 397 √ D meson reference spectra in pp collisions at s = 2.76~TeV with ALICE Zaida Conesa Del Valle1 1 CERN The ALICE experiment has the ability to measure D meson production in different colliding systems. Charm production in proton proton collisions is an important tool to test pQCD calculations in a new energy domain. Its spectrum in heavy ion interactions is influenced by the formation of hot and dense QCD matter. A common procedure to study the characteristics and effects of this matter is to compare particle production in heavy ion and proton proton reactions. √ Here we present√ a pQCD-based energy extrapolation of ALICE D meson pp measurements at s = 7~TeV to s = 2.76~TeV, as a reference√ for the PbPb studies at this energy. The status of the D0 → K− π+ analysis in pp collisions at s = 2.76~TeV will also be described. 151 / 398 Search for the QCD critical point by higher moments of the net- charge multiplicity distribution NIHAR R SAHOO1 1 Variable Energy Cyclotron Centre The Relativistic Heavy-Ion Collider (RHIC), at BNL, has undertaken its beam energy scan program in order to probe the QCD critical point. Theoretical calculations reveal that the higher moments of the multiplicity distribution of the conserved quantities like net- charge, net-baryon, net-strangeness are related to the corresponding susceptibilities and the correlation length of the system. These quantities show deviation from monotonic behavior at the CP compared to the other region. Here we report the first measurement of the moments (standard deviation,skewness and kurtosis) of the net-charge multiplicity distribution measured by the STAR detector for wider range of energies. The energy and centrality dependance of these higher moments and their products will bepresented for the 200 GeV, 39 GeV, 11.5 GeV and 7.7 GeV center of mass energies of the Au+Au collisions which correspond to the baryonic chemical potential from 20MeV to 550 MeV. Theoretical predictions, con- taining the non-CP physics, from the Hadron Resonance Gas models, HIJING and UrQMD models are compared with the data. 128 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Theory developments / 399 Interference effects in medium–induced gluon radiation Edmon Iancu1; Jorge Casalderrey Solana2 1 CEA Saclay 2 CERN The recent results at the LHC on jet quenching in heavy ion collisions call for a fundamental understanding of the evolution of a relatively hard jet propagating through a QCD medium like the quark–gluon plasma. As a first step in that sense, we consider the interference pattern for the medium–induced gluon radiation produced by a color singlet quark–antiquark antenna embedded in a QCD medium with size L. This setup is indeed well suited for studies of coherence phenomena like angular ordering. We focus on the most favorable kinematics for medium–induced gluon radiation√ in the BDMPS–Z regime, that is transverse momenta k⊥ ∼ qLˆ , short formation times τf ≪ L, and relatively large emission angles θ 1/3 gtrsimθf ≡ (ˆq/ω) (qˆ is the medium ‘jet quenching’ parameter and ω is the gluon energy). We demonstrate that, for a dipole opening angle θqq¯ larger than θf , there is no interference between medium–induced gluon emissions by the quark and the antiquark. That is, the in–medium contribution to the antenna pattern isthe incoherent superposition of two individual BDMPS–Z spectra. Physically, this is so since, unlike the direct emissions which can be delocalized anywhere throughout the medium, the interference terms are non–zero only for the very early emissions, such that the size of the qq¯ dipole at the time of emission be smaller than the transverse wavelength of the emitted gluon. 128 / 400 Ultrasoft Fermionic Mode in QED and QCD plasmas Yoshimasa Hidaka1 Daisuke Satow 1 RIKEN [email protected], [email protected] We discuss that the fermion spectrum at an ultrasoft energy region (≪g^2T) in quantum electrody- namics and quantum chromodynamics at high temperature T, where g is the coupling constant. We show that the fermion propagator has a pole at v|p|-i\gamma, where p is the momentum, v=1/3 is the velocity, and \gamma is the damping rate of order g^2T log(1/g). The residue of the pole is weak of order g^2. When a system has conserved charges, soft modes called hydrodynamic modes appear in the bosonic sector. These hydrodynamic modes are zero mode, i.e., the dispersion of thepoles is \omega=0 at p=0. The question is whether such a soft mode exists in the fermionic sector,when the system has a peculiar symmetry of the fermions. We show that the pole at the ultrasoft region is related to chiral symmetry, although it is not the exact zero mode. In order to obtain the correct pole, one have to sum over relevant diagrams beyond the hard thermal loop approximation even in the leading order of the coupling. This is similar to the calculation of transport coefficients [1].We 129 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / analytically obtain the pole of the fermion propagator and its residue in the leading order by solving a Bethe-Salpeter equation. Such pole was also suggested in Ref. [2], in which the self-consistent equation was shown; however it has not been solved. We also discuss whether this phenomena is robust in the fermion-boson system in the chiral limit. References [1] S. Jeon, Phys. Rev. D52, 3591 (1995); Y. Hidaka and T. Kunihiro, Phys. Rev. D 83, 076004 (2011). [2] V. V. Lebedev and A. V. Smilga, Annals Phys. 202, 229 (1990). 60 / 401 Measurement of J/Ψ elliptic flow in Au+Au collisions at √sNN=200 GeV in STAR experiment Hao Qiu1 1 Institute of Modern Physics J/Ψ elliptic flow (v2) is sensitive to both the J/Ψ production mechanism and the elliptic flowofheavy quarks. While some models predict that J/Ψ produced through direct nucleon-nucleon process have very limited v2, J/Ψ produced by the recombination of c and cbar pairs could carry finite v2, de- pending on the interaction between charm quarks and the medium. Furthermore, due to their long relaxation time, heavy quarks are expected to thermalize much more slowly than light flavor quarks. Thus the study of J/Ψ v2 will also shed light on the extent to which the collision system isthermal- ized at RHIC. In year 2010, with the combined particle identification capability from STAR’s Time Projection Cham- ber, Barrel Electromagnetic Calorimeter and the newly installed Time of Flight detector, STAR is able to clearly identify electrons from J/Ψ decay over a wide momentum range. To cope with the large data volume coming from collisions at high luminosity, a High Level online tracking Trigger was implemented to reconstruct J/Ψ events online and tag them for fast analysis. In addition, the low material budget in STAR setup in run 2010 allows us to dramatically improve J/Ψ identification, with unprecedented statistics. In this talk, we present J/Ψ v2(pT) measurement from 200 GeV AuAu colli- sions measured by the STAR experiment. This analysis is based on 350 million minimum bias events plus high tower triggered events equivalent to about 7 billion minimum bias events in the relatively higher transverse momentum region. The results of the collision centrality dependence of theJ/Ψ v2(pT) will be presented. Comparisons to models will be made and the implications on collision dynamics at RHIC will be discussed. Hadron thermodynamics and chemistry / 402 Measurement of light vector mesons by PHENIX experiment at RHIC Deepali Sharma1 1 Weizmann Institute of Science The PHENIX experiment at RHIC has carried√ out systematic measurements of ϕ and ω mesons in p + p, d + Au, Cu + Cu and Au + Au collisions at sNN = 200 GeV. Consistent results have been obtained using leptonic and hadronic decay modes as well as different analysis techniques. In p + p collisions, the transverse momentum distributions of ω and ϕ, as well as all other mesons measured by PHENIX, are well described by the Tsallis distribution functional form. Combining the e+e− and hadronic (ω → π0gamma, π0π+π−, ϕ → K+K−) decay channels, ω and ϕ have been 130 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / measured over a pT range of 0 - 13.5 GeV/c and 0 - 7 GeV/c respectively. New results obtained using hadronic and dielectron channels of ω and ϕ mesons in d + Au collisions extend the pT coverage to 0.25 - 13 GeV/c and 0 - 7 GeV/c respectively, and reveal a moderate enhancement at intermediate pT and a hint of suppression at pT > 8 GeV/c. Both observations are consistent with previous results 0 + − + − for π , π + π , Ks and K + K . The nuclear modification factor of ω in Cu + Cu and Au + Au collisions measured over a pT range of 4 - 12 GeV/c, shows that ω has a similar suppression pattern as that of π0 and η, strengthening the observation that mesons with different masses have similar behavior but different from theoneof baryons. However, ϕ in Cu + Cu and Au + Au collisions, measured from 1 - 7 GeV/c, shows a sup- 0 pression, that is smaller than that of the π and η in the intermediate pT range (2 - 5 GeV/c), whereas at higher pT , within the large experimental uncertainties,√ the amount of suppression appears similar to that of the light mesons. Results of ϕ production at sNN = 62.4 GeV show a similar behavior but with larger uncertainties. This talk will review the most recent results obtained for light vector mesons in different collision systems and energies. 132 / 403 Charmonium production on fixed target with proton and lead beams of LHC Alexeii Kurepin1 Marina Golubeva 1; Natalia Topilskaya 1 1 Institute for Nuclear Research (INR) Charmonium production on fixed target with proton and lead beams of LHC. A.B.Kurepin, N.S.Topilskaya, M.B.Golubeva Institute for Nuclear Research of the Russian Academy of Sciences, 117312 Moscow, Russia Fixed target operation with proton and lead beams of LHC provides new possibilities for investigation of a mechanism of quarkonium production and suppression with good statistics at the energy interval between SPS and RHIC The dissociation of heavy quark resonances by colour screening in a deconfined medium isoneof the possible signature of Quark Gluon Plasma formation in high energy heavy ion collisions. Inves- tigation of charmonium production by decay on two leptons (muons) was started at the CERN SPS [1], continued at RHIC [2,3] and now is going at LHC, CERN. The theoretical models without regeneration that could reproduce SPS results produce too strong J/ψ suppression at RHIC energies. At LHC energy a process of charmonium production is different with respect to the SPS and even to the RHIC. The theoretical estimates give different results, some predict strong suppression [4], some predict enhancement [5]. In addition to prompt production from hard scattering, charmonium states could be produced due to recombination which maygive an enhancement instead of a suppression. The energy interval between SPS and RHIC is very important for a study of the mechanism ofquarko- nium production and suppression. If the proton and ion beams will be used at LHC with fixed targets, the energy for 7 TeV proton beam will be s = 114.6 GeV, for 2.75 TeV Pb beam s = 71.8 GeV. In order to separate normal and anomalous charmonium suppression we need to have data for pp interaction and several target nuclei, which is easy to do with fixed target and very hard with collid- ing beams. As it was already used for the experiment on collider with a fixed target at HERA-B, the target in the form of thin ribbon could be placed around the main orbit of LHC. The life time of the beam is determined by the beam-beam and beam-gas interactions. Therefore after some time the particles will leave the main orbit and interact with the target ribbon. So for fixed target measurements only halo of the beam will be used and no deterioration of the main beam will be introduced. The experi- ments at different interaction points will not feel any presence of the fixed target. In order to study a capability of using the fixed target at LHC for charmonium production we calcu- late geometrical acceptances for J/ψ production, compare acceptances at collider experiments (RHIC 131 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / and LHC) with existing fixed target experiments. Then we estimate the counting rates andshow that J/ψ production on fixed target at LHC could be measured with rather high statistics collected in several days of data taking. [1] L. Kluberg, Eur. Phys. J. C 43, 145 (2005). [2] PHENIX Collab. (A. Adare et al.), Phys. Rev. Lett. 98, 232301 (2007). [3] M. J. Leitch, J. Phys. G 34, S453 (2007). [4] R. L. Thews et al., Eur. Phys. J. C 43, 97 (2005). [5] A.Andronic, P.Braun-Munzinger, K.Redlich, J.Stachel, Phys. Lett. B571, 36-44 (2003). 134 / 405 Completion of mass production of silicon pixel ladders for PHENIX silicon vertex tracker (VTX) MAKI KUROSAWA1 1 RIKEN The PHENIX detector had been upgraded with the silicon vertex tracker (VTX) to extend itsphysics capability in both the heavy ion and spin programs at Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The main role of VTX is precision measurement of heavy flavor. The VTX comprises a four-layer barrel detector built from two inner silicon pixel detector andtwo outer silicon strip detector. A silicon pixel ladder is the basic component of a silicon pixel detector. The two inner layers of the silicon pixel detectors are made up of 30 silicon pixel ladders. Eachsilicon pixel detector consists of four pixel hybrid sensors, two readout buses and a support board for cooling of sensor modules. Each components are glued with epoxy resin, and the pixel hybrid sensors and readout buses are connected electrically with bonding wires. In order to avoid increase of material budget, it is needed to reduce the thickness of resin. Furthermore, it is required to assemble with a precision less than 25 um. In satisfying these requirements, the mass production of silicon pixel detectors had been successfully completed. This poster provides details of mass production of silicon pixel ladders. 18 / 407 √ Underlying event studies in d+Au collisions at sN N=200 GeV from STAR Jana Bielcikova1 1 Nuclear Physics Institute ASCR Description of heavy-ion collisions, where modifications of the fragmentation functions due toin- teraction of partons with the hot and dense medium are expected, is a challenging task and requires a detailed understanding of small collision systems such as p+p and d+Au. Comparison of measure- ments in p+p and d+Au collisions can be further used to disentangle initial state effects from cold nuclear matter effects. Particles produced in p+p and d+Au collisions originate not only from hard scatterings, but soft and semi-hard multiple parton interactions and initial- and final-state radiation combine to produce particles at mid-rapidity which constitute the so called underlying event. The STAR collaboration√ at RHIC recently presented first results on underlying event properties in p+p collisions at sN N=200 132 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / GeV. We√ extend these studies and investigate in detail properties of underlying event in d+Au colli- sions at sNN =200 GeV. The analysis is based on the large d+Au data sample collected by theSTAR experiment in year 2008. The extracted underlying event properties are compared to those from p+p collisions. The obtained results will serve as input to Monte Carlo models. 96 / 408 Fluctuations and the Ridge from RHIC to LHC George Moschelli1 Sean Gavin 2 1 Frankfurt Institute for Advanced Studies 2 Wayne State University LHC and RHIC experiments exhibit a ridge-like enhancement of two particle correlations that is narrow in relative azimuthal angle ∆ϕ and broad in relative pseudorapidity ∆η. Causality implies that correlations between particles sepa- rated by a large ∆η must originate at the moment of production. These measurements can therefore reveal how particle production occurs. We were among the first to point out that such correlations can emerge as a consequence of fluctuating initial conditions and the subsequent transverse expan- sion. Taking the initial fluctuations as resulting from Glasma flux tubes, we successfully describe available ridge measurements, including the collision energy, centrality, and transverse momentum, dependencies of the ridge amplitude and azimuthal width. The effect of initial fluctuations onjet production and quenching has also been studied. In this talk we explore the impact of spatial triangularity of the Glasma flux tubes on the ∆ϕ depen- dence of two particle correlations. Our approach exploits the relationship between fluctuations and correlations and is compatible with multiplicity and pt fluctuation measurements. We calculate v3 in our approach and compare to other model predictions. Additionally, we present our prediction for the ridge in Pb+Pb collisions at the LHC, and compare our model to the ridge recently seen by CMS in high multiplicity 7 TeV proton-proton collisions, a measurement that could illuminate the interplay between hard and soft particle production. 62 / 409 Measurement of Baryonic Resonances in pp Collisions at the LHC with ALICE Ayben Karasu Uysal1; Benjamin Dönigus2 1 Department of Physics, Yildiz Technical University, Istanbul, Turkey 2 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm- stadt, Germany & Helmholtz Research School H-QM, Frankfurt, Germany The measurement of short-lived resonances allows the investigation of the collision dynamics and of the properties of the hot and dense medium created in high-energy collisions. We study the production of the two hadronic resonances Δ++(1232) → pπ+ and Λ(1520) → pK− in pp collisions at √s = 7 TeV with the ALICE apparatus at the LHC as a baseline for heavy-ion collisions. We present the performance of the reconstruction and transverse momentum spectra. The Δ++(1232)/p and Λ(1520)/Λ0 133 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / ratios obtained from previous pp collisions and thermal model calculations are also presented. Electromagnetic probes / 410 Direct photon production in heavy ion collisions in PHENIX ex- periment at RHIC Edouard Kistenev1 1 Brookhaven National Laboratory E.Kistenev for the PHENIX Collaboration Direct photon production in heavy ion collisions in PHENIX experiment at RHIC Among the observables used to probe the high temperature and high density phase of heavy nucleus collisions direct photons are considered of particular interest. At LO direct photons are produced in quark-gluon Compton scattering and quark-antiquark annihilation, the NLO processes are dom- inating in bremsstrahlung and fragmentation photon production and jet re-interaction in medium, QGP and hot hadronic stage emit thermal photons. Correlated measurements of the transverse mo- mentum dependence of direct photon production in collisions of different species and of underlying event observables, like isolation or flow, as well as the nuclear modification factor may give insight into the relative contribution from various production mechanisms. Extracting the direct photon signal from the large hadron decay background is experimentally chal- lenging particularly at lower transverse momenta and high multiplicities. PHENIX used a combi- nation of techniques based upon virtual (via low to intermediate mass e+e- pairs) and real (neutral clusters in calorimeters and reconstructed e+e- pairs from photon conversions) photon measure- ments to determine direct photon yields in the range of transverse momenta up to about 20 GeV/c for a wide range of energies and colliding species. In this talk we present recent PHENIX results on total direct photon production in pp, dA and AA collisions with emphasis on azimuthal correlations and nuclear modification. Implications of the PHENIX measurements for the initial temperature and density estimates as well as for the space- time evolution of the fireball will also be discussed. 61 / 411 J/\psi production at mid-rapidity in pp collisions at \sqrt{s}=7 TeV, measured with ALICE Ionut Cristian Arsene1 1 Gesellschaft fuer Schwerionen forschung mbH (GSI) The J/\psi production mechanism in proton-proton collisions is not fully understood and the mea- surement of the cross-section at LHC energies will bring new constraints on theoretical models. The production of charm quarks takes place in the early collision stages. Therefore, in thecaseof heavy ions, they probe the hot and dense quark-gluon medium that is expected to be formed in the collision. The understanding of the J/\psi production in pp collisions is important also as areference for the same measurement in heavy ion collisions. 134 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / We will report on the J/\psi production cross-section at mid-rapidity (|y|<0.9) in proton-proton col- lisions at \sqrt{s} = 7 TeV measured with the ALICE detector. We will show integrated and p_{t} dependent cross-sections, down to p_{T}=0, measured using the di-electron decay channel. Compar- isons with theoretical calculations and measurements in other experiments at lower energies and the LHC will be presented, as well as the status and prospects for the same measurement in Pb-Pb collisions at \sqrt{s_{NN}}=2.76 TeV. Energy scan / 412 QCD critical point and event-by-event fluctuations Misha Stephanov1 Christiana Athanasiou 2; Krishna Rajagopal 2 1 UIC 2 MIT Observables measuring the magnitude and non-Gaussianity of event-by-event fluctuations can be used to discover the QCD critical point in heavy-ion collisions. I shall describe theoretical predictions for the non-Gaussian measures such as skewness, kurtosis and corresponding mixed moments as a function of the beam energy in the presence of the QCD critical point. I shall discuss implications for the RHIC Beam Energy Scan and what we can learn from recent data. 24 / 413 Measurement of dNch/deta with the ALICE VZERO detector in central Pb-Pb collisions at 2.76 TeV Maxime Rene Joseph Guilbaud1 1 Institut de Physique Nucleaire de Lyon (IPNL)-Universite Claude ALICE (A Large Ion Collider Experiment) is the LHC experiment dedicated to the study of heavy- ion collisions. The aim of ALICE is to study the properties of a state of deconfined nuclear matter, the Quark Gluon Plasma (QGP), which lattice QCD predicts to be created at the extreme temper- atures and energy densities accessible in such collisions.The VZERO detector, made of scintillator hodoscopes on both sides of the interaction point, is covering the rapidity ranges 2.8 < eta < 5.1 and −3.7 < eta < −1.7. These pseudo-rapidity ranges rely on the nominal interaction point position. Thanks to the de-bunching effect of the LHC Pb beams, the VZERO is able to measure thecharged particles multiplicity in a large range of pseudo-rapidity (0.7 < |eta| < 5.2). In this poster, the detector and the analysis methods are described. The corresponding results of dNch/deta measure- ments are presented. 62 / 414 Reconstruction and first observation of the charmed baryon Λc in pp collisions at √s = 7 TeV with ALICE Rosa Romita1 135 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Gesellschaft fuer Schwerionen forschung mbH (GSI) ALICE is the dedicated LHC experiment to identify and characterize the quark gluon plasma in high- energy nuclear collisions. Due to their large mass and their generation at the early collision stage, heavy quarks are ideal probes. It is still an open question whether the baryon over meson enhance- ment at intermediate momentum as observed at RHIC also holds for the heavy-quark sector. We report on the analysis strategy to reconstruct the charmed baryon Λc in its hadronic decay chan- nel Λc -> p K- π+ and first results on the p-p data sample at 7 TeV recorded by the ALICE detector in 2010. Both topological selections and particle identification are exploited. The Λc signal in several pT intervals will be shown. 25 / 415 Equilibration in classical Yang-Mills dynamics Akira Ohnishi1 Andreas Schafer 2; Arata Yamamoto 3; Berndt Muller 4; Teiji Kunihiro 1; Toru T. Takahashi 5 1 Kyoto University 2 Regensburg University 3 University of Tokyo 4 Duke University 5 Gunma National College of Technology Understanding the mechanisms causing rapid thermalization deduced for high-energy heavy ion collisions is still a challenge. Thermalization is not fast enough in perturbative esitmate, and several instabilities in the classical Yang-Mills (CYM) equation have been considered. In this work, we have evaluated the equilibration time from the chaotic behavior of CYM [1]. We have developed a method to evaluete intermediate Lyapunov exponents (ILEs) by integrating the equation of motion for an intermediate time period. Sum of positive ILEs gives the entropy production rate in intermediate times, and is found to follow (energy density)^{1/4} as expected from the scale invariance of CYM. As a phenomenological application we conclude that for pure gauge theories with random initial conditions thermalization occures within few fm/c, an estimate which can be reduced by the inclusion of fermions, specific initial conditions etc. [1] T. Kunihiro, B. Muller, A. Ohnishi, A. Schafer, T.T. Takahashi, A. Yamamoto,Phys. Rev. D {\bf 82} (2010), 114015 [arXiv:1008.1156]. 152 / 417 Critical behavior of Binder-like ratios and ratios of higher cumu- lants of conserved charges in QCD deconfinement phase transi- tion Yuanfang Wu1 Lizhu Chen 1; Xiaosong Chen 2; Xue Pan 1 136 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Institute of Particle Physics, Huazhong Normal University 2 Institute of Theoretial Physics, Chinese Academy of Sciences Binder-like ratios of baryon number are firstly suggested in relativistic heavy ion collisions. Using 3D-Ising(O(1)), O(2), and O(4) models, the critical behavior of Binder-like ratios and ratios of higher cumulants of order parameter are fully presented. Binder-like ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. From low to high temperature through the critical point, the ratios of third cumu- lants change their values from negative to positive in a valley shape, and ratios of fourth cumulants oscillate around zero. The normalized ratios, like the Skewness and Kurtosis, do not diverge with correlation length, in contrary with corresponding cumulants. Applications of these characters in locating critical point in relativistic heavy ion collisions are fully discussed. 63 / 418 Identifying multi-quark hadrons from heavy ion collisions Sungtae Cho1 Akira Ohnishi 2; Che Ming Ko 3; Daisuke Jido 2; Koichi Yazaki 4; Marina Nielsen 5; Shigehiro Yasui 6; Su Houng Lee 1; Takayasu Sekihara 2; Takenori Furumoto 2; Tetsuo Hyodo 7 1 Yonsei University 2 Yukawa Institiute for Theoretical Physics 3 Texas A&M University 4 RIKEN 5 Universidada de Sao Paulo 6 IPNS, KEK 7 Tokyo Institute of Technology We propose a new approach of using relativistic heavy ion collisions to identify and study multi- quark hadrons. We focus on the expected production yields of these hadrons and show that their production yields are strongly affected by their internal structure [1], e.g. multi-quark configurations or hadronic molecules. We mainly use the coalescence model, which was successful in explaining the enhanced production of baryons at midrapidity in the intermediate transverse momentum region [2, 3] and the quark num- ber scaling of the elliptic flow of identified hadrons [4]. Based on the coalescence model, we areable to take into account the effects of the internal structure of hadrons, such as the angular momentum and the multiplicity of quarks [5. 6], on their production yields. We also rely on the statistical model [7], which has been known to describe the relative yields of normal hadrons very well, to extract important parameters for the coalescence model and normalize the expected yields. We find that the ratio of the production yields of normal hadrons calculated in the coalescence model to those from the statistical model, N^{coal}/N^{stat}, is in the range 0.2 137 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / [1] S. Cho et al. [ExHIC Collaboration] arXiv:1011.0852 [nucl-th] [2] V. Greco, C. M. Ko, and P. Levai, Phys. Rev. Lett. 90, 202302 (2003), Phys. Rev. C 68, 034904 (2003) [3] R.J. Fries, B. Muller, C. Nonaka, and S. A. Bass, Phys. Rev. Lett. 90, 202303 (2003), Phys. Rev.C 68, 044902 (2003) [4] D. Molnar and S. A. Voloshin, Phys. Rev. Lett. 91, 092301 (2003) [5] Y. Kanada-En’yo and B. Muller, Phys. Rev. C 74, 061901(R) (2006) [6] L. W. Chen, C. M. Ko, W. Liu, and M. Nielsen, Phys. Rev. C 76, 014906 (2007) [7] A. Andronic et al. Nucl. Phys. A 772 167 (2006) 120 / 419 Extended Schematic Model for Hadrons, and What Happens to the Radius of an Excited Hadron Tamar Friedmann1 1 University of Rochester It is well-known that making reliable predictions about low-energy QCD and hadrons is a great chal- lenge, as perturbative methods of quantum field theory do not apply when the coupling constant is strong. The common approach has been to propose various dynamical models which are inspired by assumptions, ideas, and intuition borrowed from physical systems which are not QCD. In this talk, I present refs. 1, 2 below. I will show how a schematic model employing pure QCD ingredients can teach us about the dynamics of QCD. I will present a new extended schematic model for hadrons where diquarks serve as building blocks on equal footing with quarks, and use it to reclassify the hadron spectrum. The outcome is that there are no radially excited mesons and no radially excited baryons; mesons and baryons which were believed to be radially excited are actually orbitally ex- cited states involving diquarks. The reclassification thereby provides a new set of relations between two fundamental properties of hadrons: their size and their energy. The relations state that the size of a hadron is largest in the ground state and shrinks when the hadron is excited, contrary to prac- tically all dynamical models proposed for QCD where the quarks are allowed to be pushed apart by a centrifugal barrier or radial excitations. While this set of relations appears counter-intuitive, it provides a novel explanation for the relationship between confinement and asymptotic freedom. It shows that we can overcome confinement and reach asymptotic freedom by increasing a hadron’s orbital excitation: the path from confinement to asymptotic freedom is a Regge trajectory. This sheds new light not only on the low energy regime of QCD but also on its connection with high energies. It is significant that the above set of relations predicts a QCD effect whereby a hadron can shrink.It is especially important since protons and neutrons, which make up the bulk of ordinary matter, are hadrons, and as such they obey the said relations. Our prediction proved to be concrete and testable when it was confirmed by an experiment that showed that the size of the proton shrinks (Pohlet. al., Nature 466, 213) nine months after this work was posted. 1. T. Friedmann, “No radial excitations in low-energy QCD I: Diquarks and classification of mesons,” arXiv: 0910.2229. 2. T. Friedmann, “No radial excitations in low-energy QCD II: Shrinking radius of hadrons,”arXiv:0910.2231. Theory developments / 420 Fluctuation, dissipation, and thermalization in non-equilibrium AdS5 black hole geometries 138 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Derek Teaney1 Paul Chesler 2; Simon Caron-Huot 3 1 Stony Brook University 2 MIT 3 Institute of Advanced Study We give a simple recipe for computing dissipation and fluctuations (commutator and anti-commutator correlation functions) for non-equilibrium black hole geometries. The recipe formulates Hawking radiation as an initial value problem, and is suitable for numerical work. We show how to package the fluctuation and dissipation near the event horizon into correlators on the stretched horizon. These horizon correlators determine the bulk and boundary field theory correlation functions. In addition, the horizon correlators are the components of a horizon effective action which provides a quantum generalization of the membrane paradigm. In equilibrium, the analysis reproduces previous results on the Brownian motion of a heavy quark. Out of equilibrium, Wigner transforms of commutator and anti-commutator correlation functions obey a fluctuation-dissipation relation at high frequency. 135 / 421 A Forward Calorimeter (FoCal) as upgrade for the ALICE Experi- ment at CERN Gerardus Nooren1; Martijn Reicher1; Sanjib Muhuri2; Taku Gunji3; Tomoya Tsuji3 1 Universiteit Utrecht 2 Variable Energy Cyclotron Centre; Department of Atomic Energy; Government of India; 1/AF, Salt-Lake, Bidhan- nagar; Kolkata–64. 3 Center for Nuclear Study University of Tokyo [email protected], [email protected], [email protected], [email protected] As an upgrade of the ALICE experiment at the CERN-LHC, we would like to build and install a For- ward Electromagnetic Calorimeter (FoCal) to be placed in the pseudorapidity region of 2.5 < η < 4.5, at the position of the existing Photon Multiplicity Detector (PMD). The basic motivation of including the calorimeter in the forward direction is to study outstanding fundamental QCD problems at low Bjorken-x values, such as parton distributions in the nuclei, test of pQCD predictions and to probe high temperature and high density matter in greater detail. A comprehensive measurement ofp-p, p-Pb and Pb-Pb collisions at the highest LHC energies will be required. For these measurements, the detector needs to be capable of measuring photons for energies up to at least E ~200 GeV/c. It should allow discrimination of direct photons from neutral pions in a large momentum range and should also provide reasonable jet energy measurements. At present, two possible designs are being considered based on silicon-tungsten calorimetry. We will present physics motivation of this project, measurement items, conceptual detector candidates, and basic performance for the measurements in this poster presentation. 77 / 422 Nonperturbative Particle Production in Boost-Invariantly Expand- ing Electric Fields and Two-Particle Correlations 139 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Naoto Tanji1 1 High Energy Accelerator Research Organization, KEK Nonperturbative particle production via the Schwinger mechanism has been studied as a mechanism of matter formation in the context of heavy-ion collisions. In the color flux model, the generationof longitudinal color-electric fields between two Lorentz-contracted nuclei receding from each other has been assumed. These electric fields polarize the vacuum and produce quarks and gluons. Also in the framework of the color glass condensate, the formation of longitudinal electric fields and longitudinal magnetic fields as well has been predicted. One of characteristics of these electric fields is its boost-invariance in the longitudinal beam direction. In an ideal situation where two nuclei run at exactly the speed of light, the electric fields span only inside the forward light cone and their configuration is symmetric under the longitudinal boost transformation. We study the dynamics of nonperturbative particle pair creation in such boost-invariantly expanding electric fields. The proper-time evolution of momentum distributions of created particles, which preserve the boost invariance of the background field, will be presented. The particles have the same velocity distributions as the flow velocity of the Bjorken flow from the first instance theyare created. We will also present the results on the calculation of the two-particle correlation between particles produced in the boost-invariant field. The correlation is short-range with respect to the transverse momentum, which originates in the Bose-Einstein correlation, and is long-range with respect to the longitudinal rapidity. This long-range rapidity correlation arises because the particles arecre- ated not as an eigenstate of a longitudinal momentum, which violates the boost-symmetry, but as a superposition of several momentum modes preserving the boost-symmetry. 26 / 423 Contribution from hard partons to the bulk elliptic flow Boris Tomasik1 Peter Levai 2 1 Czech Technical University in Prague - Prague - Czech Republic 2 MTA KFKI RMKI Large number of semi-hard partons deposit their energy and momentum in nuclear collisions at the LHC. Hereby they can induce collectively moving streams within the hydrodynamically behaving bulk matter. Although the production of hard partons is isotropic, in non-central collisions wehave an anisotropy of their spatial distribution. We argue that via the interaction of the produced streams the spatial anisotropy is translated into an anisotropy of the collective expansion of the bulk matter. This is demonstrated with the help of a simple toy model. The effect is estimated to bepotentially responsible for about 25% of the observed elliptic flow at the LHC. 136 / 424 The ALICE Inner Tracking System: performance with proton and lead beams Massimo Masera1 140 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Universita degli Studi di Torino [email protected], [email protected] The Inner Tracking System (ITS) of the ALICE experiment consists of six cylindrical layers ofsilicon detectors, exploiting three different technologies: pixel detectors for the innermost 2 layers, driftde- tectors for the two central layers and double sided strip detectors for the last two layers. Each layer has hermetic structure in r-phi and it is coaxial with the beam pipe. The ITS covers the pseudorapid- ity range |eta|<0.9 and its distance from the nominal beam line ranges from 3.9 cm for the innermost layer up to 43 cm for the outermost. The overall number of independent sensors is 2198 andthe spatial alignment of the ITS requires the determination of about 13000 parameters. The ITS main functions are those of providing both primary and secondary vertices reconstruction, of improving the ALICE barrel tracking capabilities in the vicinity of the interaction point and of improving the momentum resolution at high pT. Furthermore, as a standalone tracker, the ITS recovers particles which are missed by the external barrel detector, due to acceptance limitations. After a short summary on the status of spatial alignment and detector calibration, this talkwill cover the ITS performance with p-p and Pb-Pb collisions in 2010 for what concerns vertexing and tracking. 63 / 425 Hunting electrons from heavy-flavour hadron decays with the ALICE Transition Radiation Detector in proton-proton collisions at √s = 7 TeV Markus Fasel1 1 Gesellschaft fuer Schwerionen forschung mbH (GSI) The measurement of the production of heavy-flavour hadrons in proton-proton collisions isacru- cial test for perturbative QCD. Additionally it provides the reference for heavy-flavour studies in heavy-ion collisions. Thanks to its excellent electron identification capabilities the ALICE detector is well suited for the measurement of the open heavy-flavour cross section via single electrons. A first measurement of the cross section was performed with electrons identified by the ALICETime Projection Chamber and the Time-of-Flight detector. The Transition Radiation Detector provides a major contribution to the identification of electrons and allows to extend the inclusive electron spectrum up to transverse momenta around 10 GeV/c. During the data taking in 2010, 7 out of 18 supermodules were installed, covering 340° < φ < 40° and 140° < φ < 220° and |η| < 0.9. We show the performance of the electron identification with the Transition Radiation Detector in the analysis of electrons from heavy-flavour hadron decays. 426 Nuclear suppression at non-zero baryonic chemical potential Santosh K Das1 Bikash Sinha 1; Jan-e Alam 1; Payal Mohanty 1 1 Variable Energy Cyclotron Centre The drag and diffusion coefficients of heavy quarks propagating througha baryon rich quark gluon plasma have been calculated. The nuclear suppression factor, RAA for non-photonic single electron spectra resulting 141 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / from the semileptonic decays of heavy flavour mesons have been evaluated. The role of non-zero baryonic chemical potential on RAA has been highlighted. Correlations and fluctuations / 427 New results on event-by-event ratio fluctuations in PbPb colli- sions at CERN SPS energies Tim Schuster1 1 Frankfurt Institute for Advanced Studies, Goethe-University Frankfurt Event-by-event fluctuations of hadron ratios characterize the hadro-chemical composition ofthe hot and dense medium created in heavy-ion collisions. This makes the fluctuation signal sensitive to changes in the underlying structure of matter, and phase transition effects in particular. IntheSPS energy range, inclusive hadronic observables indicate the onset of the deconfinement phase tran- sition [1], making ratio fluctuations a promising observable to further characterize the transition and possibly reveal signatures of the conjectured critical point as suggested by lattice calculations of quark number susceptibilities at finite mu_B [2]. Kaons and protons carry large parts ofthecon- served quantities strangeness and baryon number. Their correlation, reflected in the kaon-to-proton ratio fluctuations, is expected to undergo a significant change at the anticipated parton-hadron phase boundary [3]. Results on (K+ + K−)/(p + pbar) and K+/p fluctuations in heavy-ion collisions will be presented for the first time. At 5 energies between sqrt(s_NN) = 6.3 and 17.3 GeV, sigma_dyn has been evaluated in central Pb+Pb collisions. For both ratios, a fast transition from positive sigma_dyn at low SPS energies to negative values at the higher energies is observed, an energy dependence that is not reproduced by hadronic models. While hadronic transport models predict almost constant fluctua- tions in the SPS energy range, a multiplicity scaling as suggested in [4] is also incompatible with the data. This study is complemented by new results on the centrality dependence of ratio fluctua- tions at sqrt(s_NN) = 17.3 GeV, which confirm the systematics recently reported at RHIC energies [5]. References [1] C. Alt et al. [NA49 Collaboration], Phys. Rev. C 77, 024903 (2008) [arXiv:0710.0118 [nucl-ex]]. [2] M. Cheng et al., Phys. Rev. D 79, 074505 (2009) [arXiv:0811.1006 [hep-lat]]. [3] V. Koch, A. Majumder and J. Randrup, Phys. Rev. Lett. 95, 182301 (2005) [arXiv:nucl-th/0505052]. [4] V. Koch and T. Schuster, Phys. Rev. C 81, 034910 (2010) [arXiv:0911.1160 [nucl-th]]. [5] B. I. Abelev et al. [STAR Collaboration], Phys. Rev. Lett. 103, 092301 (2009). [arXiv:0901.1795 [nucl-ex]]. 14 / 428 Jet studies in 200 GeV d+Au collisions from the STAR experiment at RHIC Jan Kapitan1 1 Nuclear Physics Institute ASCR Full jet reconstruction in heavy-ion collisions is a promising tool for the quantitative study of prop- erties of the dense medium produced in heavy-ion collisions at RHIC. Jet studies in d+Au collisions 142 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / are important to disentangle initial state nuclear effects from medium-induced kT broadening and jet quenching. We present inclusive jet pT spectra in d+Au collisions from the 2007-2008 RHIC run. We discuss correction for detector effects and underlying event background, including systematic uncertainties. These are dominated by the Jet Energy Scale, the uncertainty of which is decreased viaimproved detector response simulations. 27 / 430 Charged particle production√ with respect to the Reaction Plane in Pb-Pb collisions at sN N= 2.76 TeV Dong Jo Kim1 1 University of Jyväskylä The centrality dependence of nuclear modification factor(RAA) carries information about the path- length variation of partonic energy loss. However, the inclusive RAA for a given centrality emerges by averaging over different path lengths as the overlap zone of two colliding nuclei has typicallya nearly elliptical shape in the transverse plane. The partons traversing the medium in the in-plane di- rection are expected to lose less energy than out-of-plane, because they, on the average, have shorter path length inside the medium. In this sense, azimuthal dependence of RAA w.r.t. reaction plane offers to get a tighter constraint on the actual path length traversed by the parton inmedium. Recently we published a paper on the charged particle RAA[1], showing that the similar suppres- sion as RHIC energy is observed, and moreover a rising trend for increasing pT . Another interesting observation is the similarity of pT -differential elliptic flow at low pT between at RHIC and the LHC [2]. Since then, we have extended the pT reach for RAA with better precision and elliptic flow mea- surement up to 20 GeV /c with event plane, which allows us to study the path-length dependence of partonic energy loss with larger kinematic domain. We present the latest ALICE results from Pb-Pb collisions at sqrtsNN =2.76TeV on charged particle yields with respect to reaction plane angle as a function of centrality and transverse momentum. These results allow for a detailed examination of the influence of geometry in the collision region and of the interplay between collective flow and jet-quenching effects. [1] ALICE, K. Aamodt et al., Phys. Lett. B696, 30 (2011), 1012.1004. [2] ALICE Collaboration, K. Aamodt et al., Phys. Rev. Lett. 105, 252301 (2010). 105 / 431 Dilepton production in heavy-ion collisions within the parton hadron string dynamics (PHSD) transport approach Olena Linnyk1 Elena Bratkovskaya 2; Wolfgang Cassing 1 1 University of Giessen 2 FIAS, University Frankfurt am Main We describe heavy-ion collisions from the initial phase of colliding nuclei in their groundstates throughout the interaction phase up to the final hadronic elastic and inelastic interactions as well 143 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / as hadron decays using the nonequilibrium microscopic Parton-Hadron-String Dynamics (PHSD) transport approach, which includes the off-shell dynamics of quarks, antiquarks and gluons aswell as a covariant dynamical hadronization scheme in addition to the familiar (off-shell) hadronic reac- tion dynamics. Within PHSD the low mass dilepton sector (M<1 GeV) at SPS energies (measured by the NA60 and CERES Collaborations) is rather well described by hadronic degrees of freedom when a collisional broadening of the vector mesons (rho, omega) is incorporated; however, this no longer holds for higher masses. In the intermediate mass regime from 1 to 2 GeV, we find that the contribution from ‘massive’ q+qbar annihilation in the sQGP phase dominantes over the hadronic channels like pi+a1, pi+omega and rho+rho for In+In reactions at 160 A GeV. On the other hand, we find a quite different pattern of the dilepton production in Au+Au collisions at the topRHICenergy of sqrt(s)=200 GeV. Here the in-medium effects for the rho and omega vector mesons do not explain the large enhancement relative to p+p collisions observed in the invariant mass regime from 0.2 to 0.6 GeV by the PHENIX Collaboration. For masses above 1 GeV at RHIC energies, we find that the decay of open charm mesons together with the dilepton radiation from partonic interactions in the sQGP phase dominate the measured spectrum. 129 / 432 Deconfinement and chiral symmetry in effective models with fermions in higher representations Topi Kahara1 Kimmo Tuominen 1; Marco Ruggieri 2 1 Helsinki Institute of Physics 2 Yukawa Institute for Theoretical Physics We study the interaction between the chiral and deconfinement transitions using effective models such as the Polyakov extended linear sigma model and the Nambu-Jona-Lasinio model. In this talk we consider fermions in higher representations of both SU(2) and SU(3) gauge groups. Our results motivate further studies of these theories on the lattice and they are also relevant for models of electroweak symmetry breaking utilizing new strong dynamics, and their cosmological consequences. We find that for different fermion representations the qualitative and quantitative behaviour ofthe order parameters is compatible with the general expectations based on the global symmetries of the underlying theory. 28 / 433 Flow analysis with event-plane method using the VZERO detec- tor in Pb-Pb collisions at sqrt(sNN)=2.76 TeV collected by the AL- ICE experiment at the LHC Chang Beomsu1 1 ALICE Measurement of the azimuthal anisotropy of charged particles produced in heavy-ion collisions is one of the most powerful tools to study the properties of QCD Matter. √ An analysis of charged hadron flow in Pb-Pb data taken by the ALICE experiment at sNN =2.76 TeV will be discussed. The event plane [1] was reconstructed using the VZERO detector (two scintillator arrays covering pseudorapidity range 2.8 < η < 5.1 and −3.7 < η < −1.7) whose large pseudorapidity gap from the central tracking system (-0.8<η<0.8) helps to reduce non-flow contributions. 144 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Emphasize is given to the azimuthal anisotropy of charged particles, characterized by the Fourier coefficients, up to high transverse momenta. [1] A. M. Poskanzer and S. A. Voloshin, Physical Review C 58, 1671-1678 (1998). 153 / 434 Pion production in p+p and p+C interactions at 31 GeV/c Antoni Aduszkiewicz1 1 Faculty of Physics, University of Warsaw Evidence for the onset of deconfinement in central Pb+Pb collisions was reported by NA49 atthe CERN SPS at collision energy 30A GeV. This observation motivated the NA61/SHINE ion program which, in particular, aims to study properties of the onset of deconfinement by measurements of hadron production in p+p, p+A and nucleus-nucleus collisions at the SPS energies. The program started in 2009 when the on p+p interactions at 20, 31, 40, 80, and 158 GeV/c were recorded. This contribution presents preliminary spectra of negatively charged pions produced in p+pand p+C interactions at 31 GeV/c. The NA61 results will be compared with the corresponding NA49 data from central Pb+Pb collisions at this energy. Finally, the dependence of pion yield on reaction type at 31A GeV/c (NA61 and NA49 results) and 158A GeV/c (NA49 results) will be compared and discussed. 97 / 435 Distortion of photon HBT image by the vacuum birefringence in strong magnetic field Koichi Hattori1 Kazunori Itakura 1 1 High Energy Accelerator Research Organization (KEK) The experiment by the ultrarelativistic heavy ion collisions has opened a novel insight intotheex- treme state of matter. Besides, it provides an opportunity to study the dynamics of strong Abelian and non-Abelian gauge fields. In peripheral collisions, an extremely strong Abelian magnetic field is created by two colliding heavy ions having large electric charges. The magnetic field has a much greater order of magnitude than those of ever observed astronomical objects. Such a strong magnetic field becomes not only the source of an exotic phenomenon called the chiral magnetic effect but also a background field which allows for nonlinear QED phenomena, where the strong magnetic field interacts with photons emitted in the early stages of time evolutionof the created matter. Even though photon self-interaction is diagrammatically a higher order process with a number of external photon legs intermediated by an electron loop, extraordinarily strong magnitude of the background magnetic field compensates the smallness of the coupling constant, and leads to intriguing nonperturbative effects. The interaction causes a modification of production and propagation of photon, which results in significant effects on the observable photon spectrum. It was discussed recently that the presence of magnetic fields also allows for the decay of a real photon into a particle-antiparticle (lepton, or quark) pair, yielding an elliptic flow of observed photons [1]. 145 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The study of such nonlinear QED phenomena provides a prevision of planned photon detection in the LHC experiment. In this contribution, we examine the effect of the interaction, between an emitted photon andthe background magnetic field, on Hanbury Brown and Twiss (HBT) interferometry. Recently, oneof the authors investigated effects of the hadronic final state mean field interaction on the pion interfer- ometry in the central collisions [2,3]. We have found therein that the HBT images are distorted due to the phase shift of the pion amplitude propagating through the one-body mean field interaction region, which is computed by using the semi-classical approximation. The analysis was done on the basis of an analogue of eikonal approximation in the geometrical optics. In the present work, we incorporate the interaction of photon with the background magnetic field as a deviation of the re- fraction index from the unity, wherein the analogue is more evident. While the HBT interferometry by a photon pair is more promisingly accessible to the primordial image of the created matter than that by a pion pair, we have to take into account the distortion of image by the strong magnetic field. The refraction index of the vacuum in the presence of the magnetic field is obtained by incorporating the self-energy of photon, resummed with respect to the number of external photon legs, into the equation of motion for the Abelian gauge field. Depending on the two physical propagating modes of photon, two distinct refraction indices, called the vacuum birefringence, are obtained. Calculat- ing the optical-path-length of the photon specified by the refraction indices, we have the images distorted depending on the helicity of photons. In addition to the conventionally discussed three HBT parameters, e.g. outward, sideward and longitudinal radii, we investigate the distortion of the outward-sideward cross parameter, which indicates the azimuthal-angle dependence of the image in the non-central collisions [4]. The magnitude of the distortion also depends on the azimuthal angle because the presence of the magnetic field provides a preferred orientation. We show how and to what extent the elliptic shape of the original image is distorted depending on the magnitude of momentum, helicity and azimuthal angle. [1] K. Tuchin, Phys. Rev. C 83, (2011), 017901 [2] K. Hattori, T. Matsui, Prog. Theor. Phys. 122, (2010), 1301-1310. [3] K. Hattori, Prog. Theor. Phys. 124 (2010), 869-909. [4] M. Lisa, U. Heinz and U. Wiedemann, Phys. Lett. B 489,(2000), 287-292. 29 / 436 Identified particle v3 measurements at 200GeV Au+Au collisions at RHIC-PHENIX experiment Sanshiro Mizuno1 1 Graduate School of Pure and Applied Sciences-University of Tsuku Particle species dependence of transverse momentum distribution as well as elliptic event anisotropy v2 have been beautifully described by hydrodynamic model calculation in terms of radial and elliptic collective expansion in high energy heavy ion collisions. Initial participant position fluctuation is also suggested as a source of triangular initial geometry, which could then expand collectively to form the final triangular event anisotropy v3 in momentum space. The first v3 measurements of identified particles at 200GeV Au+Au collisions from RHIC-PHENIX experiment will be presented. The collective triangular expansion behavior seen in v3 will be compared with hydro-dynamic model expectation in order to understand possible differences or similarities from the radial and elliptic expansion. 437 146 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Upgrade of ALICE Electromagnetic Calorimeter to enhance di-jet measurements Shintaro Kubota1 1 Graduate School of Pure and Applied Sciences-University of Tsukuba Back-to-back jet produced by hard parton scatterings (di-jet) is an unique and powerful probe to quantify the properties of Quark Gluon Plasma at LHC. In the ALICE experiment, the electromagnetic calorimeter (EMCal) provides a crucial role to reconstruct jets with a good energy resolution, together with the information by Time Projection Chamber (TPC). In order to enhance the capability of back-to-back jet identification and yields of jets, photons, π0 and their correlations, we are constructing an additional electromagnetic calorimeter, called DCal (Di-jet Calorimeter) in ALICE. DCal has the same design of EMCal, but it will be placed on the opposite side of the EMCal in azimuth at mid-rapidity −0.7η0.7, together with the Photon Spectrometer (PHOS). In this poster, we present the physics cases of DCal by using simulation data, especially on jets, di-jets, hadron(π0)-jets measurements. The current status and plan of the DCal construction, and future perspectives will beshown. Global and collective dynamics / 438 Pseudorapidity dependence of charged hadron multiplicity and transverse energy densities in PbPb collisions from CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] The pseudorapidity and centrality dependence of transverse energy and charged particle multiplic- ities offers insight into the properties of the matter produced in the collisions of ultra-relativistic heavy nuclei. Multiplicities as a function of center-of-mass energy and collision centrality are im- portant for exploring the role of hard and soft scattering in particle production and for looking at novel effects in nucleus-nucleus collisions (e.g. scaling, saturation). Measurements of the charged hadron multiplicity and transverse energy are presented for minimum bias PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. The number of charged hadrons was obtained by two different methods based on the inner silicon pixel system oftheCMS detector at the LHC. One technique involved counting the number of reconstructed single particle hits in the pixel detector, while the other formed hit pairs (’tracklets’) from the different detector layers. The two methods are in excellent agreement. For the transverse energy measurement, CMS has almost hermetic calorimetry coverage with fine granularity and excellent resolution. In addition for particles near central rapidity momenta from the tracker can be combined with the calorimeter data to give a significant improvement of the system resolution. The measurements is compared with heavy-ion results from earlier experiments, where a smooth dependence on the collision energy is observed. The results as a function of centrality are compared to the corresponding valueinpp collisions interpolated from existing CMS measurements Global and collective dynamics / 439 147 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Charged hadron azimuthal anisotropy (v_2) in sqrtsNN = 2.76 TeV PbPb collisions from CMS During the past decade, azimuthal correlation measurements have played a pivotal role in our un- derstanding of the properties of high density QCD matter through their sensitivity to the early stage evolution of relativistic heavy-ion collisions. Despite our increased understanding of the transport coefficients of the plasma produced in these collisions, there remain many questions concerning the interplay between initial state conditions, the equation of state, and the evolution of the system through the final hadronization stage. Detailed experimental data obtained for the energy regime accessible using the LHC should help in establishing the shear viscosity to entropy ratio achieved in the produced, strongly interacting matter. The CMS experiment has measured the anisotropy parameter, v2, using four different methods: the event-plane, two or four particle cumulants, and Lee-Yang Zeros. Consistent results are found for the different methods after considering their respec- tive sensitivities to non-flow correlations and event-by-event fluctuations in the initial conditions. The anisotropy is studied as a function of transverse momentum, pseudorapidity and centrality ina broad kinematic range: 0.3 < pT < 12.0GeV/c, |η| < 2.4, and in 12 centrality classes in the range 0-80\%. The scaling of v2 with participant eccentricity and transverse particle density is examined and compared to lower energy results. Electromagnetic probes / 440 Weak boson production measured in PbPb and pp by CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] The unprecedented centre-of-mass energy available at the LHC offers unique opportunities forstudy- ing the properties of the strongly-interacting QCD matter created in PbPb collisions at extreme tem- peratures and very low parton momentum fractions. With its high precision, large acceptance for tracking and calorimetry, and a trigger scheme that allows the analysis of almost each minimum bias PbPb event by the high-level trigger, CMS is fully equipped to measure muons and electrons in the high multiplicity environment of nucleus-nucleus collisions. Electroweak boson production is an important benchmark process at hadron colliders. Precise measurements of Z production in heavy-ion collisions can help to constrain nuclear PDFs as well as serve as a standard candle of the initial state in PbPb collisions at the LHC energies. The inclusive and differential measurements of the Z boson yield in the muon decay channel will be presented, establishing that no modification is observed with respect to next-to-leading order pQCD calculations, scaled by the number of incoher- ent nucleon-nucleon collisions. The status of the Z measurement in the electron decay channel, as well as the first observation of W→μν in heavy ion collisions will be given. The heavy-ion results will be presented in the context of those obtained in pp collisions with the CMS detector. Jets / 441 Centrality and transverse momentum dependence of the nuclear modification of charged particle spectra in PbPb collisions at2.76 TeV from CMS Collaboration CMS1 1 UCLouvain 148 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / [email protected], [email protected] The nuclear modification factor R_AA is one of the key signatures for the energy loss of fastpartons traversing a QCD medium. Charged particle transverse momentum (pT) spectra have been measured by CMS for pp collisions at sqrt(s)=0.9 and 7 TeV, corresponding to integrated luminosities of 231 ub- 1 and 2.96 pb-1, respectively. Calorimeter-based high-transverse-energy jet triggers are employed to enhance the statistical reach of the high-pT measurements. The results are compared to various generator tunes and also to an empirical scaling of different collision energies with xT=2pT/sqrt(s) over the pT range up to 200 GeV/c. Using a combination of xT scaling and direct interpolation at fixed pT, a reference pT spectrum at sqrt(s)=2.76 TeV is constructed from pT = 1-100 GeV/c withless than 13% systematic uncertainty. We have obtained R_AA in bins of collision centrality for a PbPb data sample with an integrated luminosity of 7 ub-1, dividing by the interpolated reference spectrum. As seen at lower energies, the charged particle spectrum in central PbPb collisions is suppressed by at least a factor of five (R_AA < 0.2) compared to binary scaling around pT = 5-10 GeV/c. Above pT = 10 GeV/c, however, there is a significant rise in the nuclear modification factor, which willbe presented out to pT = 80 GeV/c. Electromagnetic probes / 442 Measurement of inclusive isolated photons in PbPb collisions with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] In studies of the dense medium produced in ultra-relativistic heavy ion collisions, photons are im- portant hard probes, since they are not expected to be modified by the medium. The measurement of isolated prompt photon production in PbPb collisions provides a test of perturbative quantum chro- modynamics (pQCD) and the information to constrain the nuclear parton distribution functions. CMS has shown excellent isolation capabilities in pp collisions at the LHC using the shower shape method. In heavy-ion collisions, two independent methods, shower shape and isolation, are used to separate isolated photons from non-prompt photons. This is the first application of these pp photon isolation techniques in heavy ion collisions. Shower shape templates are created with studies of the response in the electromagnetic calorimeter. The latter method, based on the tracker and the calorimeter, is found to have consistent results with the former method. We report the first measurement of the transverse momentum spectra of isolated photons in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon nucleon pair with the CMS detector. The results are compared to NLO calculations at an energy of 2.76 TeV. The centrality dependence of the nuclear modification factor will be reported for isolated prompt photons with pT from 20 GeV/c to more than 80 GeV/c. 30 / 443 Rapidity and centrality dependence of transverse energy distri- butions in PbPb collisions from CMS Collaboration CMS1 1 UCLouvain 149 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Transverse energy measurements offer insight into the dynamics of heavy ion collisions andthe total entropy created. At very forward angles they may also be sensitive to the low momentum components of the nuclear wave-function. CMS has almost hermetic calorimetry coverage with fine granularity and excellent resolution. In addition for particles near central rapidity momenta from the tracker can be combined with the calorimeter data to give a significant improvement of the system resolution. In this talk the transverse energy measurements from 2.76 TeV PbPb collisions as a function of centrality will be compared to similar CMS results from pp collisions and to our recently published multiplicity results. The pseudo rapidity dependence of the transverse energy per participant is susceptible to the longitudinal expansion of the system. This quantity has not been measured for truly heavy ions for centre of mass energies above 8 GeV. The width of this distribution grows slowly with centrality. At central rapidity the transverse energy per participant is above predictions based on lower energy data that assumed a logarithmic scaling with centre of mass energy. Jets / 444 Study of jet quenching using dijets in PbPb Collisions with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] Jets are an important tool to probe the hot, dense medium that is produced in ultra-relativistic heavy ion collisions. The large collision energy at the LHC provides copious production of dijets withen- ergies that can be cleanly identified above the heavy ion background. The multipurpose Compact Muon Solenoid (CMS) detector is well designed to measure these hard scattering processes with its high resolution calorimeters and high precision silicon tracker. Jet quenching was observed by a significant imbalance of dijet transverse momentum in PbPb collisions at a center-of-mass energyof = 2.76 TeV. The fraction of unbalanced dijets is found to increase strongly with increasing collision centrality. The dijet imbalance persists to the highest jet momenta studied, while angular distribu- tions are only weakly modified. The redistribution of the quenched jet energy was studied usingthe transverse momentum balance of charged tracks projected onto the direction of the leading jet. In contrast to pp collisions, a large fraction of the momentum balance for asymmetric jets is found to be carried by low momentum particles at large angular distance to the jet axis. Jets / 445 Dijet fragmentation functions measured in PbPb collisions with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] The energy loss of fast partons traversing the strongly interacting matter produced in high-energy nuclear collisions is one of the most interesting observables to probe the nature of the produced medium. Analyzing data from PbPb collisions at a center-of-mass energy of 2.76 TeV, recorded with the Compact Muon Solenoid (CMS) detector, parton energy loss is observed as a significant imbalance of dijet transverse momentum. To gain further understanding of the parton energy loss mechanism and how it manifests itself in the distribution of final state particles, parton fragmen- tation functions are studied for the leading and subleading jet in bins of centrality and dijet imbal- ance. 150 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Dijets are reconstructed using the anti-kT jet algorithm, with the particle flow method of event reconstruction. Particle flow, which is applied to heavy-ion collisions for the first time inthismea- surement, allows for improved jet reconstruction by combining track and calorimeter information at the particle level. The fragmentation functions for leading and subleading jets are compared to model calculations and measurements in pp collisions. The results confirm and complement earlier CMS results based on calorimeter jets and yield a detailed picture of parton propagation in the hot QCD medium. 154 / 446 The dynamics of quark droplets Johan Jannik Bjerrum-Bohr1 1 FIAS Frankfurt Institute for Advanced study Relativistic heavy-ion collisions represent a practical way to produce Quark-Gluon Plasma in the laboratory. The hydrodynamical model is widely used to describe the evolution of the Quark-Gluon Plasma as a continuous fluid. It has been predicted that in the course of fast expansion thisfluid will split into many droplets which later on evolve by evaporating hadrons from the surface. I will present a simple model of a quark droplet based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure, surface tension and hadron emission. Examples of numerical simulations will be presented. Jets / 447 Monte-Carlo simulation for elastic energy loss of high-energy partons in a hydrodynamical background Jussi Auvinen1 Hannu Holopainen 1; Kari Eskola 1; Thorsten Renk 1 1 University of Jyväskylä We examine the significance of elastic collisions as the suppression mechanism of high-energy par- tons in the strongly interacting medium formed in ultrarelativistic heavy ion collisions. For this purpose, we have developed a Monte Carlo simulation describing the interactions of perturbatively produced, non-eikonally propagating high-energy partons with the quarks and gluons from the ex- panding QCD medium. The partonic collision rates are computed in leading-order perturbative QCD, while three different hydrodynamical scenarios are used to model the QCD medium: (1+1)- dimensional hydro with initial conditions from the EKRT model for central heavy ion collisions, (2+1)-dimensional hydro with a smooth sWN profile obtained from the optical Glauber model for non-central collisions, and event-by-event hydro with an eBC profile from the Monte Carlo Glauber model to study the initial state fluctuation effects. We compare our results with the neutral pion suppression observed in sqrt(s_NN)=200 GeV Au+Au collisions at the BNL-RHIC. We find the incoherent nature of elastic energy loss incompatible with the measured data. Also the effect of the initial state fluctuations appears to be negligible. Jets / 448 151 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Jet reconstruction with particle flow in heavy-ion collisions with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] In the particle-flow approach one attempts to combine information from all available sub-detector systems to reconstruct all stable particles. Such an event reconstruction has been shown to improve the resolution of jets and missing transverse energy in pp collisions compared to purely calorimetric measurements. This is achieved primarily by combining the precise momentum determination of charged hadrons in the silicon tracker with the associated energy depositions in the calorimeters. By resolving individual particles inside jets, particle flow reduces the sensitivity of the jet energy scale to the jet fragmentation pattern, which is one of the largest sources of systematic uncertainty in jet reconstruction. Particle flow is thus an attractive tool for the study of potential modifications to jet fragmentation in heavy-ion collisions. The particle flow algorithm has been adapted tothe heavy-ion environment. The performance of jet reconstruction from particle flow objects inPbPb collisions using the anti-kT jet reconstruction algorithm will be presented. Heavy flavors / 449 Charmonium production measured in PbPb and pp collisions by CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] CMS is fully equipped to measure hard probes in the di-muon decay channel in the high multiplicity environment of nucleus-nucleus collisions. Such probes are especially relevant for studying the quark gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. In particular, the Jψ production in heavy ion collisions has been studied at different energies and with different collision systems without yet giving a global picture thatisfully understood. Measuring the charmonium production at the LHC energies in PbPb collisions will help constraining predictions, in particular those expecting high recombination of prompt J/ jpsi√ s or suppression in hot medium. We will review CMS J/\psi measurements in pp collisions at sNN = 7~TeV, which allow precision studies of quarkonia production and serve as a reference for the observation of hot nuclear effects. CMS is able to distinguish non-prompt J/ψ from prompt J/ψ in PbPb collisions, and will present the prompt J/ψ production cross-section in PbPb inclusively and as a function of transverse momentum, rapidity and number of nucleons participating in the collision. Finally, we compare the B fraction measured in PbPb collisions with that measured in pp at various energies. Heavy flavor / 450 Bottomonium production measured in PbPb and pp collisions by CMS Collaboration CMS1 1 UCLouvain 152 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / [email protected], [email protected] The LHC centre-of-mass energy allows copious Υ production in PbPb collisions. Detailed measure- ments of bottomonium will help characterize the dense matter produced in heavy-ion collisions beyond what was accessible at RHIC (mostly) with charmonia. The full spectroscopy of quarko- nium states has been suggested as a possible thermometer for the QGP. With its excellent dimuon mass resolution, CMS has measured the three Υ states in pp collisions. With the 2010 PbPb data sample, CMS has observed the Υ. The Υ(1S) cross-section is presented as a function of transverse momentum, rapidity and centrality. Correlations and fluctuations / 451 Observation of a ridge correlation structure in high multiplicity pp collisions with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] Results on two-particle angular correlations are presented in proton-proton collisions at center of mass energies of 0.9, 2.36, 2.76 and 7 TeV, over a broad range of pseudorapidity and azimuthal angle. In very high multiplicity events at 7 TeV, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate pT of 1-3 GeV/c, in the kinematic region 2.0 < |∆η| < 4.8 and small \Delta\Phi. This structure, which has not been observed in pp collisions before, is similar to what is known as the “ridge” in heavy ion collisions. It is not predicted by commonly used proton-proton Monte Carlo models and is not seen in lower multiplicity pp collisions. Updated studies of this new effect as a function of particle transverse momentum, rapidity andevent characteristics are shown and discussed in comparison to various model calculations. Correlations and fluctuations / 452 √ Dihadron correlations in PbPb collisions at sNN = 2.76 TeV with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] Measurements of charged dihadron correlations from the CMS collaboration are presented for PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair over a broad range of pseudora- pidity and the full range of azimuthal angle. With its large pseudorapidity coverage (|η|<2.4), the CMS tracker is ideally suited for detailed analyses of both short and long-range charged hadron cor- relations at the LHC. For the most central 0-5\% collisions, a broadening of the away side (∆ϕ > 1) dihadron correlation is observed at all ∆η when compared to pp collisions. A significant correlated yield is observed for pairs of particles with small ∆ϕ but large longitudinal separation ∆η, com- monly known as the “ridge”. The ridge persists up to at least |∆η| = 4 and its effect is found to be stronger than what was previously observed at RHIC. The dependence of the ridge region shape and yield on transverse momentum and collision centrality has been measured. For particles of transverse momentum of 2–4 GeV/c, the ridge is found to be the most prominent when correlated to particles of 2–6 GeV/c, but disappears when correlated to 8–10 GeV/c particles. A Fourier analysis of the long-range two-particle correlations will be presented and discussed in the context of CMS measurements of higher order flow coefficients. 153 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 31 / 453 Measurement√ of higher order flow harmonics in PbPb collisions at sNN = 2.76 TeV by CMS Collaboration CMS1 1 UCLouvain Collective flow is an important probe of the earliest stages in the expansion of the hotanddense matter created in relativistic heavy-ion collisions. Higher harmonics of the azimuthal distribution of emitted particles, in particular v3 and v4, complement v2 measurements in elucidating the dy- namical evolution of the bulk medium and providing constraints on its transport properties. With its large acceptance and broad rapidity coverage, the CMS detector is ideally suited to provide de- tailed analyses of higher√ order harmonic flow at the LHC. Measurements of vn (n = 3 to n = 6) in PbPb collisions at sNN = 2.76 TeV using the cumulant and Lee-Yang zeros methods will be pre- sented as a function of pT and centrality. The scaling of the higher order flow harmonics with initial 2 participant eccentricity and the ratios of the flow harmonics, such as v4/v2, will be explored and discussed. 106 / 454 Electron reconstruction and Z measurement in the di-electron channel in PbPb collisions with CMS Collaboration CMS1 1 UCLouvain We report on the measurement of Z boson production and decay in the di-electron channel in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV by the CMS experiment at the LHC. We observe about 30 events containing a pair of electrons which were reconstructed to form distinctive Z boson candidates. Z boson reconstruction in the electron channel is challenging due to the complexity of electron re- construction in the high-occupancy environment of heavy-ion (HI) collisions. The reconstruction of electrons in CMS uses information from the pixel detector, the silicon strip tracker and the elec- tromagnetic calorimeter (ECAL). The measurement of electron energy in the ECAL is degraded by the significant tracker material in front of the calorimeter, and by the presence of a strong magnetic field aligned with the beam axis, giving an azimuthal spread of electromagnetic clusters withinthe ECAL. Despite this challenging reconstruction environment, we are able to reconstruct electrons with dedicated heavy ion tracking and tuned clustering algorithms. The performance of electron reconstruction in Pb-Pb collisions is presented. In particular, the Z measurement in the di-electron channel is presented as a first observation and a main result of electron reconstruction in HIcolli- sions. 64 / 455 √ Study of beauty production in pp collisions at s = 7 TeV with ALICE, using displaced electrons Min Jung Kweon1 1 Ruprecht-Karls-Universitaet Heidelberg 154 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The measurement of single electrons from heavy flavored hadron decays at RHIC indicates strong coupling of heavy quarks to the medium produced in ultra relativistic heavy-ion collisions. At the LHC, heavy quarks are copiously produced. This will allow us to investigate the heavy quark energy loss mechanism in detail and even its quark mass dependence in the medium produced by heavy- ion collisions. Moreover, the measurement of heavy quark production in pp collisions provides an important test of pQCD calculation and serves as a baseline for studies in heavy-ion collisions. The beauty quark cross section can be measured by preferentially selecting√ the electrons from beauty hadron decays via displaced vertices. In 2010, pp collisions at s = 7 TeV have been recorded by ALICE at the LHC. We report on the status of the analysis for the measurement of the pT differential cross section of electrons from beauty hadron decays at mid-rapidity in pp collisions. 137 / 456 Readout of the CMS experiment during the 2010 heavy ion run CMS was designed and optimized to record high luminosity pp collisions. Its powerful DAQ and trigger systems are normally configured to handle very high frequency of relatively low multiplic- ity pp events. To reduce data volume the CMS sub-detectors are read out using zero suppression algorithms optimized for pp. The large multiplicities expected in PbPb collisions required a different optimization ofthezero suppression algorithms. The optimization could only be done after the data was taken. Tomake sure that the collected data is of highest quality the CMS collaboration decided to disable the zero suppression algorithms for the silicon strip tracker and the electromagnetic and hadron calorimeters for the duration of the first PbPb run. This resulted in event size of about 12MB of data, corresponding to about 11 million channels recorded for each event. CMS was recording data at up to 180 Hz and with a bandwidth to tape of over 2GB/s, well beyond of what it was designed for (more than 6 times the data volume per second recorded during the pp running). The excellent luminosity delivered by the LHC required that CMS trigger system reduces therateof minimum bias events written to tape while maintaining the rate of interesting physics events. The trigger algorithms operating at Level-1 and High Level Trigger were optimized to provide maximum selectivity and data writing rates for jets, muons and photons. The fraction of minimum bias events was adjusted during running to maximize the available bandwidth. In just few weeks CMS collected about 890 TB of data. After the run was over, CMS developed anew zero suppression algorithms optimized for heavy ions and the data was compressed offline to about 190TB. In this talk we will present the CMS configuration during the 2010 PbPb run, describe the detailed performance of the CMS DAQ and trigger system and the subsequent offline compression process- ing. 138 / 457 Performance of the CMS Zero Degree Calorimeter for PbPb and pp running Collaboration CMS1 1 UCLouvain 155 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The two CMS Zero Degree Calorimeters have been designed to measure and trigger onphotons and neutrons produced in pp and heavy ion collisions. Their trigger rate is proportional to the luminosity and can be used as a measure of beam quality. Augmented by scintillators they can also give a measure of the luminous region and its growth during the store. By measuring the horizontal distribution of electromagnetic clusters they give a measure of the beam crossing angle at CMS. We will present their performance in test beams and in measuring the neutron spectra produced by PbPb collisions. Finally their utility in measuring centrality will be presented. 65 / 458 B → J/ψ measurement in PbPb at √s_NN = 2.76 TeV using CMS Collaboration CMS1 1 UCLouvain [email protected] √ Measuring open heavy flavor at (sNN ) = 2.76~TeV will test the theoretical calculations on the J/ψ suppression at RHIC compared to LHC. With the CMS high resolution tracking, we are able to separate prompt J/ψ from non-prompt J/ψ in heavy ion collisions, thus disentangling yield modifi- cations on primary J\ψ from those coming from Bs that decay outside the medium. The long life-time of the b-hadron determines his decay products to be produced further away from the primary ver- tex. This makes possible the separation of the prompt from the non-prompt J/ψ based on their dis- tance to the primary vertex. To determine the fraction of non-prompt J/ψ from b-hadron decays in data, we performed a 2D unbinned maximum-likelihood fit in mass and pseudo-proper decay length, binned in transverse momentum, rapidity and centrality bins. This poster presents the first measure- ment of the prompt and non-prompt J/ψ production in the di-muon√ decay channel as a function of transverse momentum, rapidity and centrality in PbPb collisions at sNN = 2.76~TeV. 66 / 459 Data-driven efficiencies for di-muon measurements in heavy ion collisions with CMS Collaboration CMS1 1 UCLouvain [email protected] √ CMS has been collecting single muon triggered data in 2010 at sNN = 2.76~TeV in PbPb in order to extract from real data efficiency corrections for muon based analysis. These results were usedas an important cross-check for the Monte-Carlo based efficiency corrections used for the Z boson and quarkonia analysis in PbPb and taken into account in the systematics. This poster will review this {\it Tag and Probe} technique that is used for the data-driven measurement of muon efficiencies in CMS on PbPb data. Results obtained on data are compared to what is measured on Monte-Carlo. 67 / 460 Effect of the polarization on the acceptance for quarkonia studies in PbPb at √sNN = 2.76 TeV in CMS 156 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Collaboration CMS1 1 UCLouvain Measuring J/ψ polarization in heavy ion collisions requires a very high luminosity. While most of the LHC experiments have been quoting corrected yields in heavy ion collisions based on the assumption of an unpolarized production, CMS prefers to quote results in different scenarios, allow- ing theorists to confront their√ calculations in the frame they prefer. The effect of polarization on the acceptance of quarkonia at sNN = 2.76~TeV will be discussed in this poster. The final quarkonia corrected yields measured by CMS in PbPb collisions for 5 different polarization scenarios will be reviewed. 107 / 461 Performance of PHENIX HBD in Au + Au central collisions Yosuke Watanabe1 1 Tokyo University The PHENIX experiment observed a large enhancement of electron-positron pairs in the invariant mass range of 0.2 to 0.5 GeV/c^2 in Au+Au collisions at sqrt(s_NN)=200 GeV. However, it is difficult to draw a firm physics conclusion from the measurement, since the measurement still has large statistical and systematic uncertainties.The main uncertainty comes from the small signal-to-background ratio of about 1/200 in minimum bias collisions. The electron decay branching ratios of light vector mesons are very small (~10^{-4}), while there are many background electrons mainly originating from pi^0 Dalitz decays and gamma conversions. A Hadron Blind Detector,(HBD) has been installed in the PHENIX to reject such background electrons using the opening angle information of electron positron pairs, since the opening angle of electron positron pairs from those decays is small compared to the pairs from light vector mesons. PHENIX has successfully collected p+p and Au+Au data with the HBD in 2009 and 2010. In Au+Au central collisions, high occupancy of HBD readout pads needs to be handled. The high occupancy is mainly due to the scintillation light emitted by CF4, which is the Cherenkov radiator gas of the HBD. In Au+Au peripheral collisions or p+p collisions, the effect of scintillation light is negligible compared to the Cherenkov light by electrons. However, in Au+Au central collisions, the number of charged particles is so large that the effect of scintillation lights becomes significant. In this poster, details of the analysis scheme to handle this situation will be presented and current performance of HBD in di-electron measurements will be reported. 68 / 462 Quarkonia propagation and collectivity in the QGP: Towards the suppression of quarkonia suppression Hamza Berrehrah1 Joerg Aichelin 1; Pol Bernard Gossiaux 1 157 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Subatech For 20 years, the suppression of quarkonia has been studied as a probe of the quark gluon plasma (QGP) properties, either by Debye screening of the interaction between the q-qbar pair (Matsui and Satz) or via gluo-dissociation of quarkonia states, which remain strongly bound (Kharzeev). How- ever, the comparison between experimental data and scenarios including suppression mechanisms is not very conclusive. Rather than focusing only on these “suppressed” quarkonia, an alternative track is to focus not only on the suppressed but also on the physical properties of quarkonia survivors in the QGP. In fact, recent results from NA50 and NA60 experiments at SPS showed that these quarkonia indeed carry a non-zero elliptic flow. This could lead to a reconsideration of the propagation and collectivity of these quarkonia in the QGP, especially the elastic scattering process of quarkonia states with the partons in the QGP. We study the quarkonia propagation and collectivity by using a hydrodynamic transport code. This code requires the evaluation of two ingredients: The elastic cross section and the Fokker-Planck (FP) coefficients for stochastic processes (drag and diffusion coefficients). In my contribution, I will first present some theoretical calculations and results obtained forthe elastic cross section, following perturbative calculations in quantum mechanics and in QCD. I will then present our model for the estimation of FP coefficients and discuss the collisional energy loss of quarkonia in the QGP. Finally, results deduced from our transport code MC@SHQ to study the quarkonia propagation and collectivity are shown. The general tendency of our results shows that quarkonia elastic processes have non-negligible influence on the quarkonia study in the QGP. Future facilities and experiment upgrades / 464 ALICE detector upgrades Thomas Peitzmann1 1 Universiteit Utrecht The ALICE experiment is specifically designed for the study of strongly interacting matter ascreated in heavy ion collisions at LHC. With some of its particular features, like the very good measurement of low momentum particles and the particle identification capabilities it also provides unique mea- surements in p+p collisions. However, very recent developments in heavy ion physics suggest that some more enhanced measurement capabilities will be strongly desirable to obtain a deeper under- standing of the new matter created. ALICE is setting up a program of detector upgrades, which could to a large extent be installedin the long LHC shutdown foreseen for 2017/18, to address these new scientific challenges. Projects considered include an upgrade of the inner tracking system (ITS), the installation of a new forward calorimeter (FOCAL), the extension of the muon spectrometer (MFT, muon forward tracker), the installation of a detector with enhanced particle identification at high momentum (VHMPID), and additional detectors enhancing the capabilities for diffractive physics (AD = ALICE Diffractive). An increased rate capability of the largest detector in ALICE, the time projection chamber (TPC), is also under investigation, and it is foreseen to improve the data acquisition and high level trigger systems (DAQ & HLT) to achieve more bandwidth and to use more sophisticated and complex triggers. We will discuss the scientific frontiers and will present the corresponding upgrade projects under study for the ALICE experiment. 160 / 466 Large-N_c behavior of hadronic models at nonzero temperature 158 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Achim Heinz1 Dirk Rischke 1; Franesco Giacosa 1 1 ITP Frankfurt am Main Effective hadronic models have been widely used to describe the chiral phase transition. In this work we study the behavior of the critical temperature T_c for the restoration of chiral symmetry as function of the number N_c of colors. We find that T_c increases with Sqrt[N_c]; this scaling contradicts the basic expectations for the chiral phase transition which, just as the deconfinement phase transition, should be independent of N_c. Indeed, in chiral models with quark degrees of freedom T_c scales as N_c^0, as expected. We have modified a hadronic linear sigma model by including a temperature-dependent coupling constant in such a way that the expected large-N_c scaling is recovered. Consequences for the phase diagram are investigated. Finally, we have coupled the linear sigma model to a Polyakov loop in such a way that the chiral phase transition is triggered by the deconfinement phase transition. Also in this case the correct large-N_c results are recovered. 139 / 467 Construction and Installation of the PHENIX silicon pixel vertex tracker Takashi Hachiya1 1 RIKEN A silicon vertex tracker (VTX) is one of the upgrade programs in the PHENIX experiment to measure the production of heavy (charm and bottom) quarks in Au+Au and polarized p+p collisions. The production of heavy quarks is a powerful tool to study both the properties of a dense partonic matter created in high energy heavy ion collisions and the gluon contribution to the spin structure of proton in polarized p+p collisions. The VTX provides the precise measurement of heavy flavors and a clear separation of charm and bottom contributions. The VTX comprises the four layers of the barrel detectors. The two inner layers consist of silicon pixel detectors and the two outer layers consist of silicon stripixel detectors. The VTX was constructed and installed during the shutdown period of year 2010. In this poster presentation, we report the details of the VTX construction and installation. 78 / 468 Forward and Backward√ to Mid-Rapidity Correlations Measured in d+Au Collsions at SNN = 200 GeV with the PHENIX Detec- tor 159 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Zvi Citron1 1 Weizmann Institute of Science Deuteron-gold collisions offer insights into the nuclear structure function and a valuable baseline for Au+Au collisions. The d+Au system provides the opportunity to probe the gluonic structure of the Au nucleus. There are strong theoretical and experimental interests in the possibility ofgluon saturation effects influencing parton distributions at very low x in the nucleon. This effect would be even stronger in a nucleus and can be investigated via d+Au collisions by measuring forward rapidity, d-going side, particles. By contrast the higher x region of Au nucleus may be examined through measurements of the backward rapidity, Au-going side, particles. Comparison of the mid- rapidity yield and widths correlated with jets triggered on the d going side and those correlated with jets triggered on the Au going side, allows the exploration of gluon saturation and other x dependent effects. Hadron thermodynamics and chemistry / 469 Particle identification in the ALICE experiment Alexander Philipp Kalweit1 1 Technische Universität Darmstadt The particle identification capabilities of the ALICE experiment are unique among the fourmajor LHC experiments. The working principles, the strategies for signal extraction, and excellent per- formance of the central barrel detectors in a high-multiplicity environment will be presented. The particle identification of the Inner Tracking System (ITS) and the Time Projection Chamber (TPC)are based on the specific energy loss whereas the Time-Of-Flight detector (TOF) determines the particle velocity by measuring its flight time. Thus low momenta charged kaons, pions, protons, deuterons, tritons, helium-nuclei, and their respective anti-particles can be identified from 100 MeV/c upto several GeV/c in momentum and the corresponding spectra and yields can be extracted. Weak de- cays of strange particles can be identified via their particular kink and V0 topologies and the precise determination of the first and secondary vertices. The pT-reach of hadron identification canbeex- tended using Cherenkov-radiation in the High Momentum Particle Identification detector (HMPID) and by the relativistic rise in the ionization measurement of the TPC. Electron identification at higher momenta is achieved by the detection of transition radiation in the Transition Radiation Detector (TRD). 155 / 470 U(1)A anomaly effects on phase diagrams in chiral random ma- trix model Takashi Sano1 Hirotsugu Fujii 1 1 University of Tokyo Incorporating the background instanton effects, we extend the chiral random matrix model to include the anomaly effect. 160 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The anomaly effect appears naturally as the flavor mixing determinant interaction terms, which are missed in the conventional random matrix models. Due to the determinant interaction terms, the model shows the second-order phase transition for two massless-quark flavors and the first-order for three light-quark flavors at finite temperatures. We investigate the phase diagram of this model at finite T/mu and furthermore at finite isospin and hypercharge chemical potentials. We find that the critical point exists on T-mu plane with physical quark masses. We also find that the determinant terms cause the mixing not only between the chiral condensates but also between the chiral and meson condensates, which results in an enlargement of the region where, for example, both of the pion and the strange-quark chiral condensates have finite values. The anomaly effects enrich the phase structure and we expect that this is also the case in QCD. References: Phys.Rev. D80 (2009) 034007. Phys.Rev. D81 (2010) 037502. Phys.Rev. D83 (2011) 014005. 108 / 471 The Level-0 trigger of the ALICE Electromagnetic Calorimeter Jiri Kral1 1 University of Jyvaskyla The trigger system of the ALICE Electromagnetic Calorimeter (EMCal) aims to enhance the selection of hard-QCD events containing high-p_{T} neutral particles and jets to be recorded. The EMCal shower (photon) trigger (level 0) entered in operation in 2010. The trigger implementation and level 0 decision algorithms will be presented with special focus on the tight timing requirements. Minimum bias data containing trigger decision information has been used for offline performance studies. The trigger performance results deduced from analysis of the minimum bias datasetand from the EMCal triggered data set taken in the p+p \sqrt{s}=2.76TeV run will be presented. Heavy flavors / 472 Charmonium spectral functions at finite momenta in the quark- gluon plasma from lattice QCD Chiho Nonaka1 Masakiyo Kitazawa 2; Masayuki Asakawa 2; Yasuhiro Kohno 2 1 Nagoya University 2 Osaka University From phenomenological considerations, J/psi suppression was proposed as a signature of QGP production in relativistic heavy ion collisions, and has been considered as one of the most promising ones [1]. 161 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / However recent lattice QCD calculations show that charmonia survive even above the critical temperature [2], which presents the possibility that the scenario of J/psi suppression in relativistic heavy ion collisions may change. To understand the relativistic heavy ion collision physics we need to take into account dynamics of the fireball which is produced after collisions. Therefore the detailed study on spectral functions of charmonia at finite momenta from the first principle calculation would shed light on the understanding of the J/psi suppression mechanism in relativistic heavy ion collisions. We study the charmonium spectral functions at finite momenta in the quark-gluon plasma on 64^3 × N_t(=96(T/Tc=0.78),54(1.38),46(1.62),40(1.87),32(2.33)) quenched anisotropic lattices with anisotropy a_s /a_t= 4, analyzing correlation functions of charmonia by the maximum entropy method (MEM) which is a very useful and powerful tool to analyze spectral functions from lattice QCD simulations [3]. We show detailed features of charmonium spectral functions of pseudoscalar and vector channels and modification of the dispersion relation at finite momenta and discuss medium effect on them inQGP. [1] T. Matsui and H. Satz, Phys. Lett. B 178 (1986) 416, T. Hashimoto, K. Hirose, T. Kanki and O. Miyamura, Phys. Rev. Lett. 57 (1986) 2123. [2] M. Asakawa and T. Hatsuda, Phys. Rev. Lett. 92 (2004) 012001, S. Datta, F. Karsch, P. Petreczky and I. Wetzorke, Phys. Rev. D 69 (2004) 094507, H. Iida, T. Doi, N. Ishii, H. Suganuma and K. Tsumura, Phys. Rev. D 74 (2006) 074502, T. Umeda, Phys. Rev. D 75 (2007) 094502. [3] M. Asakawa, T. Hatsuda and Y. Nakahara, Prog. Part. Nucl. Phys. 46 (2001) 459. 69 / 473 Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions at LHC Sascha Vogel1 Joerg Aichelin 1; Klaus Werner 1; Pol Bernard Gossiaux 1 1 Subatech One of the most promising probes to study deconfined matter created in high energy nuclear col- lisions at RHIC and LHC is the energy loss of (heavy) quarks. It has been shown in experiments at the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass, experience a remarkable stopping in the Quark Gluon Plasma. In this exploratory investigation we study the energy loss of heavy quarks in high multiplicity proton-proton collisions at LHC energies. Although the colliding systems are smaller than com- pared to those at RHIC (p+p vs. Au+Au) the higher energy leads to multiplicities comparable to Cu+Cu collisions at RHIC. The high energy densities reached in LHC collisions might create ade- confined state of matter even in elementary reactions. The interaction of heavy quarks withthis environment gives rise to a non-negligible suppression of high momentum heavy quarks in elemen- tary collisions. This probe will allow to further pin down the physical quantities of the phase transition totheQuark- Gluon-Plasma at LHC energies. S.Vogel, P.B.Gossiaux, K.Werner, J.Aichelin, ‘Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions atLHC’ currently being reviewed by PRL [arXiv:1012.0764 [hep-ph]]. Pre-equilibrium and initial state / 474 162 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Influence of tubular initial conditions on two-particle correlations Frederique Grassi1 Rone Andrade 1; Wei-Liang Qian 2; Yogiro Hama 1 1 Instituto de Fisica-Universidade de Sao Paulo 2 Departamento de Fısica-Universidade Federal de Ouro Preto Relativistic nuclear collisions data on two-particle correlations exhibit structures as function of rela- tive azimuthal angle and rapidity. A unified description of these near-side and awayside structures is proposed for low to moderate transverse momentum. It is based on the combined effect of tubular initial conditions and hydrodynamical expansion. A 3+1 hydrodynamic approach with fluctuating tubular initial conditions, in addition to reproducing both the near and away-side structures [1], leads to a good qualitative agreement with various data: dependence on trigger/associated particle tranverse momentum and on centrality [2], difference in the away-side structure for in-plane/out-of plane triggers [3]. Some results on the relation between triangularity and triangular flow have also been obtained for this approach [4]. Since 3+1 hydrodynamics is a complicated scenario, we have also studied the effect of single tubes in 2+1 hydrodynamics. Contrary to expectations, the hydrodynamic solution shows that the high energy density tubes (leftover from the initial particle interactions) give rise to particle emissionin two directions and this is what leads to the various structures [2], including the effect of in-plane/out- of plane triggers [3]. This description is sensitive to some of the initial tube parameters and may provide a probe of the strong interaction. [1] J. Takahashi, B.M. Tavares, W.L.Qian, R. Andrade, F. Grassi, Y. Hama, T. Kodama, N.Xu, Phys. Rev. Lett. 103 (2009) 242301 (arXiv:0902.4870), [2] R.P.G. Andrade, F. Grassi, Y. Hama,W.-L. Qian, Nucl.Phys. A854 (2011) 81 (arXiv:1008.0139), [3] ] R.P.G. Andrade, F. Grassi, Y. Hama, W.-L. Qian, work in progress, [4] F.G. Gardim, F. Grassi, Y. Hama, M. Luzum, J.-Y. Ollitrault, work in progress. 70 / 475 Using separated bottom and charm contribution to pin down the role of radiative energy loss for heavy quarks Sascha Vogel1 Joerg Aichelin 1; Pol Bernard Gossiaux 1; Sonia Kabana 1; Witold Borowski 1 1 Subatech One of the most promising probes to study deconfined matter created in high energy nuclear col- lisions at RHIC and LHC is the energy loss of (heavy) quarks. It has been shown in experiments at the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass, experience a remarkable medium suppression in the Quark Gluon Plasma. Although various features of heavy quark physics have been understood, several challenges remain. To further study the energy loss mechanism it is not only necessary to separate charm and bottom quarks but also to separate the two sources of energy loss, collisional or radiative energy loss. In this contribution we present a method for extracting the difference between collisional and radia- tive energy loss of heavy quarks. By analyzing separated bottom and charm contributions to the heavy quark spectrum one cangain information about the relative strength of radiative and collisional energy loss. 163 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / This talk will give a detailed explanation of how one can separate this information experimentally and what we can learn from this analysis with respect to heavy quark energy loss. By using existing experimental data we will constrain the parameter space of energy loss physics and rule out several model parametrizations. A systematic parameter check with regard to RHIC data is carried out and perspectives for RHIC upgrades and the LHC will be presented. Pre-equilibrium and initial state / 476 Particle multiplicities in high-energy hadronic collisions at RHIC/LHC from CGC with local rcBK evolution Hirotsugu Fujii1 Kazunori Itakura 2; Yasushi Nara 3; Yoshio Kitadono 2 1 University of Tokyo 2 KEK 3 Akita Int’l University A color glass condensate (CGC) model for particle productions at collider energies is confronted with the data at RHIC and LHC. When applying the CGC picture to high-energy scatterings at LHC (or higher) energies, we need to include the effects of the running coupling and the transverse expan- sion of the colliding hadrons. These two are appropriately incorporated here. Main features ofour model include 1) fluctuations of the transverse positions of the nucleons in the projectile, 2) the Gaussian shape for the transverse profile of a nucleon to account for the transverse expansion of the nucleon with increasing energy, and 3) the x-evolution of the unintegrated gluon distribution by the running-coupling Balitsky-Kovchegov (rcBK) equation which is applied locally in the impact parameter space. We study the influence of initial condition for rcBK equation on particle production in high energy hadronic collisions. Specif- ically, the initial conditions provided by i) the naive McLerran-Venugopalan (MV) model and ii) the running coupling MV model with adjustable parameters are examined. The use of running-coupling MV model as the initial condition isnec- essary for the consistency with the evolution equation which includes the effects of the running coupling. 477 Global characteristics, long-range correlations, ridge and fempto- scopic radii in pp-collisions at LHC Larisa Bravina1 Evgeny Zabrodin 2; Johannes Bleibel 3; Liudmila Malinina 2; Mads Stormo Nilsson 2 1 Department of Physics-University of Oslo-Unknown 2 Department of Physics, University of Oslo 3 Institut f\”ur Physik, Universit\”at Mainz, Multiplicity, rapidity and transverse momentum distributions of hadrons produced in inelastic and non-diffractive pp - collisions at energies from 200 GeV to 14 TeV are described within QuarkGluon 164 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / √ String Model. Good agreement with the available experimental data, including the LHC data at s = 7 TeV, is √obtained and predictions are made for the collisions at top LHC energy s = 14 TeV [1]. It is shown that within the examined energy range one cannot distinguish between the “standard” logarithmic dependence (∝ ln2 s) and novel power-law approximation (∝ Eλ), employed for particle densities and for their mean p_T in Regge theory and in theory of Color Glass Condensate, respectively. The model indicates that Feynman scaling and extended longitudinal scaling remain valid in the fragmentation regions, whereas strong violation of Feynman scaling is observed at midra- pidity. The KNO scaling in multiplicity distributions is violated at LHC also. The origin ofboth maintenance and violation of the scaling trends is traced to short range correlations of particles in the strings and interplay between the multi-string processes at ultra-relativistic energies. Long-range correlations between charged particles emitted in forward (F) and backward (B) hemispheres are studied also, good agreement with data at 546 GeV and 900 GeV is observed. The √dependence looks pretty linear and its slope increases with rising energy s [2]. The model is able to reproduce the effect of long-range nearside correlations, colloquially known as ridge [3]. In contrast to the F-B correlations this effect is attributed to hard Pomeron exchange and cannot be reproduced within the approach where only soft Pomerons are taken into account. The experimental femtoscopic radii dependences are well reproduced within Quark Gluon String Model. [1] J.Bleibel, L.Bravina, A.Kaidalov, E.Zabrodin, arXiv:1011.2703[hep-ph] [2] L.Bravina et al., Int. J. Mod. Phys. E (in press) [3] L.Bravina et al., (to be submitted) 109 / 478 √ Dimuon pairs from In-In collision at sNN = 17.3 GeV at SPS energies Jajati K. Nayak1 Bikash Sinha 1; Jan-e Alam 1; Sourav Sarkar 1 1 Variable Energy Cyclotron Centre The invariant mass√ and transverse momentum spectra of lepton pairs for In-In collision at sNN = 17.3 GeV have been studied. We find that the broadening of the ρ mesons spectral function due to its interaction with the thermal baryons causes substantial excess of dimuons at low mass region. Both the spectra agrees well with the experimental observations made by the NA60 collaborations. We argue that the non- monotonic variation of the slope parameter extracted from the transverse mass spectra for various invariant mass bins indicate the presence of two different phases during the evolution of the fireball. 80 / 479 165 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Nuclear suppression at large pT and xF: Direct photons from RHIC to LHC Jan Cepila1 Jan Nemchik 2 1 Faculty of Nuclear Sciences and Physical Engineering (FNSPE)-Czech Technical University in Prague 2 IEP SAS Kosice & FNSPE CTU in Prague We discuss a common feature of all known reactions on nuclear targets - a significant suppression at large Feynman xF and large transverse momenta pT of produced particles. The main emphasis is devoted to production of prompt photons since they are not expected to be accompanied by any final state interaction, either energy loss or absorption. Therefore, besides the Cronin enhancement at medium pT and small isotopic corrections at larger pT, one should not expect any nuclear effects. However, data from the PHENIX experiment demonstrate a significant large-pT suppression in cen- tral d+Au and Au+Au collisions that cannot be induced by coherence phenomena. We demonstrate that such an unexpected result is subject to the energy sharing problem in multiple initial state inter- actions. Using the colour dipole approach we describe first the large-pT production of direct photons in the RHIC kinematic region in agreement with available data. We study also a rise of nuclear effects with rapidity(xF) caused besides corrections for energy deficit by an increasing onset of coherence phenomena. In the LHC energy range we analyze relative manifestation of these effects presenting predictions for large-pT suppression at different rapidities. We analyze also a contribution of gluon shadowing as a leading twist shadowing correction modifying nuclear effects especially at small pT. 110 / 480 Measurement of neutral mesons at ALICE by means of one pho- ton detected in electromagnetic calorimeter and another from its conversion in central tracking system Alexander Borissov1 1 Wayne State University Measurement of neutral meson production from photon decays at ALICE experiment is performed by means of two electromagnetic calorimeters (EMCAL and PHOS) and/or conversion of photons in central tracking system. For two and more photon decaying mesons (pi^0, eta,omega) a possibility of combined calorimetry and conversion measurement is explored. It allows an inde- pendent cross check of data and systematic uncertainties given by two general approaches. pi^0 spectrum from proton-proton collisions at sqrt(s) = 7 TeV is presented from the analysis of 2010 data where one photon detected in EMCAL and another from its conversion. Spectrum is compared with separate measurement in each calorimeter. Perspectives of the applicability of combined calorimetry and conversion measurement are shown for 2011 data and PbPb collisions. 111 / 481 Low pT direct photon production in 200GeV d+Au collisions mea- sured by the PHENIX detector 166 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Yorito Yamaguchi1 1 University of Tokyo Direct photons in low pT region have been of great interest for a long time since thermal photons from Quark Gluon Plasma (QGP) are considered to contribute predominantly. Attempts to measure low pT direct photons using EMCals could not succeed since a finiteenergy resolution of the EMCal prevents us from separating direct photon signal from a large amount of background of hadron decay photons, particularly pi0. Recently, the PHENIX experiment demonstrated that direct photon yield can be obtained even in low pT region via the di-electron measurement since direct photon internal conversions make enhanced yield of di-electrons over the known√ hadron decay contributions. Comparing direct photon yields in sNN = 200 GeV p+p and Au+Au collisions, a significant excess over the binary scaled p+p result is seen in Au+Au for pT<3GeV/c. However, it should be confirmed that the observed excess of direct photons is not due tonuclear effects such as Cronin effect, nuclear anti-shadowing and so on, since nuclear effects are involvedin Au+Au collisions but not in p+p collisions. d+Au collision data can contribute to quantify nuclear effects on direct photon production. The latest results of low pT direct photons from d+Au data taken in the Year-2008 RHICRunwillbe shown. 140 / 482 Studies for an upgrade of the ALICE Inner Tracking System Cristina Terrevoli1 1 Universita degli Studi di Bari-Universita & INFN, Bari for ALICE ITS Collaboration Heavy quarks are fundamental probes to investigate the properties of the hot and dense QCD matter formed at the extreme energy densities reached in Pb-Pb collisions at LHC. The heavy quark pairs (cc_bar and bb_bar), which are produced in the very initial stage of the collision, come out from the interac- tion region as hadrons, possibly as a part of a jet, and carry out information about the properties of the traversed medium. Such information can be obtained from the study of the open charm and beauty hadrons in the final state and of the associated jet. Charm and beauty hadrons decay weaklywitha mean free path of the order of few hundred microns. Therefore, their identification relies on the possibility of resolving a decay vertex at distances of such order from the production one. The inner tracker of the ALICE experiment (ITS), made of six layers of silicon detectors, has been designed and built to this purpose and is providing the first results on the above mentioned item, though with some limitations. Adetector based on today’s frontier technologies would certainly offer new exciting possibilities within the physics scope described above. This contribution will present the studies on the upgrade of the ALICE ITS detector. Atthemoment, several possible scenarios for the new detector layout and technologies are being considered. With respect to the current ITS, the baseline idea for the upgraded tracker is to have a detection layer closer to the beam line 167 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / (which implies a beam pipe with smaller radius) and a larger number of layers instrumented with silicon pixels. The track position resolution at the primary vertex could be improved by a factor 2–3. Besides the natural improvement of the measurement capabilities on the channels already well mea- sured with the present ITS, the upgraded ITS will offer the possibility of exploring new physics items. Ex- amples are the heavy flavor baryons, the exclusive decay channels of B-mesons, the production mechanisms of hadrons containing more than one heavy quark. 141 / 483 Feasibility study of muon chamber for CBM experiment at FAIR Arun Prakash1 Anna Kiseleva 2; Bhartendu Kumar Singh 1; Evgeny Kryshen 3; Partha Pratim Bhaduri 4; Subhasis Chattopad- hyay 5 1 BHU,Varanasi,India 2 GSI, Darmstadt, Germany 3 SPbSPU, St Petersburg, Russia 4 Variable Energy Cyclotron Centre, Kolkata,India 5 Variable Energy Cyclotron Centre, Kolkata, India The compressed baryonic matter (CBM) experiment at the future FAIR accelerator center inDarm- stadt, Germany, aims at the investigation of baryonic matter at highest net baryon densities but moderate temperatures, by colliding heavy-ions at beam energies from 10 to 45 A GeV. The research program comprises the exploration of basic landmarks of the QCD phase diagram like transitions from hadronic to partonic phase, the region of first order de-confinement as well as chiral phase transition, and the critical end point. The proposed key observables include the measurement oflow mass vector mesons and charmonia, which can be detected via their decay into the di-lepton chan- nel. As the leptons leave the hot and dense fireball without further interactions, hence they provide almost unscathed information about the interior of the collision zone where they are being created. In this paper, we discuss the physics motivation, detector concepts, and the feasibility studies of the di-muon measurements for central Au + Au collisions, with a special reference to the detailed simulation activities performed by the CBM muon group. 71 / 484 D meson production cross sections in pp collisions at √s = 7 TeV, measured with the ALICE detector Grelli Alessandro1 1 Utrecht University Heavy quark production provides a powerful tool to test pQCD calculations in hadron collisions in the new energy regime of the LHC. Moreover the D meson pt-differential cross section in pp collisions provides the reference for the study of nuclear matter effects on charm quarks inPbPb collisions, via the nuclear modification factor. 168 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The ALICE experiment collected data in pp collisions at √s of 7 TeV and 2.76 TeV at theLHC.We present preliminary results on the pt-differential cross sections of D0, D*+, and D+ mesons, recon- structed using their hadronic decay channels. We show that already with a subsample of the 2010 data, thanks to excellent tracking system and particle identification capabilities of the ALICE exper- iment, the charmed hadron measurements in the mid-rapidity region can be extended down to pT~2 GeV/c, with good prospects to reach pT~1 GeV/c or below using the full sample. The current status of the Ds and Λc analysis, as well as the investigation of the charm content in jets, are discussed as well. 130 / 485 Lattice study of the second order transport coefficients Yasuhiro Kohno1 Chiho Nonaka 2; Masakiyo Kitazawa 1; Masayuki Asakawa 1 1 Osaka University 2 Nagoya University We attempt to constrain transport coefficients in second order viscous hydrodynamics by SU(3)lat- tice gauge simulation for the range of temperature 0.5 < T/T_c < 4. On the basis of the relaxation time approximation and Kubo formula, we relate a ratio of the shear viscosity to the relaxation time of the shear stress to fluctuations of off-diagonal components of energy-momentum tensor onthe lattice and evaluate them. 98 / 486 Study of pion-pion correlations at LHC and RHIC energies in pp collisions within the quark-gluon string model Mads Stormo Nilsson1 Evgeny Zabrodin 1; Larissa Bravina 1; Ludmila Malinina 2 1 Department of Physics, University of Oslo 2 Skobeltzyn Institute for Nuclear Physics, Moscow State University, Moscow, Russia The microscopic string model is employed for the description of femtoscopic characteristics of identical pions produced in pp collisions at energies of sqrt{s} = 200GeV (RHIC) and sqrt{s} = 900GeV (LHC). The strong decrease of the correlation radius with increasing transverse momentum of the pion pair is found in accord to STAR and ALICE experimental observations with flat baselines. In contrast to standard fit of thepion correlation function to single Gaussian, the double Gaussian fit reveals the contributions coming from resonances and from directly produced particles. The comparison of model results with the experimental data favors decrease of particle formation time with rising collision energy. The model is also employed to calculate the three-dimensional correlation functions, which gives good agreement with ALICE experimental data. 169 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Correlations and fluctuations / 487 A comprehensive study of the high-pt particle correlations in pp collisions at LHC/ALICE Yaxian Mao1 1 CCNU, Wuhan & LPSC, Grenoble Two-particle correlation with the high-pT triggers allows the study of the hard scattering phenomena like soft QCD radiation [1, 2], angular ordering [3] or jet frag- mentation in the low and intermediate pT region [4, 5] where full jet reconstruction is challenging. An analysis of the first ALICE pp data where charged particle, π0 and isolated photon are used as trigger particles will be presented. These measurements will serve as a reference for the same measurements in Pb-Pb collisions. A sensitivity of the associated particle momentum projection into the direction of the trigger particle, xE = −p Th± · p Ttrig / | p Ttrig |2, can be used to extract the average trigger particle momentum fraction and the jet imbalance function, whereas the γ-hadron correlations can be used to study the jet fragmentation function directly. The quest for the nuclear modification of the partonic properties in heavy ion collisions, using above mentioned quantities, will be also outlined. References [1] D. Boer and W. Vogelsang, Phys. Rev. D69, 094025 (2004), hep-ph/0312320. [2] R. Perez-Ramos, F. Arleo, and B. Machet, Phys. Rev. D78, 014019 (2008), 0712.2212. [3] Y. L. Dokshitzer, D. Diakonov, and S. Troian, Phys.Rept. 58, 269 (1980). [4] PHENIX, S. S. Adler et al., Phys. Rev. D74, 072002 (2006), hep-ex/0605039. [5] PHENIX Collaboration, A. Adare et al., Phys. Rev. D 82, 072001 (2010), arXiv:1006.1347. Heavy Flavors / 488 Charmonium and open-charm production in p-A collisions at the SPS Pietro Cortese1 1 Univ. del Piemonte Orientale, Dip.Scienze eTecnologie p-A collisions provide an essential reference for the study of J/psi suppression in heavy-ion data since they allow to evaluate cold nuclear matter effects. These include initial state effects like shadowing and parton energy loss and final state effects like J/psi breakup in the collisions with cold nuclear matter. To evaluate these, NA60 has measured J/psi production in p-A collisions at SPS energies with seven nuclear targets. In this analysis the J/psi cross section has been compared with open-charm pro- duction that is detected in the NA60 experiment through the simultaneous semi-muonic decay of D meson pairs. The comparison of the production of closed-charm with its natural reference al- lows to have some insight on how the interplay of the different processes gives rise to the observed (effective) J/psi suppression. 112 / 489 Measurement of Low Mass Electron-Positron Pairs with ALICE 170 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Christoph Baumann1 Markus Köhler 2 1 IKF, Goethe-Universität Frankfurt 2 EMMI, GSI The ALICE experiment at the CERN-LHC is dedicated to study the properties of theQuark-Gluon Plasma created in ultrarelativistic heavy-ion collisions. Low-mass electron-positron pairs are an excellent probe for all stages of the collision because they do not undergo strong final state in- teractions. With its unique tracking and particle identification capabilites extending to very low momenta, ALICE is excellently suited for these measurements. We will present first results on the production of low-mass electron-positron pairs at mid-rapidity in pp collisions at sqrt(s) = 7 TeV measured in ALICE and give an outlook on the low-mass program for Pb-Pb data. 490 Dissipative effect on the thermal photon spectra Sukanya Mitra1 Jane Alam 1; Sourav Sarkar 1; payal mohnaty 1 1 Variable Energy Cyclotron Centre The effects of the shear and the bulk viscosities on the transverse momentum distribution of thermal photons have been studied. The effects of viscosity have been taken into account both in the phase space distributions of the particles taking part in the production process as well as in the space time evolution. We argue that the thermal photons can be used as an efficient tool to estimate the transport coefficients of quark gluon plasma. 99 / 491 Femtoscopy of the proton-proton collisions at the LHC with pion- pion Bose-Einstein correlations in ALICE Adam Kisiel1 1 CERN We report on the results of identical pion femtoscopy of the pp collisions at the LHC with the Bose- Einstein correlations. We present the final analysis of the ALICE pp datasets at sqrt{s}= 0.9 TeVand 7 TeV and the preliminary results for sqrt{s}=2.76 TeV. Detailed pion femtoscopy studies in heavy-ion collisions have shown that emission region sizes (”HBT radii”) decrease with increasing pair momentum, which is under- stood as a manifestation of the collective behavior of matter. 3D radii were also found to universally scale with event multiplicity. In pp collisions at sqer{s} = 7 and 2.76 TeV one measures multiplicities 171 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / which are comparable with those registered in peripheral Au-Au and Cu-Cu collisions at RHIC, so direct comparisons and tests of scaling laws are now possible. We show the results of double-differential 3D pion Bose-Einstein femtoscopic analysis, as a function of multiplicity and pair momentum. The results for three collision energies are compared to results obtained in the heavy-ion collisions at similar multiplicity and pp collisions at lower energy. We identify the relevant scaling variables for the femtoscopic radii and discuss the similarities and differences to results from heavy-ions. The observed trends give insight into the soft particle production mechanism in pp collisions and suggest that a self-interacting collective system may be created in sufficiently high multiplicity events. Hadron thermodynamics and chemistry / 492 Resonance measurement in pp and PbPb collisions at LHC with the ALICE detector Alberto Pulvirenti1 – ALICE Collaboration 2 1 University / INFN Catania 2 – The study of resonances production in pp collisions contributes to the proper tuning of theQCD- inspired particle production models and to the better understanding of the underlying event, while in PbPb collisions resonances are good probes to estimate the collective properties of the fireball, and in particular its lifetime. Strange resonances can also contribute to the historical topic of strangeness production measure- ment. pT spectra have been measured for φ, K ∗ , Σ∗ and Ξ∗ resonances using data from pp collisions at 7 TeV in LHC, measured by the ALICE detector. Mesons were analyzed in a rapidity window of ±0.5 while baryons in a window of ±0.8. Results will be shown from comparisons with several MC models, which show in general an acceptable match, except for the Ξ∗ which appear to be underestimated. Moreover, first results from the analysis of φ resonance in Pb-Pb collisions at 2.76 ATeV willbe presented. Correlations and fluctuations / 493 K0sK0s correlations in 7 TeV proton+proton collisions from the ALICE experiment at the LHC Thomas Humanic1 1 Relativistic Heavy Ion Group, Department of Physics - Ohio State U. Identical neutral kaon pair correlations are measured in 7 TeV proton+proton collisions in the AL- ICE experiment. Neutral kaons are identified from their decay into π+π- pairs. K0sK0s correlation functions are formed in 4 multiplicity x 4 kT bins. The kaon source parameters Rinv and λ are ex- tracted from these correlation functions by fitting a Gaussian*PYTHIA model to them, the Gaussian 172 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / describing the Bose effect and PYTHIA accounting for the non-flat baseline found in proton+proton collisions. PYTHIA with the Perugia-0 tune is seen to describe well the dependence of the baseline shape of the K0sK0s correlation function on multiplicity-kT bin in the Qinv fitting range used of 0-1 GeV. Corrections to source parameters from the Lednicky model for the a0/f0 resonance are made and found to be large. K0sK0s correlations show a systematic increase in Rinv for increasing multi- plicity bin and decreasing Rinv for increasing kT bin as seen in ππ correlations in the proton+proton system, as well as seen in heavy-ion collisions. Also, K0sK0s correlations are observed to more or less “smoothly” extend this ππ Rinv behavior for the proton+proton system to ~3 times higher kT than the kT range measured in ππ correlations. Jets / 495 Jet Reconstruction and Jet Background Classification with the ALICE experiment in PbPb collisions at the LHC Christian Klein-Boesing1 1 IKP Muenster The quantification of the effect of parton energy loss, knownasjet quenching, is one of the major goals of jet and high pT measurements in heavy-ion collisions. Here, the aim of the reconstruction of jets, as compared to single particle measurements, is to provide a more direct access to the original parton properties and the modification of the fragmentation process in heavy-ion collisions. For a clear interpretation of the reconstructed jet properties and the measurement of the inclusive jet spectrum in heavy-ion collisions a detailed characterization of the background and its fluctuation is paramount. In particular collective effects within one event can enhance or deplete locally the levelof background and modify the jet energy scale. The ALICE detector with its excellent tracking capabilities isthe ideal tool to study jet reconstruction based on charged particles in the presence of correlated and uncorrelated background down to particle pT of 150 MeV/c. We will evaluate the evolution of background effects using different probes embedded into heavy-ion data and quantify their influence on the reconstructed jet spectrum. 72 / 496 √ Nuclear modification of charm quarks in Pb-Pb collisions at sNN =2.76 TeV at LHC Umme Jamil1 Dinesh Srivastava 2 1 SINP, Kolkata, India 2 VECC, Kolkata, India 173 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The charm quarks are expected to be produced atthe initial fusion of the ultrarelativistic heavy-ion collisions. Just after the production, they will propagate through the Quark Gluon Plasma (QGP) and will loose energy by colliding with quarks and gluons and radiating gluons. We calculate the nuclear modification factor RAA of charm quarks, produced from the√ initial fusion of partons in a nuclear collision, at sNN =2.76 TeV Pb-Pb collision at LHC at more forward rapidities . At the relativistic heavy-ion collisions, nuclear shadowing effect will also play an important role. In this study,we take in to account the effect of collisional and radiative energy loss of the charm quarks while passing through the QGP and also the gluon shadowing effect while calculating RAA. We have considered some of the important formalisms available in the literature for the calculation of medium-induced radiative and collisional energy loss. The shadowing effect is introduced by using EKS98 parameterization for structure functions. Hadron thermodynamics and chemistry / 497 K0s and Lambda production in PbPb collisions with the ALICE experiment Iouri BELIKOV1 1 IPHC, CNRS-IN2P3 We present the study of K0s and Lambda production performed with the ALICE experiment at the LHC in Pb-Pb collisions at sqrt(sNN)=2.76 TeV and pp collisions at sqrt(s)=0.9 and 7 TeV. The K0s and Lambda particles are reconstructed via their V0decay topology allowing their identification up to high transverse momenta. The corresponding baryon/meson ratios as a function of transverse momentum are extracted for Pb-Pb collisions in centrality bins and in the transverse momentum range from 1 to 10 GeV/c. They are also compared with the ones measured in pp events at the LHC energies of 0.9and7TeV as well as in Au-Au collisions at sqrt(sNN)=0.2 TeV from RHIC. 81 / 498 Unintegrated gluon distributions and k_t-factorization in forward hadron production in DIS and pA collisions Fabio Dominguez1 1 Columbia University Two different forms of unintegrated gluon distributions have been widely used in the literature to describe small-x phenomena. On one hand, the Weizsacker-Williams distribution explicitly counts 174 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / the number of gluons per state in a physical gauge but does not seem to be related to any known observables. On the other hand, the unintegrated gluon distribution defined as the Fourier transform of the color dipole cross section appears naturally in gluon production cross sections but has no partonic interpretation. We show that the Weizsacker-Williams distribution can be probed in a dijet production process in DIS whereas the Fourier transform of the color dipole appears in photon- jet production in pA collisions. More complicated processes involving two particle production can be described with an effective k_t-factorization where each specific process requires a newgluon distribution built from the two basic ones through convolution. Hadron thermodynamics and chemistry / 499 Multi-strange particle measurements in 7 TeV proton-proton and 2.76 TeV PbPb collisions with the ALICE experiment at the LHC D.D. Chinellato1 1 Instituto de Fisica Gleb Wataghin (IFGW) - Universidade Estadual de Campinas The production of charged multi-strange particles is studied with the ALICE experiment attheCERN − − LHC. Measurements of the central rapidity yields of Ξ and Ω baryons, as well as their√ antiparticles, are presented as a function of transverse momentum (pT ) for inelastic pp collisions at s = 7 T eV and compared to existing measurements performed at the same and/or at lower energies. The results are also compared to predictions from PHOJET and several tunes of the PYTHIA event generators. We find that data significantly exceed the production rates from those models, everywhere except potentially for high pT , where hard QCD processes dominate.√ Finally, we present the status of the multi-strange particle production studies in Pb-Pb at s = 2.76 T eV performed as a function of collision centrality. Future facilities and experiment upgrades / 500 The next decade of physics with PHENIX Anne Sickles1 1 Brookhaven The first decade of RHIC physics and the first heavy ion running at the LHC have produced awealth of data and discoveries. It is timely to now evaluate what has been learned and ask what compelling new questions have been raised. In this talk, several key unanswered questions about the properties of the strongly coupled quark gluon plasma and the distribution of partons inside nucleons and nuclei will be discussed along with how they can be addressed experimentally. The PHENIX Collaboration has developed a plan for upgrading the experiment in order to address these new questions. The current status of these plans will be presented. Global and collective dynamics / 501 √Elliptic flow at high transverse momentum in PbPb collisions at sNN = 2.76~TeV with the ALICE experiment 175 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Alexandru Florin Dobrin1 1 Wayne State University As a consequence of the energy loss of highly energetic parton propagating through a dense medium, jet quenching is an important probe of QGP created in high energy heavy-ion collisions. Jet quench- ing leads to the suppression of particle production at high transverse momenta. An observable that can be used to better constrain the mechanism responsible for the parton energy loss is the elliptic azimuthal event anisotropy, v2, which provides differential information on the particle yield and jet quenching relative to the reaction plane. We report on measurements of the elliptic√ event anisotropy for unidentified charged particles with pT up to 20~GeV/c in Pb-Pb collisions at sNN = 2.76~TeV recorded by the ALICE experiment at the LHC. Additionally, we report on measurement of v2 for identified particles with pT < 10~GeV/c; pions and protons are identified using the ionization energy loss in the TPC. The results arecom- pared to the measurements at lower energy reported by RHIC experiments but also to theoretical predictions. 64 / 502 Pt spectra of hadrons identified with the ALICE Inner Tracking System Leonardo Milano1 1 Universita degli Studi di Torino-Universita e INFN The Inner Tracking System is the ALICE detector closest to the beam axis. It is composed ofsix layers of silicon detectors: two innermost layers of Silicon Pixel Detectors (SPD), two intermediate layers of Silicon Drift Detectors (SDD) and two outermost layers of Silicon Strip Detectors (SSD). The ITS can be used as a standalone tracker in order to recover tracks that are not reconstructed by the Time Projection Chamber (TPC) and to reconstruct low momentum particles with pt down to 100~MeV/c. Particle identification in the ITS is performed by measuring the energy loss signalin the SDD and SSD layers. The ITS allows to extend the charged particle identification capability in the ALICE central rapidity region at low pt: it is possible to separate π/K in the range 100 MeV/c < pt < 500 MeV/c and K/p in the range 200 MeV/c < pt < 800 MeV/c. The identification of hadron in the ITS will be discussed in detail, different methods used to extract the pt spectra of π, K and p will also be described. Heavy flavors / 503 Measurement of J/psi production at forward rapidity in pp colli- sions at sqrt(s)= 2.76 and 7 TeV with ALICE Roberta Arnaldi1 1 INFN Torino The ALICE experiment has studied J/psi production at forward rapidity from pT=0, throughits dimuon decay channel, in proton-proton and Pb-Pb collisions at the LHC. Results obtained in proton-proton collisions at sqrt(s)=7 TeV will be discussed. The integrated and 176 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / differential (in pT and rapidity) inclusive production cross sections will be presented and compared to results from other LHC experiments. First results on the J/psi integrated and differential cross sections in proton-proton collisions at sqrt(s)=2.76 TeV will also be discussed. These measurements, at the same centre-of-mass energy as for Pb-Pb collisions, provide a crucial reference for the study of nuclear matter effects on J/psi production. Theory developments / 504 Electrical conductivity and thermal dilepton rate from quenched lattice QCD. Olaf Kaczmarek1 1 University of Bielefeld We report on a continuum extrapolation of the vector current correlation function for light valence quarks in the deconfined phase of quenched QCD. This is achieved by performing a systematic anal- ysis of the influence of cut-off effects on light quark meson correlators at T=1.5 Tc usingclover improved Wilson fermions [1]. In addition new results at 1.2 and 3.0 Tc will be presented. The first two, non-vanishing thermal moments of the vector meson spectral function are determined and compared with those for free, massless quarks. We discuss resulting constraints on the electrical conductivity and the thermal dilepton rate in a quark gluon plasma. [1] H.-T. Ding et al. Phys.Rev.D83(2011)034504 Hadron thermodynamics and chemistry / 505 Measurement√ of π/K/p spectra√ with ALICE in proton-proton col- lisions at s = 900 GeV and s = 7 TeV Marek Chojnacki1 1 UU/NIKHEF The ALICE experiment features several particle identification systems, which allow us to measure spectra in a broad range of transverse momentum pt from 100 MeV/c up to a few GeV/c. √ New results on identified charged particle pt spectra measured in proton-proton collisions at s = 7 TeV will be presented. They will be compared to results obtained at 900 GeV and lower energies, theoretical modelsand commonly used event generators. √ The large statistics collected in collisions at s = 7TeV allows us to measure the spectra and yields as a function of the event multiplicity, reaching a dN/dη comparable to nuclear collisions at lower energy. The status and perspective of such measurement will also be presented. Electromagnetic probes / 506 177 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Photons at RHIC and at the LHC: the role of viscosity and of event-by-event fluctuations Charles Gale1 Bjoern Schenke 2; Clint Young 1; Jean-Francois Paquet 1; Maxime Dion 1; Sangyong Jeon 1 1 McGill University 2 Brookhaven National Laboratory We investigate the yield and the azimuthal anisotropy of produced photons in heavy-ion collisions at RHIC and at LHC energies. We study the photons produced from a variety of sources, including those from primordial nucleon-nucleon collisions, from thermal partons, from fragmenting QCD jets, from jets interacting with thermal partons, and from thermal hadrons. We study the interplay of those sources, in an evolving 3D simulation of the colliding system that involves hydrodynamics and hard jets. We study ideal and viscous fluids, and we evaluate the effect of fluctuating initial conditions, and of using different hadronic equations of state. Under all of the above conditions, we quantify the ability of real photons to act as penetrating probes of the hot and dense strongly interacting medium. Correlations and fluctuations / 507 Anisotropic flow of charged particles at 2.76 TeV measured with the ALICE detector Ante Bilandzic1 1 NIKHEF Ante Bilandzic for the ALICE collaboration Measurements of anisotropic flow provided evidence for the creation of strongly interacting matter which appears to behave as an almost ideal fluid. Anisotropic flow signals the presence of multiple interactions and is very sensitive to the initial spatial anisotropy of the overlap region in non-central heavy-ion collisions. In this talk we report measurements of elliptic v2, triangular v3, quadrangular v4 and pentagonal v5 flow. These measurements have been performed with two- and multi-particle correlation techniques. We will show how these measurements can be understood from the initial spatial anisotropy and its fluctuations. These observations provide a possible explanation forthe away-side features often attributed to Mach cone effects. Electromagnetic probes / 508 Measurements of low mass dielectrons in Au+Au collisions with the HBD upgrade of the PHENIX detector Mihael Makek1 1 Weizmann Institute of Science Dileptons are valuable probes in the investigation of the hot and dense matter formed in heavy ion collisions, since they interact only electromagnetically andthus 178 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / their path from the interaction region to the detectors is almost undisturbed. They can provide information about the matter properties in the early stages of the collisions where deconfinement and chiral symmetry restoration are expected to take place. However, the measurements of dileptons in heavy ion collisions are challenging due to the overwhelming yield of pi0 Dalitz decays and photon conversions, which produce a large combinatorial background especially in the low invariant mass region (m_ee<1 GeV/c^2). The PHENIX spectrometer has been upgraded with a Hadron Blind Detector (HBD) with thepur- pose of reducing the combinatorial background from the dielectron mass spectrum. The HBD is a windowless Cherenkov detector, operating with pure CF_4, using triple GEM elements with a CsI photocathode and pad readout. The HBD reduces the combinatorial background by exploiting the small opening angle of the pi0 Dalitz and conversion pairs. It was successfully operated during Run 9 and Run 10 at RHIC in the measurements of e+e- pairs in p+p collisions at sqrt(s)=200 GeV and in Au+Au collisions at sqrt(s_NN) = 200 GeV, 62 GeV and 39 GeV. In this talk a full account of the HBD and present results of the dielectron analysis in Au+Au collisions at sqrt(s_NN)=200 GeV with improved signal to background ratio, will be presented. Heavy flavor / 509 Heavy-flavor production cross section in the semi-electronic chan- nel at mid-rapidity in pp collisions at sqrt(s)=7 TeV with ALICE Silvia Masciocchi1 1 GSI Darmstadt Heavy quarks (charm and beauty) are among the most important probes that allow to test perturba- tive QCD descriptions of hard processes in hadronic interactions, as well as to study the hot matter produced in high energy nucleus-nucleus collisions. Precision measurements of heavy flavour pro- duction in proton-proton collisions provide the necessary reference for the interpretation of their behaviour in the deconfined state of strongly-interacting matter (Quark-Gluon Plasma). Both colli- sion systems can be extensively studied with ALICE at LHC. The production of heavy quarks can be measured via the detection of their semileptonic decays.We present the measurement of the inclusive electron spectrum at mid-rapidity, in proton-proton colli- sions and sqrt(s)=7 TeV, based on the excellent particle identification capabilities of ALICE. The statistical subtraction of a cocktail that accounts for photonic electrons and other background sources, built on the base of ALICE measured meson spectra, provides a measurement of the pro- duction cross section of electrons from heavy-flavour hadron decays. The further subtraction ofthe charm component, obtained from the D meson cross section measured by ALICE in the same rapid- ity range, as well as an analysis of impact parameter distributions relative to the interaction vertex, allow to determine the electron spectrum from pure beauty decays. The results will be presented, compared to theoretical predictions, and discussed in the perspective of obtaining a reference for the studies of heavy quark energy loss in the Quark-Gluon Plasma. Energy scan / 510 Collision energy dependence√ of the flow and spectra results in Au+Au collisions at sNN = 7.7-200 GeV from PHENIX Xiaoyang Gong1 179 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Stony Brook University A central goal in experimental nuclear physics is to map out the QCD phase diagram, and to measure precisely the properties of the different phases. In order to achieve this goal, RHIC has embarked on an energy scan program involving gold nuclei at various energies.√ The data collected by the PHENIX experiment for this program consists of data sets obtained at sNN = 200, 62, 39 and 7.7 GeV. The analysis of these data, have yielded a wealth of new soft physics results which are usedincon- cert to probe reaction dynamics and to constrain the transport coefficients of hot QCD matter. One particularly effective probe that is emphasized in this talk is√ the anisotropy of particle production, characterized by flow coefficients v2 and v4. For Au+Au collisions at sNN = 200 GeV, measure- ments indicate a hydrodynamic flow of hot QCD matter at the partonic level with a small butfinite value of the viscosity to entropy density ratio. However, at sufficiently low collision energy (thus lower energy density and temperature), we expect this picture to break down. Therefore measure- ment of the collision energy dependence of v2 and v4 could provide new insights to the current understanding of the nature of interactions in hot QCD matter. We present new energy scan measurements of flow coefficients for both unidentified and identified particles, as well as several other soft physics observables such as identified hadron spectra andHBT correlations. The implications of these results will also be discussed. 142 / 511 New experiments for study of in-medium vector mesons at J-PARC Kyoichiro Ozawa1 1 KEK The origin of the hadron mass has been drawing strong interests in nuclear and particle physics. Especially in QCD, mass of hadrons is composed of a sum of the effective mass of valence quarks, known as constituent quark mass, and their interaction term. According to theoretical models, the effective mass of valence quarks is determined by chiral property of QCD vacuum. This mechanism is understood as a consequence of the dynamical breaking of chiral symmetry. In hot and/or dense matter, this broken symmetry will be restored either partially or completely and, hence, properties of hadrons, such as mass, decay modes and life time, can be modified. Therefore, we can study the origin of hadron mass and chiral properties of QCD medium by measuring in-medium properties of mesons. Especially, mass spectra of vector mesons are directly connected to anti-quark quark condensates, which is an order parameter of chiral symmetry. Thus, it is important to measure mass spectra of vector mesons in QCD medium, such as Quark Gluon Plasma or nuclear matter. Even at nuclear matter density, relatively large mass modification is predicted and several experi- mental efforts using cold nucleus targets are already performed. Among these activities, KEK-E325 reported significant mass modifications for rho and phi mesons and CLAS G7 experiment report only mass broadening for rho meson. Obtained results are different and physics behind these exper- imental results are not clearly understood. To understand the physics, clear and high statistics experimental data are essential. We are prepar- ing new experiments to obtain such data at J-PARC. One experiment is an upgrade of E325 and aims to collect 100 times larger statistics in phi going to e+e- decays. Another experiment focus on exclu- sive measurements of stopped omega meson in nucleus. In this poster, we will report on details of two experiments and results of detector R&D. Energy scan / 512 Energy dependence of energy loss in Au+Au collisions at PHENIX 180 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Norbert Novitzky1 1 Department of Physics-University of Jyvaskyla The suppression of inclusive pion production by up to a factor of 5, which was first observedinAu + Au at √sNN= 130 GeV/c (e.g. [1]) and later in Au + Au at √sNN= 200 GeV/c [2, 3], is one of the most significant manifestations of the opaque QGP produced in heavy ion collisions. Theabsence of this suppression in d + Au collisions at the same energy indicates the final state nature of the suppression. It is natural to ask where the onset of such massive suppression is in terms of the energy density of the medium which is dictated by the collision energy, centrality and the mass of colliding nuclei. The PHENIX collaboration has studied collisions of lighter nuclei (Cu +Cu)at different beam energies in 2005 [4]. While a significant suppression is observed both at√sNN=200 and 62.4 GeV, at √sNN = 22.4 GeV a moderate enhancement is found. In 2010 RHIC scanned lower energies, and PHENIX collected substantial data sets in Au + Au collisions at √sNN = 39 and 62 GeV. The goal was to identify better the conditions for the onset of the π0 suppression. This talkpresents results from the systematic study of c.m. energy and the system size dependencies of π0 yield and the nuclear modification factor. References [1] K. Adcox et al., Phys.Rev.Lett. 88, 022301 (2002). [2] S. S. Adler et al., Phys.Rev.Lett. 96, 202301 (2006). [3] A. Adare et al., Phys.Rev.Lett. 101, 232301 (2008). [4] A. Adare et al., Phys.Rev.Lett. 101, 162301 (2008). 32 / 513 Pseudorapidity density of charged√ particles and its centrality de- pendence in Pb-Pb collisions at sNN = 2.76 TeV Hans Hjersing Dalsgaard1 1 Niels Bohr Institute, University of Copenhagen Hans Hjersing Dalsgaard\footnote{\texttt{[email protected]}}\\ (for the ALICE collaboration) We present the first measurements√ of the pseudorapidity (η) distribution in a wide range for different centralities in Pb-Pb collisions at sNN = 2.76 TeV. Using the SPD and FMD detectors of ALICE we can cover a wide region in η: −3.4 < η < 5. The distributions yield the total number of produced charged particles in Pb+Pb collisions at the LHC energy. The dependence of dNch/dη on the number of participant nucleons or on the number of binary collisions is sensitive to models describing the mechanism underlying par- ticle production (eg. gluon saturation models). In this contribution ALICE data will be compared to current models and an analysis of longitudinal scaling will be performed. 100 / 514 System-size dependence of particle ratio fluctuations in Pb+Pb collisions at 158 AGeV Dmytro Kresan1 1 GSI, Germany 181 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / According to the QCD calculations on the lattice, the dynamical fluctuations of, for example, strangeness to entropy ratio could be enhanced in the co-existance region of the first order phase transition from hadronic to partonic degrees of freedom and in the vicinity of the critical point. The energy dependence of the K/pi ratio fluctuations measured bythe NA49 experiment in central Pb+Pb collisions shows increase towards lower energies, which is not reproduced by the UrQMD model. One of the possible explanations is the scaling of the dynamical fluctuations with average kaon multiplicity. In order to study this hypothesis one would like to fix the acceptance of the detector and measure the event-by-event fluctuations as a function of centrality at fixed beam energy. In this poster, the centrality dependence of event-by-event fluctuations of K/pi, p/pi and K/p ratios measured by the NA49 experiment in Pb+Pb collisions at 158A GeV will be presented. For all consid- ered ratios, dynamical fluctuations are found to increase in absolute value by 7 - 10% with decreasing centrality. Comparing the centrality and energy dependence of the particle ratio fluctuations, they are found to scale with the particle number dominating the fluctuation measure. I.e. in particular the event-by-event K/pi fluctuations are found to scale with the number of kaons. For p/pi fluctuations the observed scaling supports the interpretation that the measured dynamical fluctuations are a rem- nant of nucleon resonance feeddown. Detailed investigations have been performed to systematically study the influence of detector acceptance and particle identification. 101 / 515 LHC results on femtoscopic pi+pi correlations from the UrQMD transport approach Gunnar Gräf1 Marcus Bleicher 1 1 Frankfurt Institute for Advanced Studies We use the non-equilibrium transport approach Ultra-relativistic Quantum Molecular Dynamics (UrQMD) [1] to compute the dynamics of heavy ion collisions up to LHC energies. From this model we obtain directly the full phasespace distribution of all particles at the kinetic freeze out. By using the quantum reweighting technique on the freeze out distribution we extract the two-particle corre- lation function in three-dimensions. Using a gaussian parametrization we get the Hanbury-Brown Twiss (HBT) radii from these correlation functions which can be interpreted in terms of the space- time extension [2] of the particle-emitting source. A comparison of correlation functions andHBT radii with LHC data will be shown. [1] S. A. Bass et al., Prog. Part. Nucl. Phys. 41 (1998) 225. [2] S. Chapman et al., Phys. Rev. Lett. 74 (1995) 4400 Hadron thermodynamics and chemistry / 516 Validity of the hadronic freeze-out curve Francesco Becattini1; Marcus Bleicher2; Michael Mitrovski3; Reinhard Stock4; Thorsten Kollegger2; Tim Schuster4 1 Universita de Firenze and INFN Sezione di Firenze 2 rankfurt Institute for Advanced Studies (FIAS) 3 Brookhaven National Laboratory, Physics Department 182 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 4 Institut fuer Kernphysik - Johann-Wolfgang-Goethe Univ. In nucleus-nucleus collisions we distinguish early hadro-chemical freeze-out, fixing hadronic con- centrations, and final kinetic freeze-out to spectral and flow features, occuring at the endofthe hadronic “cascade” phase. This view has been adopted in all recent analysis of hadron production rates, which are well described in the grand canonical statistical equilibrium model. The derived freeze-out systematics in the (T,mu(B)) plane occurs in all present sketches of the QCD matter phase diagram. It merges with the lattice QCD parton-hadron coexistence line at small mu(B). The preservation of the equilibrium pattern of hadronic yields (established in the close vicinityof hadronization) throughout the final hadronic expansion phase still remains to be explained, andsub- stantiated. In order to systematically assess the effect of the hadronic cascade stage we employ the hybrid ver- sion of the UrQMD transport model. In it, a high density hydrodynamic evolution stage is matched, via the Cooper-Frye formalism, to the final hadron/resonance expansion evolution. Matching occurs at a fixed critical energy density. These calculations are carried out at the energies covered bythe SPS Pb+Pb program, 6.3 < squrr(s) < 17.3 GeV. At each energy we determine, both, the hadron yield distribution arising directly after hadronization, and the eventual distribution resulting from the UrQMD hadron/resonance expansion “afterburner” stage. The latter turns out to preserve the bulk production channels but to systematically reduce the antibaryon yields, with exception of the Omega/Antiomega. We revisit the data in view of these predictions. Finally we analyze all these yield distributions with the grand canonical statistical model, determin- ing the freeze-out curve before/after the cascade afterburner. A significant shift of this curve occurs (to lower T, higher mu(B)) which, however, is essentially absent if the antibaryon yields are excluded, but with exception of the Omega/antiOmega yields. The cascade stage thus appears to distort the initially imprinted equilibrium distributions, but only selectively so: an effect that must be avoided in the data analysis. Thus one recovers the T, mu(B) established before the cascade stage. 518 Derivation of Causal Relativistic Hydrodynamic Equations and Novel Moment Method Kyosuke Tsumura1 Teiji Kunihiro 2 1 Fuji Film Co. 2 Kyoto University This is an extention of our previous work[1,2] to the derivation of the causal relativistic hydro- dynamic equations in generic local rest frames for a viscous fluid from the relativistic Boltzmann equation. Our derivation is based on the renormalization group method[3] as a powerful reduction theory of the dynamics. We have identified some drawbacks in our previous derivation of the casusal equations[4]. Our improved equation is a natural extension of the first-order equation derived by the present authors.[1] The relaxation times derived in our microscopic theory have forms which can be nicely interpreted in terms of correlation functions. Our equation in any local rest frame including the particle frame has a definite stable thermal equilibrium state and is completely free from the instability problem. Our equation in the energy-frame is found quite different from the one by Denicol et al [5] whichis derived on the basis of a moment method; but our equation can be well approximated by it when the Rits approximatin is valid for a rarefied gas. On the basis of our derivation, wepro- pose the correct moment method for the derivation of causal hydrodynamic equations without ad-hoc ansatz. 183 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / References [1] K. Tsumura, T. Kunihiro and K. Ohnishi, Phys. Lett. B 646 (2007) 134. [2] K.Tsumura and T. Kunihiro, Phys. Lett. B 668 (2008) 425. [3] L.Y.Chen, N.Goldenfeld and Y.Oono, Phys. Rev. Lett.73 (1994) 1311; T.~Kunihiro, Prog. Theor. Phys.94 (1995) 503 [Erratum-ibid.95 (1996) 835]. [4] K.Tsumura and T.Kunihiro, Phys. Lett. B 690 (2010) 255. [5] G.S.Denicol, T.Koide and D.H.Rischke, Phys. Rev. Lett. 105 (2010) 162501 Heavy Flavors / 519 Recent PHENIX results on open heavy flavor J. Matthew Durham1 1 Stony Brook University Throughout the history of the RHIC physics program, questions concerning the dynamics ofheavy quarks have generated much experimental and theoretical investigation. A major focus of the PHENIX experiment is the measurement of these quarks through their semi-leptonic decay chan- nels at mid and forward rapidity. Heavy quark measurements in p+p collisions give information on the production of heavy flavor, without complications from medium effects. New measurements in d+Au indicate significant and surprising cold nuclear matter effects on these quarks at midrapidity, and provide a newbaseline for interpretation of the observed suppression in Au+Au collisions. To complement the measured heavy quark spectra, correlations between heavy quark decay products give information on jet mod- ification in nuclear collisions, while correlations between heavy quarks and hadrons produced inthe same event can shed light on interactions with the medium. When considered all together, these measurements present a detailed study of nuclear matter across a wide range of system size andtem- perature. This talk will present new PHENIX measurements of non-photonic electron spectra and their centrality dependence in d+Au, and discuss their implications on the current understanding of parton energy loss in the nuclear medium. 33 / 520 Triangular flow and nonflow by 2-, 4-, and 6-particle cumulants from STAR Li Yi1 1 Purdue University Triangular flow (v3) can arise from event-by-event fluctuations. Its connection to fluctuations inthe initial state collision geometry may reveal hydrodynamic information of the collision system. Theoretical studies suggest its sensitivity to hydrodynamic evolution may even be stronger than el- liptic flow (v2). √ We present v3 measurement by the 2-, 4-, and 6-particle cumulant method at sNN = 200 GeV in Au+Au collisions by STAR. We compare our v3 results to v2, also from the multiparticle cumulant method. The 2-particle cumulant result contains nonflow contribution. We assess the nonflow effect bysep- arating charges as well as applying a pseudo-rapidity gap. The 4- and 6-particle v3 results are strongly affected (perhaps dominated) by v3 fluctuations. Assuming Gaussian flow fluctuation, we further attempt to distinguish flow, flow fluctuation, and nonflow. 184 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Global and collective dynamics / 521 Midrapidity charged particle directed flow in PbPb collisions at sqrt{s_{NN}} = 2.76 TeV measured with ALICE at the LHC Ilya Selyuzhenkov1 1 EMMI/GSI Azimuthal anisotropic flow is a key observable indicating collectivity among particles produced in non-central heavy ion collisions. Directed flow is characterized by the first harmonic coefficient in the Fourier decomposition of the particle azimuthal distribution with respect to the collision reaction plane. It develops at a very early stage of the collision and thus is sensitive to the properties and the equation of state of the hot and dense matter produced in ion-ion collisions. We report on results for midrapidity (|eta|<0.8) charged particle directed flow measured in lead-lead collisions at 2.76 TeV collision energy recorded with the ALICE detector at the LHC. The orienta- tion of the collision reaction plane is reconstructed with the help of the spectator neutrons detected by the pair of ALICE Zero Degree Calorimeter detectors. Directed flow results obtained with dif- ferent measurement techniques are presented as a function of collision centrality, charged particle transverse momentum, and pseudo-rapidity. 35 / 522 Photonuclear interactions in ultra-peripheral Pb+Pb collisions at the LHC Joakim Nystrand1; Oeystein Djuvsland1 1 Department of Physics & Technology-University of Bergen [email protected], [email protected] The strong electromagnetic fields present in ultra-peripheral Pb+Pb collisions at the CERNLHC accelerator lead to large cross sections for particle production in photonuclear interactions[1]. It will be shown that photonuclear processes may constitute a significant background to peripheral and semi-central hadronic nuclear collisions. The cross sections for photonuclear interactions induced by photons from the electromagnetic fields of the nuclei have been calculated. The photon spectrum has been evaluated in impact parame- ter space. Thereby one can easily exclude collisions were the nuclei interact hadronically (b<2R). For modelling the particle production, the DPMJET[2] Monte Carlo event generator has been used. Calculations have been done for photon energies from 6 GeV to 100 TeV in the rest frame of the target nucleus, which is the energy range contributing to particle production around mid-rapidity. The multiplicity, rapidity, and transverse momentum distributions of produced particles will bepre- sented. Two cases of photonuclear processes have been considered, single and double excitation. In the former case, one of the nuclei emits a photon which interacts with the other nucleus, whereas in the latter case both nuclei emit photons which interact with the other nucleus. The crosssection for single excitation is much larger than that of double excitation. However, the topology of the double excitation events, where the rapidity distruction is more symmetrical, is simililar to that of hadronic interactions. Both processes may thus contribute significantly to the background of hadronic interactions, depending on the experimental event selection. The photon-nucleon energies that can be reached in ultra-peripheral collisions at the LHC arehigher than for any earlier gamma+A or gamma+p collisions. In addition to being a background for hadronic 185 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / interactions, such events have a physics interest in themselves. Photoproduction of heavy quarks (e.g. cc-bar through gamma-gluon fusion) and jets have large cross sections and probe the nuclear parton distribution functions. [1] O. Djuvsland, J. Nystrand, arXiv:1011.4908, to be published in Phys. Rev. C. [2] S. Roesler, R. Engel, J. Ranft, Phys. Rev. D 57 (1998) 2889. Correlations and fluctuations / 523 Event-by-event mean pT fluctuations in pp and PbPb collisions measured by the ALICE experiment at the LHC Stefan Heckel1 1 Johann-Wolfgang-Goethe Univ. Non-statistical event-by-event fluctuations of the mean transverse momentum of charged particles in pp and Pb–Pb collisions are studied using the ALICE experiment at the LHC. The analysis is per- | | formed at η <√0.8 and 0.15 < pT < 2~GeV/c. Multiplicity√ dependent results are obtained for pp collisions at s~=~0.9, 2.76 and 7~TeV. Pb–Pb collisions at sNN ~=~2.76~TeV are analysed in intervals of multiplicity and centrality, the latter in bins of 5\%. Little collision energy dependence is observed in pp collisions. The data indicate acommonscal- ing behaviour with event multiplicity from pp to semi-central Pb–Pb collisions. In central Pb–Pb collisions, the results deviate from this trend, exhibiting a significant reduction of the fluctuation strength. The results are compared to measurements in Au–Au collisions at lower collision energies and to Monte Carlo simulations with PYTHIA and HIJING. 36 / 524 Shear viscosity in a partonic cascade Christian Wesp1; Felix Reining1 1 Goethe Universität Frankfurt [email protected], [email protected] We simulate an ultra-relativistic gluon gas in a partonic cascade using the Boltzmann Approach for Multi Parton Scattering (BAMPS) with pQCD-based interactions. Furthermore elastic 2<->2 andin- elastic 2<->3 processes with constant cross sections are implemented. The hydrodynamic transport parameter shear viscosity is extracted via two different approaches: first from a relativistic station- ary velocity gradient and in a second method from equilibrium fluctuations using a Green-Kubo relation. Both methods are compared to an analytic relation and are used to investigate the alpha_s dependece of the shear viscosity to entropy ratio in a partonic gas at T>T_c. 20 / 525 My suppression, your flow, his Cronin - our insight Gabor David1 186 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Brookhaven National Laboratory Despite rapidly improving experimental precision, theory sophistication and the large variety of available data a coherent description of the properties of the hot, dense medium produced in relativistic heavy ion collisions remain so far elusive. Using SPS, RHIC and LHC heavy ion nuclear modification and flow data we will look atthe evolution (system size and collision energy) as well as the interplay of initial state effects, dynamic and static properties of the medium. We will look at the data in some unorthodox ways in order to clarify what we can and what we can not learn from these type of measurements. Global and collective dynamics / 526 PHENIX measurements√ of higher-order flow harmonics in Au+Au collisions at sNN = 200 GeV: implications for Initial-eccentricity models and the specific viscosity of the Quark Gluon Plasma Roy Lacey1 1 Stony Brook University The higher-order flow harmonics vn can provide constraints crucial for precision√ extraction of the specific shear viscosity eta/s, of the plasma (QGP) produced in full energy( sNN = 200 GeV) Au+Au collisions at RHIC. It can also provide reliable estimates of the flow correlations which con- tribute to the underlying event for jet-driven two-particle azimuthal angle correlation studies; the latter is important to the development of a quantitative understanding of the opacity oftheQGP. Thus, significant recent attention has been given to theoretical studies of vn (odd and even) and the associated initial [fluctuating] eccentricities which drive vn. In recent experiments, the PHENIX Collaboration has made detailed differential measurements of vn (odd and even) relative to the participant event planes Ψn, as well as measurements of the correlations between different Ψn planes. The results from these measurements will be presented. Comparisons to LHC dataand hydrodynamical calculations will be shown as appropriate. We will also discuss the detailed im- plications of these measurements for (i) improved precision for separating the flow and jet-driven contributions to ∆Φ correlation functions, (ii) distinguishing between the two leading eccentricity models, and (iii) a more constrained estimate of η/s. 37 / 527 Charged-particle transverse momentum spectra in proton-proton collisions at √s = 0.9 TeV, 2.76 TeV and 7 TeV measured with AL- ICE at the LHC Michael Linus Knichel1 1 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm- stadt, Germany Inclusive charged-particle transverse momentum distributions have been measured in proton-proton collisions at √s = 0.9, 2.76 and 7 TeV with the ALICE detector at the LHC. The measurements in the 187 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / central pseudorapidity region |η| < 0.8 cover a transverse momentum range of 0.15 < p_T < 50 GeV/c. The evolution of the transverse momentum spectra as a function of the collision energy andthe charged particle multiplicity is presented. The spectra are compared to measurements from other experiments, to predictions from next-to-leading order QCD calculations and to simulations with the Monte Carlo event generators PYTHIA and PHOJET. The results can be used to tune theoretical models and serve as the baseline for the comparison with particle production in heavy-ion colli- sions. 156 / 529 Electromagnetic superconductivity of vacuum in strong magnetic field and heavy ion collisions Maxim Chernodub1 1 University of Tours, France Recently, we have suggested that the vacuum in a strong external magnetic field experiences a spon- taneous phase transition to an electromagnetically superconducting state. The unexpected supercon- ductivity of, basically, empty space is induced by emergence of quark-antiquark vector condensates with quantum numbers of electrically charged rho mesons. The ultra-periferal heavy-ion collisions generate high magnetic fields which may be used as an experimental tool to probe the existence of the electromagnetic superconductivity of the cold vacuum. In our talk we discuss potentially observable signatures of vacuum instability towards the exotic superconducting state. 73 / 530 Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decays at Mid-Rapidity in Pb-Pb Collisions at sqrt(s_NN)=2.76 TeV with ALICE Yvonne Pachmayer1 1 Ruprecht-Karls-Universitaet Heidelberg-Unknown-Unknown In high-energy nucleus-nucleus collisions, heavy flavour quarks, i. e. charm and bottom, are pro- duced on a very short time scale in the initial hard scattering processes and thus they experience the whole history of the collision. Therefore, they are valuable probes to address the features ofthein- teraction of hard partons with the hot and dense state of matter, that is expected to be formed inthe collision. In particular, they allow us to study parton energy loss and its quark mass dependence. Heavy flavour production can be measured in several channels by the ALICE experiment atthe LHC. We present the transverse momentum spectrum of electrons from heavy flavour decays at mid-rapidity in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV, as obtained by subtracting from the inclu- sive electron sample a data-tuned cocktail of the non-heavy-flavour background contributions. By comparison with a pp reference scaled to the same centre-of-mass energy, we determine the nuclear modification factor of the pt distribution of electrons from heavy flavour decays. 74 / 531 Charmonium dynamics in the UrQMD transport model 188 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Thomas Lang1 Marcus Bleicher 1 1 Frankfurt Institute for Advanced Studies We study charmonium physics in heavy-ion collisions within the framework of the non-equilibrium transport model UrQMD. Using this model we compute different heavy quark observables like the nuclear modification factor RAA, high pT suppression and the elliptic flow v2. The UrQMD approach includes explicit interactions of the charmed particles with the surrounding medium. Different cross sections for charmonium dissociation and charmonium recombination by D-Mesons are tested at SPS, RHIC and LHC energies. We show that these results are in good agreement with measurements at the different collision energies. Energy scan / 532 Net-baryon-, net-proton-, and net-charged particle kurtosis in heavy- ion collisions within a relativistic transport approach Marcus Bleicher1; Marlene Nahrgang2; Michael Mitrovski3; Reinhard Stock4; Tim Schuster4 1 Frankfurt Institute for Advanced Studies(FIAS) 2 Goethe University Frankfurt and Frankfurt Institute for Advanced Studies (FIAS) 3 Physics Dept.,BNL, Brookhaven 4 Frankfurt Institute for Advanced Studies(FIAS) and Institut fuer Kernphysik, University of Frankfurt We explore the potential of net-baryon, net-proton and net-charge kurtosis measurements to investigate the properties of hot and dense matter created in relativistic heavy-ion collisions. Contrary to calculations in a grand canonical ensemble we explicitly take into account exact electric and baryon charge conservation on an event-by-event basis. This drastically limits the width of baryon fluctuations. A simple model to account for this is to assume Poisson distributions with a sharp cut-off at the tails. We present baseline predictions of the energy dependence of the net-baryon, net-proton and net-charge kurtosis for central (b ≤ 2.75~fm) Pb+Pb/Au+Au collisions √from Elab = 2A~GeV to sNN = 200~GeV from the UrQMD model. While the net-charge kurtosis is compatible with values around zero, the net-baryon number decreases to large negative values√ with decreasing beam energy. The net-proton kurtosis becomes only slightly negative forlow sNN . 38 / 533 Photoproduction of Vector Mesons in Ultra-Peripheral Pb-Pb Col- lisions at the LHC Joakim Nystrand1 189 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Department of Physics and Technology The strong electromagnetic fields surrounding the Pb-ions accelerated at the CERN LargeHadron Collider (LHC) allow two-photon and photonuclear interactions to be studied in a kinematic regime so far unexplored. In ultra-peripheral collisions, with impact parameters larger than the sum of the nuclear radii, hadronic interactions are strongly suppressed but the cross sections for electro- magnetic or photon-induced interactions are large. The interactions can be purely electromagnetic (two-photon interaction) or a photon from the field of one of the nuclei may interact with theother nucleus (photonuclear interaction). Exclusive interactions, where both nuclei remain in their ground state, are dominated by coherent photonuclear vector meson production and two-photon production of di-lepton pairs. During the heavy-ion run at the LHC in 2010 where Pb-Pb collisions at an energy of sqrt(s_NN) = 2.76 TeV were studied, the ALICE Experiment had triggers enabled for exclusive particle production in ultra-peripheral collisions. These included trigger information from the Time-of-Flight, Silicon Pixel, and V0 Detectors. A trigger for ultra-peripheral collisions was also enabled in the muon arm. The integrated luminosity for the ultra-peripheral triggers corresponds to about 3.6 microb^- 1. Results on photoproduction of rho0 and J/Psi from the data collected with these triggers will be presented. Coherent rho0 production at mid-rapidity at the LHC corresponds to a photon-nucleon center of mass energy of 45 GeV, roughly a factor of 4 higher than has been studied before. Photoproduction of J/Psi is of particular interest, since it has been proposed as a sensitive probe of the nuclear gluon distribution down to x = 10^-3. The results can be compared with models with different mechanisms for the nuclear shadowing. 75 / 534 Measurement of J/ψ → e+e− Production in Pb-Pb Collisions at √s = 2.76 TeV with ALICE at the LHC Julian Book1 Jens Wiechula 2 1 Institut fuer Kernphysik - Frankfurt 2 Eberhard-Karls-Universitaet Tuebingen The investigation of the properties of strongly interacting matter under extreme conditions isthe aim of the LHC heavy ion program. Quarkonia states such as the J/ψ will provide insights into the earliest and hottest stages of heavy ion collisons where the formation of a Quark-Gluon Plasma (QGP) is expected. Measuring these bound states of heavy quarks via their dileptonic decay modes is one of the goals of the ALICE experiment. We will present the current status of the challenging J/ψ analysis in the electronic decay channel at √s = 2.76 TeV in Pb-Pb collisions. Invariant mass spectra as well as first estimates of J/ψ yields are obtained using the tracking and particle identification capabilities of the Inner Tracking System (ITS), the Time Projection Chamber (TPC) and the Time of Flight (TOF). Heavy flavors / 535 J/psi production at forward rapidity in PbPb collisions at sqrt(s_NN) = 2.76 TeV, measured with the ALICE detector 190 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Philippe Pillot1 1 SUBATECH, Nantes Heavy quarkonium states are expected to provide essential information on the properties of the high-density strongly-interacting system formed in the early stages of high-energy heavy-ion col- lisions. Such probes are especially promising at LHC energies, where heavy quarks are copiously produced. ALICE is the experiment at the LHC mainly dedicated to the study of nucleus-nucleus collisions. At forward rapidity (2.5 < y < 4), the production of heavy quarkonium states is measured down to pT = 0 via their mu+mu- decay channels in the Forward Muon Spectrometer. After a short description of the apparatus, the analysis of the inclusive J/psi production in the first Pb-Pb data collected in the fall 2010 at a center of mass energy of sqrt(s_NN) = 2.76 TeV will be presented. Preliminary results on the nuclear modification factor (R_AA) and the central to peripheral nuclear modification factor (R_CP) will then be discussed. Electromagnetic probes / 536 √ Low mass dimuon production in proton-nucleus collisions at s = 27.5~GeV with the NA60 experiment Antonio Uras1 1 INFN Cagliari, IPNL Lyon The study of the production of low mass vector and pseudoscalar mesons in proton-nucleus colli- sions represents a natural baseline for the heavy-ion observations, allowing to provide a reference in an environment of cold nuclear matter. In-medium modifications of the vector meson spectral func- tions were actually predicted to occur also in cold nuclear matter, though the experimental evidence at the moment is controversial. Proton-nucleus collisions also give access to the study of strangeness production as a function of the size of the nucleus, providing a robust ground for strangeness en- hancement in nuclear collisions. Besides that, the study of the nuclear dependence of particle prop- erties in proton-nucleus collisions, as the transverse momentum spectra and the production cross sections, is an effective tool to understand the dynamics of soft hadron interactions. The NA60 experiment√ has collected an unprecedented statistics of 180000 low mass muon pairsin proton-nucleus data at s = 27.5~GeV exposing to the beam six target materials: Be, Cu, In, W, Pb and~U. The very good statistical accuracy and dimuon mass resolution allowed us toperforma precision measurement of the ρ line shape related the T parameter of the Boltzmann factor, which was measured for the first time in p-A collisions. The ρ − ω interference was also investigated and preliminary results are reported. No evidence of in-medium effects is found. In addition, the electromagnetic transition form factors of the η and ω mesons were also measured, with a significant precision improvement with respect to the previous measurements. The ω results, compared to the latest theoretical developments, still show the presence of an anomaly which is not described by theory. For the ω and ϕ mesons, thanks to the good acceptance coverage, the transverse momentum spectra were measured down to zero pt. Finally, the nuclear dependence of the production cross sections was investigated in terms of the α power law σpA ∝ A , and the α parameter was studied as a function of pt. 65 / 537 191 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Study of central production in pp-collisions at √s=7 TeV with the ALICE experiment Xianguo Lu1 1 Physikalisches Institut-Ruprecht-Karls-Universitaet Heidelberg The ALICE experiment consists of a central barrel covering the pseudo-rapidity range −0.9 < η < 0.9 and of additional detectors which can be used to define pseudo-rapidity gaps on both sides (\mbox{−3.7 < η < −0.9} and \mbox{0.9 < η < 5.1}). The low pT threshold of the central barrel gives ALICE a unique opportunity to study the low mass sector of central diffractive production at the LHC. √ ALICE has collected proton-proton collision data at s = 7 TeV from March to November 2010. I will report on the analysis of events with a double-gap signature based on this data sample of about 8 4×10 minimum bias events. An enhancement of f0(980) and f2(1270) is seen in these double-gap events as compared to no-gap events. Hadron thermodynamics and chemistry / 538 Production of neutral pions and eta-mesons in pp collisions mea- sured with ALICE Klaus Reygers1 1 University of Heidelberg 0 The inclusive production of π and η mesons is measured at mid-rapidity√ in pp collisions over a wide transverse momentum (pT ) range with the ALICE experiment at s=900GeV, 2.76~TeV and 7~TeV. The mesons are measured via two different techniques: with the calorimeters (PHOS andEMCAL) and via photon conversions reconstructed in the Central Tracking System. 0 A systematic√ comparison to next-to-leading order pQCD (NLO) calculations for π and η mesons as well as the s-dependence of the π0 production is presented. Furthermore, the η to π0 ratio as well as the corresponding NLO calculations are discussed. The presented data serves as a baseline both for the decay photon background for direct photon measurements as well as for the background of electrons in open heavy flavor measurements. It will then be used to calculate the nuclear modification factor, RAA, in heavy-ion collisions with ALICE. 76 / 539 Measurement of the Multiplicity Dependence of J/ψ → e+e− Pro- duction in √s = 7 TeV pp Collisions with ALICE at the LHC Frederick Kramer1 1 IKF, Goethe-Universität Frankfurt 192 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / ALICE is the dedicated heavy-ion physics experiment at the Large Hadron Collider (LHC). It is de- signed to provide excellent capabilities to study the Quark-Gluon Plasma (QGP), the deconfined state of strongly-interacting matter, in the highest energy density regime opened up by theLHC. Quarkonia, bound states of heavy (charm or bottom) quarks such as the J/ψ, are crucial probesof the QGP. Before drawing conclusions on QGP-induced phenomena all non-QGP effects influencing quarkonia yields have to be understood. ALICE has measured the charged particle multiplicity distribution at √s = 7 TeV pp collisions [1]. A good fraction of events feature multiplicities that are of the same order as in central heavy-ion collisions at SPS energies. Thus, final-state effects present in heavy-ion collisions, such asapos- sible interaction with comovers [2], might be unveiled at LHC energies studying the multiplicity dependence of J/ψ production in pp collisions. We will present first results of the multiplicity dependence of J/ψ production in √s = 7 TeV ppcolli- sions. The analysis is based on the reconstruction of the channel J/ψ→e+e− using the central barrel detectors of ALICE. References [1] K. Aamodt et al., “Charged-particle multiplicity measurement in proton-proton collisions at √s = 7 TeV with ALICE at LHC”, EPJ C 68 (2010) 345. [2] A. Capella et al., “J/ψ suppression at √s = 200 GeV in the comovers interaction model”, EPJ C 42 (2005) 419. Global and collective dynamics / 540 √Charge dependent azimuthal correlations in PbPb collisions at sNN = 2.76~TeV Panos Christakoglou1 1 NIKHEF - Utrecht University Separation of charges along the extreme magnetic field created in non-central relativistic heavy-ion collisions is predicted to be a signature of local parity violation in strong interactions. We report on results for charge dependent√ two particle azimuthal correlations with respect to the reaction plane for Pb-Pb collisions at sNN = 2.76~TeV recorded in 2010 with ALICE at the LHC. The results are compared with measurements at RHIC energies and against currently available model predictions for LHC. Systematic studies of possible background effects including comparison with conventional (parity-even) correlations simulated with Monte-Carlo event generators of heavy-ion collisions will be also presented. Hadron thermodynamics and chemistry / 541 Vector meson production in pp collisions at sqrt(s)=7 TeV, mea- sured with the ALICE detector Alessandro De Falco1 1 Univ. + INFN Cagliari Low mass meson (ρ0, ω, ϕ) production provides key information on the hot and dense state of strongly interacting matter produced in high-energy heavy ion collisions. Among them, strangeness 193 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / enhancement can be accessed through the measurement of ϕ meson production, while the measure- ment of the ρ spectral function can be used to reveal in-medium modifications of hadron properties close to the QCD phase boundary. Vector meson production in pp collisions provides a reference for these studies. Moreover, it is interesting by itself, since it can be used to tune particle production models at the unexplored LHC energy range. The ALICE experiment at the LHC can access vector mesons produced at forward rapidity through their decays in muon pairs, and at central rapidity in the di-electron decay channel. We present√ transverse momentum spectra of ϕ and ρ+ω mesons at forward rapidity in pp collisions at s = 7~TeV, as well as the ϕ absolute production cross section. We will also discuss the first signals√ and the analysis prospects for vector meson studies at forward rapidity in Pb-Pb collisions at sNN = 2.76~TeV. 77 / 543 Constraining Cold Nuclear Matter Effects on J/ψ production in Au +Au Collisions Darren McGlinchey1 Anthony Frawley 1 1 Florida State University Recent results from PHENIX on J/ψ production in d+Au collisions have shown that J/ψ’s are significantly suppressed at forward rapidity. This has interesting implications for J/ψ suppression in Au+Au collisions, and may provide an answer to the J/ψ puzzle. We try to constrain these cold nuclear matter (CNM) effects by fitting the EPS09 parametrization plus a break-up cross section to the PHENIX data in each rapidity range. In contrast to previous work, a stronger than linear dependence of initial-state shadowing on the nuclear thickness is employed to better fit the d+Au data. We extrapolate our results to predict the CNM effects on J/ψ production in Au+Au collisions and compare with the PHENIX results. We find that some J/ψ suppression remains in central collisions after factoring out the CNM effects and that the forward and midrapidity data are now in agreement within uncertainties. Correlations and fluctuations / 544 Measurements of Bose-Einstein correlations at LHC with CMS Collaboration CMS1 1 UCLouvain [email protected], [email protected] Bose–Einstein correlations between identical particles are measured in samples of proton-proton collisions at 0.9 and 7 TeV centre-of-mass energies, recorded by the CMS experiment at the LHC. The signal is observed in the form of an enhancement of number of pairs of same-sign charged particles with small relative momentum. The dependence of this enhancement on kinematic and topological features of the event is studied. 78 / 545 194 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / MEASUREMENT OF SINGLE-MUON AND J/\psi PRODUCTION AT FORWARD RAPIDITY AS A FUNCTION OF THE COLLISION MULTIPLICITY IN PP COLLISIONS AT \sqrt{s} = 7 TeV WITH AL- ICE Matthieu Lenhardt1 1 Laboratoire de physique subatomique et des technologies associee Recently, it has been argued that high-multiplicity pp collisions could lead to the formation of high energy density matter as in heavy ions collisions [1]. Indeed, the charged particle multiplicity reached in pp collisions at the LHC [2] is similar to the one measured in semi-peripheral Cu-Cu collisions at \sqrt{s_{NN}} = 200 GeV [3]. We will present the dependence on charged particle multiplicity of the single-muon and J/\psi \rightar- row \mu^{+}\mu{-} yields in pp collisions at \sqrt{s} = 7 TeV. The number of reconstructed tracklets (\eta<1.6) in the silicon pixel detector are exploited to measure the charged particle density at mid- rapidity. Single-muons (p_{T}>4 GeV/c) from heavy flavoured hadron decays and inclusive J/\psi (p_{T}>0) yields have been measured with the muon spectrometer (2.5<\eta<4.0). J/\psi yields at multiplicities five times the average pp multiplicity will be presented. [1] K. Werner et al. arXiv:1010.0400v1, and K. Werner et al., Phys. Rev. Lett. 106, 122004 (2011) [2] ALICE Collaboration, EPJC: Vol. 68 (2010) 345 [3] PHOBOS Collaboration, Phys. Rev. C 83, 024913 (2011) Jets / 546 Suppression of neutral pion production at large transverse mo- mentum√ measured with the ALICE experiment in PbPb collisions at sNN =2.76 TeV Gustavo Conesa Balbastre1 1 LPSC - Grenoble The ALICE experiment at the LHC has measured√ the transverse momentum spectra of neutral mesons via the two photon decay in pp and Pb-Pb collisions at sNN =2.76 TeV over a wide transverse mo- mentum range with different subsystems: with the electromagnetic calorimeters PHOS and EMCAL and via conversions of the photons in the inner material of the experiment to e+e–pairs reconstructed with the Central Tracking System. In this talk, the production of neutral pions in pp and Pb-Pb collisions is compared in terms of the so called nuclear modification factor, RAA, for different centrality selections of the Pb-Pb data sample. 66 / 547 Production of nuclei and anti-nuclei in pp and Pb-Pb collisions with ALICE at the LHC Natasha Sharma1 195 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Department of Physics, Panjab University, Chandigarh, India We present the first results on the production of nuclei and anti-nuclei such as (anti)deuterons, (anti)tritons, (anti)3He and (anti)4He in pp collisions at √s = 7 TeV and Pb-Pb collisions at √sNN = 2.76 TeV. These particles are identified using their energy loss (dE/dx) information in theTime Projection Chamber of the ALICE experiment. The Inner Tracking System gives a precise deter- mination of the event vertex, by which primary and secondary particles are separated. The high statistics of over 350 M events for pp and 16 M events for Pb-Pb collisions give a significant number of light nuclei and anti-nuclei (Pb-Pb Collisions: anti-deuterons ~ 30,000 and anti-alpha ~ 4). The study of these particles will help to understand their production mechanism. Various particle ratios obtained from these collisions and their comparison with different predictions from statistical and coalescence models will also be discussed. Jets / 548 Charged particle production at large transverse momentum in PbPb collisions at sqrt(s)=2.76 TeV measured with ALICE at the LHC. Jacek Otwinowski1 1 Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darm- stadt, Germany The observed suppression of high-pT particle production in heavy-ion collisions is generally at- tributed to energy loss of partons as they propagate through the hot and dense QCD medium. Inclu- sive transverse momentum spectra of primary charged particles in Pb-Pb collisions at sqrt(s)=2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented in intervals of collision centrality. The charged particle spectra are compared to those measured in pp collisions at the same collision energy, scaled by the number of underlying nucleon-nucleon collisions. This comparison is expressed in terms of the nuclear modification factor R_AA. The results indicate only weak medium effects in peripheral collisions, while there is clear evidence for strong medium ef- fects in central collisions. In this talk we will present the results of an analysis of the full Pb-Pb statistics obtained in the Nov. 2010 run. With these data the transverse momentum range covered is increased to 50 GeV/c as compared to previous studies of R_AA by ALICE. The evolution of R_AA with collision centrality and transverse momentum will be discussed. 102 / 549 Transverse√ sphericity in minimum bias proton-proton collisions at s = 0.9 and 7 TeV with ALICE at the LHC Antonio Ortiz Velasquez1 1 Universidad Nac. Autonoma de Mexico (UNAM) A study of the√ linearized sphericity in minimum bias proton-proton collisions at s = 0.9 and 7 TeV with the ALICE detector at the LHC is presented. The observable was measured in the plane perpendicular to the beam direction and using primary charged tracks in |η| ≤ 0.8. The average sphericity as a function of multiplicity is reported for events with different hardness (soft” andhard”) defined by a cut on the transverse momentum of the leading particle.In 196 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / addition to those studies the average transverse momentum versus multiplicity was measured for different event classes. Data are compared with PYTHIA6 (tunes: ATLAS-CSC and PERUGIA-0), PYTHIA8 and PHOJET. The behavior of the linearized sphericity and of the mean pT with multiplicity indicates that the current event generators tend to “build up” multiplicity by generating more jets while on the contrary the data indicate that at high multiplicity the events tend to be more isotropic and the mean pT smaller. 79 / 550 Measurement of J/psi polarization at forward rapidity in pp col- lisions at sqrt(s)=7 TeV with the ALICE detector Livio Bianchi1 1 Universita degli Studi di Torino-Universita & INFN, Torino-Unkno The ALICE experiment at the LHC measures quarkonium and open heavy flavour production down to low transverse momentum (pt=0, for quarkonium) at forward rapidity in the muon channel. In this scope, the quarkonia and heavy flavour physics program in pp collisions aims to define a proper normalization for nuclear collision studies and to address prominent unresolved issues, such as the determination of the quarkonium production mechanism. Polarization is considered as one of the most promising observables to discriminate among all the theoretical models for quarkonia production. First results on the polarization of J/psi mesons produced at forward rapidity in sqrt(s)=7TeV pp collisions will be presented. 67 / 551 Topological reconstruction of strange hadrons in Pb-Pb collisions with the ALICE experiment Marian Putis1 1 Pavol Jozef Safarik University, Kosice, Slovakia The studies of strange particle production provide information about the dynamics of thesystem which was created in Pb-Pb or pp collisions at LHC energies. Reconstruction of strange particles based on their decay topology allow us to extract yields over a large transverse momentum range (from ~ 0.6 GeV/c up to ~ 8 GeV/c). The ALICE experiment provides high statistics data from proton- proton and Pb-Pb collisions for this study. The analysis is focusing on strange particles K0s and Lambdas created in Pb-Pb collisions at sqrt(sNN)=2.76 TeV. The main principles of geometrical re- construction and signal extraction are presented. The efficiency is obtained from Monte -Carlo simulations and used to correct the raw yields. Finally, our latest results related to Lambda and K0s analysis are presented. 39 / 552 Inclusive photon production at forward rapidities for pp colli- sions at √s = 0.9 TeV and 7 TeV in ALICE at the LHC 197 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Sudipan De1 1 Variable Energy Cyclotron Centre (VECC)-Department of Atomic Ene We report the first measurement of the multiplicity and pseudorapidity distributions of photons in the pseudorapidity region of 2.3 < η < 3.9 in proton-proton collisions at center of mass energies of 0.9 TeV and 7 TeV at the LHC. The photon measurement is dominated by neutral pion decays andthus complimentary to those of the charged particles. Multiplicity distributions at both energies follow double Negative Binomial Distributions (NBD). We observe that the average photon multiplicity in- creases logarithmically with the beam energy. Photon multiplicity and pseudorapidity distributions for inelastic and non-single diffractive events are compared with results from event generators (Pho- jet, Pythia). Phojet is close to the data at 0.9 TeV, but both models under-predict the observed data at 7 TeV. Limiting fragmentation behavior is studied by combining with measurements from other experiments and then compared to the models. 80 / 553 Photoproduction of J/Psi in Ultra-Peripheral Pb+Pb collisions at sqrt(s_NN)=2.76 TeV in ALICE Daniele De Gruttola1 1 University and INFN of Salerno - CERN When two relativistic nuclei collide with impact parameter larger than twice their radius (b>2R_A), they may interact in several ways: nuclear excitation with neutron emission, two-photon exchange, coherent production of vector mesons with pomeron or gluon exchange. These events are usually referred as Ultra Peripheral Collisions (UPC). A relevant process is the production of vector mesons containing heavy flavours: this is a powerful tool to study the gluon distribution function inthe nuclei, up to x as low as 10^-4. In this presentation we show the performance of the ALICE detector in the search for J/psi produced in UPC events during the first LHC Pb-Pb run atsqrt(s_NN)=2.76 TeV. The total cross section for this process is a small fraction of the total Pb-Pb cross section, therefore dedicated triggers have been used to tag these events both in the barrel and in the forward muon arm. The details of the data analysis, the cut optimization and the first J/psi candidate eventsare shown. Global and collective dynamics / 555 Diffraction dissociation of protons in proton-proton collisions at \sqrt{s} = 0.9 TeV, 2.76 TeV and 7 TeV with ALICE at the LHC Martin Poghosyan1 1 Universita & INFN, Torino (for the ALICE Collaboration) The relative rates of single‐ and double‐ diffractive processes were measured with the ALICEde- tector by studying properties of gaps in the pseudorapidity distribution of particles produced in proton‐proton collisions at \sqrt{s} = 0.9 TeV, 2.76 TeV and 7 TeV. ALICE triggering efficiencies were 198 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / determined for various classes of events, using a detector simulation validated with data on inclu- sive particle production. Cross‐sections were determined using van der Meer scans to measure beam properties. 81 / 556 Cold Nuclear Modification of J/psi Production in d+A and A+A Collisions Matthew Wysocki1 1 University of Colorado Boulder The production of heavy quarkonia in high-energy nuclear collisions is a problem that is stillpoorly understood, even without the presence of the quark-gluon plasma. The most common method of calculation is with nuclear-modified parton distribution functions and a break-up cross section for the (pre-J/psi) c-cbar pair passing through the nucleus. Calculations of this nature will be presented (as detailed in arXiv:1011.4534) with different assumptions about the geometric dependence ofthe nuclear modifications, and the results will be compared to the latest PHENIX d+Au experimental data. It will be demonstrated that no combination of nPDFs and sigma_breakup, regardless of the nPDF parameter set and the assumed geometric dependence, can simultaneously describe the entire rapidity and centrality dependence of J/psi modifications in d+Au collisions at sqrt(s_NN) = 200 GeV. We will also extend the calculations to include a simple model of initial-state parton energy loss, with the same result. We will then compare the results of these calculations with others using coherent J/psi production and gluon saturation at low x. Finally, we will project these calculations to Au+Au collisions at sqrt(s_NN) = 200 GeV, and compare to the latest experimental data for that case. 79 / 557 Measurement of inclusive neutral pion yields in in p+p and Pb+Pb collisions at √sNN=2.76 TeV with the ALICE EMCal Ermes Braidot1 1 Lawrence Berkeley National Lab. (LBNL) 0 We present the√ measurement of inclusive differential π yields in p+p and centrality-selected Pb+Pb collisions at sNN = 2.76TeV, using the large-acceptance ALICE Electromagnetic Calorimeter (EMCal). The recently completed EMCal enhances ALICE capabilities for the study of jets, neutral mesons, electrons, and direct photons. The EMCal acceptance (110 degrees in azimuth, |η|0.7) and high granularity enable the reconstruction of neutral mesons over a wide transverse momentum range, employing invariant mass, shower-shape, and conversion techniques. We present first mea- 0 0 surement of π RAA for both√ peripheral and central Pb+Pb collisions, normalized by the π yield measured in p+p collisions at sNN = 2.76TeV. 157 / 558 Nonequilibrium effects at the phase transition in chiral fluid dy- namics including dissipation and noise 199 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Marlene Nahrgang1 Marcus Bleicher 2; Stefan Leupold 3 1 Goethe-University Frankfurt and Frankfurt Institute for Advanced Studies (FIAS) 2 Frankfurt Institute for Advanced Studies (FIAS) 3 Uppsala University We present a dynamic study of nonequilibrium fluctuations and correlations at the chiral phase tran- sition starting from the linear sigma model with constituent quarks. Within the formalism of the two-particle irreducible (2PI) effective action the nonequilibrium dy- namics of the sigma field coupled to the fluid dynamic expansion of quarks is obtained consistently. We derive the Langevin equation for the sigma field with the explicit damping coefficient andthe noise terms, which are similar to those we obtain from the influence functional method. The 2PI effective action in addition contains information about the local equilibrium properties of thequark fluid like the energy density and the pressure, which are needed for the equation ofstate.Wego beyond existing studies of Langevin dynamics at the chiral phase transition by putting special em- phasis on the properties and the evolution of the heat bath. The damping in the dynamics of the sigma field leads to energy dissipation from the field to the fluid. In the exact formalism ofthe2PI effective action a conserved energy-momentum tensor can be constructed. Investigating the coupled dynamics of the sigma field and the expansion of the quark fluid wepresent results on the intensity of sigma fluctuations and the correlations at the critical point and thefirst order phase transition observing strong nonequilibrium fluctuations and correlations. Hadron thermodynamics and chemistry / 559 High-pT suppression of Lambda and K0s in PbPb collisions at sqrt(sNN) = 2.76 TeV with ALICE Simone Schuchmann1 1 Institut fuer Kernphysik-Johann-Wolfgang-Goethe Univ. Significant suppression of unidentified charged particles at large transverse momentum hasbeen observed in central Pb-Pb collisions at the LHC. Measurements of identified particles will provide more detailed information on the suppression mechanism. The production of Lambda and K0s at mid-rapidity in pp and Pb-Pb at sqrt(sNN) = 2.76 TeV is studied with the ALICE detector at the LHC. Lambda and K0s are measured by recon- structing their weak decays into charged hadrons, employing the tracking capabilites of the ALICE central barrel. The analysis of Lambda and K0s production in Pb-Pb is performed in intervals ofthe collision centrality and compared to results from pp at the same collision energy. We discuss the centrality dependence with particular emphasis on strange particle suppression at high pT. Correlations and fluctuations / 560 Triggered di-hadron correlations in PbPb collisions from the AL- ICE experiment Andrew Adare1 1 Yale University 200 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Angular correlations between unidentified hadron trigger and (t),(a) associated particles are measured by the ALICE experiment for 0.5 < pt < 15 GeV/c, where (t) (a) pt > pt . The modification of conditional yields in central Pb–Pb collisions is measured with respect to p–p (IAA) and with respect to peripheral events (ICP ). Significant suppression is observed on the side opposing the trigger, while an enhancement is measured on the near side. The latter result is a notable departure from RHIC measurements. In addition, the shape of the pair azimuthal distribution is examined in a variety of centrality categories for pairs in |η| < 0.8 where |η(t) − η(a)| > 0.8. A set of two-particle Fourier components Vn∆ ≡ ⟨cos(n∆ϕ)⟩ are computed directly from the long-range azimuthal correlation functions. A series including V1∆ to V5∆ describes the data. For each n, a fit is applied over all pT bins (t) (a) simultaneously to test the collectivity hypothesis Vn∆ ≃ vn vn . This factorization hypothesis is satisfied at low pT but not at higher pT . The divergence between the data and the global fit provides a new measure of the onset of nonflow dominance in long-range correlations due to the away side jet. The first five single-particle vn coefficients are presented as new results from the global fit, and are compared to vn values measured by more established methods. 40 / 561 Elliptic Flow from the Parton-Hadron-String-Dynamics Elena Bratkovskaya1; Vadim Voronyuk2; Viacheslav Toneev2; Volodymyr Konchakovski3; Wolfgang Cassing3 1 Institute for Theoretical Physics, Frankfurt University 2 Dubna, JINR 3 Institute for Theoretical Physics, Giessen University We present a systematic study of correlations in pseudorapidity and azimuthal angle for charged high transverse momentum hadrons in heavy-ion collisions at the top RHIC energy within the Parton- Hadron-String-Dynamics (PHSD) transport approach. The study shows that a significant part (60%) of the high-pT hadron attenuation seen experimentally can be attributed to inelastic interactions of ‘leading’ pre-hadrons with the dense hadronic environment. The presence of partonic phase leads to larger suppression of ‘far-side’ correlations which agrees with available data. We find also a fair description of the elliptic flow of charged hadrons as a function of the energy of the reaction,its centrality and the transverse momentum pT within PHSD approach. Furthermore, an approximate quark-number scaling of the elliptic flow v2 of hadrons is observed in the PHSD results, too. Thuswe conclude that partonic phase plays significant role for the both: high-pT correlations and collective flow. 103 / 562 Multiplicity Dependent Di-Hadron Correlations Measured with ALICE at the LHC Eva Sicking1 201 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Universität Münster / CERN A Large Ion Collider Experiment (ALICE) is the experiment at the Large Hadron Collider (LHC) optimized for heavy-ion collisions. However, ALICE is also studying pp collisions which not only provides important reference measurements but is also part of a stand-alone pp physics program. In particular, high multiplicity pp collisions are an interesting field of study of particle production mechanisms. Here we present the results of a di-hadron angular correlation analysis which has the aim to mea- sure the number of multi-parton interactions and mini-jet fragmentation properties as a function of multiplicity. We discuss the problems encountered with standard correlation measurements at high multiplicities and present solutions to cope with these. Results are compared between dif- ferent center of mass energies. Also, comparisons between different Monte Carlo generators are discussed. Jets / 563 Anomalous baryon production and its interplay with jet energy loss at RHIC and LHC energies Peter Levai1 Attila Pasztor 2; Daniel Berenyi 2; Vladimir V. Skokov 3 1 KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 2 Eötvös University, Budapest, Hungary 3 GSI, Darmstadt, Germany The study of the nuclear suppression factor of charged hadrons and neutral pions in AuAu collisions at RHIC energies indicated the possible appearance of an anomaly at higher pT-s: although protons are expected to be produced from gluons, but jet energy loss is less effective for them comparing to pion suppression. Fragmentation function and jet energy loss based explanation can not reproduce this phenomena, which opens a discussion on anomalous baryon production at high-pt. We investi- gated the appearance of non-perturbative hadron production channels connected to the formation of strong non-abelian fields, and their strength at RHIC and LHC energies. We performed calculations with time dependent strong fields and studied the quark-pair and diquark-pair production at high-pT to produce leading quarks and diquarks to be hadronized. The numerical results are presented and discussed. 21 / 564 A data driven√ validation of the Pythia jet cross section in pp col- lisions at s = 2.76 TeV Hermes Leon Vargas1 1 IKF Goethe-Universität Frankfurt am Main [email protected] √ Studies of the inclusive jet production in Pb-Pb collisions at s = 2.76 TeV and its possible modi- fication by the hot and dense medium, require a comparison of the measured jet spectrum tothat from pp collisions at the same center of mass energy. The goal of our study is to validate a reference 202 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / spectrum obtained via Pythia simulations, using jet cross section measurements at the Tevatron and the LHC. We present comparisons of data driven extrapolations and interpolations with the predictions from Pythia6, using the tune Perugia-0. 104 / 565 Charged KK femtoscopy correlations from 7 TeV pp collisions measured by ALICE collaboration. Ludmila Malinina1 ALICE for the ALICE Collaboration 2 1 Joint Inst. for Nuclear Research (JINR)-Unknown-Unknown 2 CERN Charged KK femtoscopy correlations from 7 TeV pp collisions measured by ALICE collaboration. L. Malinina (SINP MSU-JINR) for the ALICE collaboration We report on the results of charged kaon femtoscopy analysis of the 7 TeV pp collisions at the LHC in the ALICE experiment. KK correlation functions are constructed in 3 multiplicity and 4 kt bins. The KK source parameters are extracted by fitting the correlation functions with Gaussian, describing the source, multiplied by a polynomial background function with free coefficients (baseline). The contributions to the systematic errors from the baseline choice have been studied. The weak increase of the KK Rinv with multiplic- ity and some evidence on the decrease with kt was observed in kt range (0.2-0.8) GeV/c. For the kt dependence, the charged kaons are found to be complimentary to the neutral ones in their coverage of a larger range in kt (0.2-2.0) GeV/c and a decrease in the Rinv is observed for increasing kt as it is also seen in identical two-pion correlations in these collisions. Correlations and fluctuations / 566 Untriggered di-hadron correlations in PbPb \sqrt{s_{NN}} =2.76 TeV collisions from the ALICE experiment Anthony Timmins1 1 University of Houston We present measurements of untriggered di-hadron correlations as a function of centrality in Pb-Pb \sqrt{s_{NN}} =2.76 TeV collisions, for charged hadrons with p_{T} > 0.15 GeV/c. These measure- ments provide a map of the bulk correlation structures in heavy-ion collisions. Contributions to these structures may come from jets, initial density fluctuations, elliptic flow, and/or momentum conservation. We will decompose the measured correlation functions via a multi-parameter fit in order to extract the soft ridge; the long range \delta(\eta) correlation on the nearside observedat RHIC energies. The effect of including higher harmonics (v_{3} and v_{4}) in this procedure willbe discussed. We will compare our results to various theoretical predictions based on differing schemes for the initial conditions. Finally, we will investigate empirical scalings (such as the number of binary collisions) for the various contributions as a function of centrality, which may also help determine their origin. 203 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 82 / 567 Measurement of Upsilon suppression in Au+Au collisions at 200 GeV Shawn Whitaker1 1 Iowa State University Measuring states in the charmonium and bottomonium families is predicted to provide an indica- tion of the temperature of the quark gluon plasma. In a hot medium less tightly bound states are predicted to be dissociated at lower temperatures than the more tightly bound ground states. Understanding quarkonium suppression mechanisms of the QGP is one of the outstanding chal- lenges for theorists and experimentalists at RHIC and the LHC. PHENIX has made detailed measurements√ of J/ψ suppression in forward and in mid-rapidity. A large sample of Au+Au collisions at SNN =200 GeV was collected during 2010 data taking run at RHIC. From this sample, Upsilon mesons at mid-rapidity were identified in the di-electron decay channel and were studied to calculate their nuclear modification factor relative to that of theJψ. 143 / 568 Evaluation of the identification efficiency of the ALICE HMPID detector in p-p collisions at √s = 7 TeV by means of V0 decays Francesco Barile1 1 Universita degli Studi di Bari-Universita e INFN The ALICE experiment, dedicated to the study of heavy-ion collisions at LHC energies, featuresa high-quality particle identification system, based on the the Inner Tracking System (ITS), theTime- Projection-Chamber (TPC), the Time-of-Flight (TOF) and the HMPID. The ALICE-HMPID (High Momentum Particle Identification detector) has been designed to identify charged pions andkaons in the range 1< p <3 GeV/c and protons in the range 2< p<5 GeV/c, in a reduced region of the phase space. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, with a total active area of 11 m2, which exploit the technology of large area MWPCs equipped with Cesium Iodide (CsI) photo-cathodes for imaging the Cherenkov light emitted by a liquid C6F14 radiator. Since November 2009 ALICE is collecting p-p and Pb-Pb collisions data at LHC. A study of the particle identification efficiency of the HMPID has been carried out with samples of protons and pions coming from reconstructed V0 (Λ/anti-Λ, K0S) decays in p-p collisions at √s = 7 TeV. 82 / 569 Energy dependence of π0 suppression in Au+Au collisions Baldo Sahlmueller1; Ondrej Chvala2 1 Stony Brook University 2 UCR Riverside 204 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 0 Previous RHIC results have shown that high-pT mid-rapidity π and η mesons are suppressed in central Au+Au collisions while they are not in d+Au collisions. Furthermore, direct photons in Au+Au collisions appear mostly unsuppressed as well, with a possible exception at very high pT . This leads to the picture of a hot and dense medium in the final state. Measurements of d+Au collisions are crucial to understand the initial state in heavy-ion collisions. New d+Au data taken in 2008 improve the integrated luminosity by a factor of about 20 over the data from the 2003 run. This data set will allow much better constraints of the initial state and improve the significance of thedirect photon measurement at high pT . We will present the current status of the analysis and preliminary results on the production of π0, η, and direct photons and discuss the interpretation of the results in the light of the results from Au+Au collisions. 83 / 570 The influence of bulk evolution models on heavy-quark phenomenol- ogy Pol Gossiaux1 Hendrik van Hees 2; Jörg Aichelin 1; Marcus Bluhm 1; Min He 3; Ralf Rapp 3; Sascha Vogel 1 1 Subatech 2 Institut für Theoretische Physik, Universität Giessen 3 Cyclotron Institute and Department of Physics and Astronomy, Texas A&M University Heavy quarks are considered as one of the essential probes to study the interior of a QGP. The exper- imental observables contain only the combined information about the expansion of the system and the elementary interaction of heavy quarks with the plasma constituants. In order to asses the latter, we have to understand the influence of different expansion scenarios on the observables. In practice, models proposed by various groups for interpreting RHIC heavy quark data should be thoroughly compared before one can progress towards the understanding of LHC data. In this contribution we report on the joint effort of SUBATECH and TAMU in this respect: We study the impact ofdiffer- ent Quark-Gluon Plasma expansion scenarios in heavy-ion collisions on spectra and elliptic flow of heavy quarks. For identical heavy-quark transport coefficients relativistic Langevin simulations with different expansion scenarios can lead to appreciable variations in the calculated suppression and elliptic flow of the heavy-quark spectra, by up to a factor of two. A cross comparison withtwo sets of transport coefficients supports these findings, illustrating the importance of realistic expan- sion models for quantitative evaluations of heavy-quark observables in heavy-ion collisions. It also turns out that differences in freeze-out prescriptions and Langevin realizations play a significant role in these variations. Light-quark observables are essential in reducing the uncertainties associ- ated with the bulk-matter evolution, even though uncertainties due to the freeze-out prescription persist. Ref: arXiv:1102.1114, submitted to PRC 41 / 571 Azimuthal anisotropy of neutral pion production in Pb+Pb colli- sions at sqrt(s_NN) = 2760 GeV measured by ALICE Dmitry Blau1 1 RRC Kurchatov Institute 205 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The measurement of the azimuthal anisotropy of neutral pions athigh transverse momentum helps unveil the path-length dependence of jet-quenching. A further motivation to study this anisotropy at LHC energies is given by the fact that the azimuthal anisotropy of neutral pions at RHIC is under-predicted by current QCD energy-loss calculations. The neutral pion yield as a function of the emission angle w.r.t. the reaction plane is measured with the ALICE PHOS and EMCAL calorimeters as well as by reconstructing photons via their conversion into e+e− pairs. In addition to the azimuthal anisotropy of neutral pions the reaction plane dependence of the nuclear modification factor, RAA, is presented. 42 / 572 Modeling heavy ion collisions with CHIMERA Irakli Garishvili1 Andrew Glenn 1; Betty Abelev 1; Loren Linden Levy 1; Michael Cheng 1; Ron Soltz 1 1 Lawrence Livermore National Laboboratory Precisely determining the essential properties of QGP, such as the ratio of shear viscosity to en- tropy density, eta/s, initial temperature, T_{init}, and energy density remains among the greatest challenges in the field of heavy ion physics. To constrain these properties we have developed a software framework CHIMERA that is designed to perform statistical evaluation of multiple QGP signatures by comparing results from our multi- stage hydrodynamics/hadron cascade model of heavy ion collisions to the key soft observables (HBT, elliptic flow, spectra) measured at RHIC and LHC. All relevant data from different experiments are conveniently compiled into a single format. The unique feature of CHIMERA is that it utilizes both statistical and systematic uncertainties. The hydrodynamics/hadron cascade model used in the framework incorporates different initial state conditions, pre-equilibrium flow, the UVH2+1 viscous hydro model, Cooper-Frye freezeout, the UrQMD hadronic cascade model, and the Correlation After Burner (CrAB). To test the sensitivity of the observables to the equation of state (EoS), we use several different EoS in the hydrodynamic evolution, including those derived from the hadron resonance gas model and lattice QCD. For a particular selection of initial conditions and pre-equilibrium flow we consider T_{init}-eta/s grid. For each grid point and a particular observable we evaluate the extent of agreement between the model and experimental data by calculating chi-squared variable. The latest CHIMERA results are presented. Global and collective dynamics / 573 Identified particles from viscous hydrodynamics Denes Molnar1 1 Purdue University Much of our understanding of the collision dynamics at RHIC and LHC relies on contrasting hydrodynamic or hydro+transport calculations with 206 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / experimental data. For example, early evidence for rapid thermalization and quark-gluon plasma phase transition at RHIC came from particle spectra and the pion-proton splitting of differential elliptic flow. An inevitable component in these calculations is the conversion of the fluid to particles. For an ideal fluid the conversion is straightforward (the usual caveats of the Cooper-Frye treatment aside) because the phase space distributions are locally thermal for each species. For a viscous fluid, however, an infinite class of phase space corrections can reproduce the same hydrodynamic variables, even in a one-component system. Present viscous hydrodynamic calculations routinely assume that phase space corrections induced by shear stress are quadratic in momentum and that they have the same coefficient for all particle species (”democratic” Grad ansatz), independently of microscopic details. However, in a gas of hadrons, equilibration is driven by scattering rates - species that scatter rarely tend to be further away from local equilibrium than those that scatter often. We will present results from fully nonlinear covariant transport theory for the phase space corrections in an expanding multicomponent gas, and test the validity of Grad’s quadratic ansatz and of the “democratic” assumption for sharing viscous effects between species. The findings will be compared to phase space corrections from linear response theory, which is applicable for small gradients and small deviations from local equilibrium. Finally, we will show how dynamical phase space corrections affect basic identified particle observables (spectra and elliptic flow) in the framework of viscous hydrodynamics. 105 / 574 The Rise and Fall of the Ridge at RHIC andtheLHC Paul Sorensen1 Agnes Mocsy 2; Boris Bolliet 3; Navneet Pruthi 4; Yadav Pandit 5 1 BNL 2 Pratt Institute 3 ENS de Lyon 4 Panjab University 5 Kent State University Recent data from heavy ion collisions at RHIC show unexpectedly large near-angle correlations that broaden longitudinally with increasing centrality. The amplitude of this ridge-like correlation rises rapidly, reaches a maximum, and then falls in the most central collisions. In this talk we explain how this centrality dependence arises from an interplay between initial state density fluctuations and the almond shape of the overlap region. We show that the disappearance of the almond shape in central collisions leads to the observed reduction in the near-side ridge, uniquely linking the ridge to initial- state coordinate-space anisotropies converted into final-state momentum-space correlations. We show how the width of the ridge is related to length scales in the expanding system and we provide a prediction for the ridge amplitude in Pb+Pb collisions at √sNN = 2.76 TeV. 43 / 576 Three particle correlations as a probe of eccentricity fluctuations 207 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Jim Thomas1 1 Lawrence Berkeley National Lab The geometrical overlap region in non-central heavy ion collisions is almond shaped. Duetothis shape profile, density fluctuations for different harmonics are strongly correlated; for examplev1 and v3. If the final momentum space distributions in heavy-ion collisions depend on the initial density, then the coupling of different harmonics will lead to three particle correlations suchas cos(phi_1+2phi_2-3phi_3). In this poster√ we present STAR measurements of cos(phi_1+2phi_2-3phi_3) as a function of pt and centrality in sNN = 200 GeV Au+Au collisions. We compare our results to predictions from Teaney and Yan (1) based on ideal hydrodynamic calculations. (1) D. Teaney and L. Yan, arXiv:1010.1876v1 [nucl-th] 106 / 577 Heavy ion initial conditions and correlations between higher mo- ments in the spatial anisotropy Michael McCumber1 1 University of Colorado Fluctuations in the initial conditions for relativistic heavy ion collisions are proving to be crucial to understanding final state flow and jet quenching observables. The initial geometry hasbeen parameterized in terms of moments in the spatial anisotropy (i.e. e2, e3, e4, e5, …), and it has been stated in multiple published articles that the vector directions of odd moments are uncorrelated with both the even moments and the reaction plane angle. This poster details the results from a Monte Carlo Glauber calculation (available in arXiv:1011.1853v1) where these statements are shown to be incorrect. Instead a substantial nonzero correlation is found to be present between the even and odd moments in peripheral Au+Au collisions where the number of participating nucleons is small. The dependence of the correlation between the higher moments will be shown as a function of centrality and beam species. Global and collective dynamics / 578 Measurement of the electromagnetic dissociation cross-section of Pb nuclei at 2.76 A Tev with the ALICE ZDC Chiara Oppedisano1 1 INFN, Sezione di Torino Electromagnetic dissociation of heavy nuclei in ultra-peripheral interactions at high energies can be used to monitor the beam luminosity at colliders. Neutrons emitted by the excited nuclei close to beam rapidity are detected by the ALICE ZeroDegree Calorimeters (ZDC) with full acceptance, providing a precise measurement of the event rate. During the 2010 Pb-Pb run, a dedicated data taking has been performed triggering on electromagnetic processes with the ZDC. These data, combined with the results from the Van der Meer scan, allow one to measure the dissociation cross-section of Pb nuclei at sqrt(s)=2.76 A TeV. 208 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Experimental results on the cross-section for electromagnetic dissociation processes of Pb nuclei at the LHC will be presented together with a comparison to the available predictions. Global and collective dynamics / 581 Elliptic and triangular flow of identified particles measured with the ALICE detector. Mikolaj Krzewicki1 1 NIKHEF The anisotropic flow of identified particles is an important observable to test the collective behavior of the matter created in heavy-ion collisions. We report on the first measurements of elliptic and triangular flow for charged pions, kaons and protons in lead-lead collisions at 2.76 TeV pernucleon pair center of mass energy, measured with the ALICE detector at the LHC. We will make a detailed comparison of the observed mass splitting of v_{2} at LHC energies toRHIC measurements at lower energies. For identified particles with intermediate transverse momenta we test the quark coalescence picture with v_{2} and v_{3} scaled by the number of constituent quarks vs scaled p_{t} and scaled m_{t}. 23 / 582 Jet production measurements with the ALICE Experiment in pp collisions at the LHC Sidharth Kumar Prasad1 1 Wayne State University [email protected], [email protected] Measurements of inclusive jet production cross sections in proton-proton (pp) collisions provide a direct test of predictions of perturbative quantum chromodynamics. They also provide a baseline for measurements in heavy ion collisions. Jets are the collimated spray of particles originating from the fragmentation of hard scattered partons in the collision. They are defined by clustering algorithms in each event and represent the physical properties of partons from the hard scattering. It is therefore important to understand the performance of clustering algorithms that can be used in pp and A-A collision studies. The ALICE detector at the LHC has excellent tracking capabilities for charged particles overawide range of transverse momenta and can be used for studying jet properties. We will present the per- formance of kt, anti-kt, SISCone and UA1 cone finder clustering algorithms for charged particle jet reconstruction using the ALICE detector at midrapidity in proton-proton collisions at the LHC. We will also compare our results with PYTHIA simulations. 34 / 583 Measurement of Charge Multiplicity Asymmetry Correlations to Search for Chiral Magnetic Effect in Heavy Ion Collisions by STAR 209 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Quan Wang1 1 Purdue University It has been suggested that local parity violation in QCD would lead to charge separation of quarks by the Chiral Magnetic Effect (CME) in heavy ion collisions. Charge separation could yield a dynamical charge multiplicity asymmetry with respect to the reac- tion plane. In this poster, we√ report results on charge multiplicity asymmetry correlations in sNN = 200 GeV Au+Au and d+Au collisions by the STAR experiment, as well as from the RHIC beam energy scan. We found that the correlation results could not be explained by CME alone. To gain further insights, we study our results as a function of the measured azimuthal angle range as well as the event-by-event anisotropy parameter v2. The results indicate that the charge separation effect appears tobe in-plane rather than out-of-plane. We found that the charge separation effect is proportional to the event-by-event v2 and consistent with zero in events with v2 ≈ 0. Our studies suggest that the charge separation effect, within the statistical error, may be a net effect of event anisotropy and correlated particle production. Possible upper limit on the CME imposed by our data will be discussed. 584 Ridge Studies in Pb+Pb Collisions at the LHC based on Number and Transverse Momentum Two-Particle Correlation Functions Claude Andre Pruneau1 1 Wayne State University-Unknown-Unknown Observations of a ridge on the near-side, and a dip on the away-side of two-particle correlations measured in central Au + Au collisions have generated considerable interest at RHIC. Are the two phenomena connected? Do they result from jet interactions with the medium, or do they naturally arise from the rapid thermalization and hydrodynamic expansion of collision systems subject to large initial fluctuations? We present measurements, carried with the ALICE detector, of number (R2) and transverse momen- tum (∆pt∆pt) correlation functions in Pb + Pb collisions. The two correlation functions are studied as a function of collision centrality for ++, -\ -, and +- charged particle pairs in various momentum ranges. The like-sign and unlike-sign correlations exhibit a different evolution with collision cen- trality. We combine these correlations to study charge dependent (CD) and charge independent (CI) correlation functions. We characterize these distributions by studying Fourier decompositions of ∆φ projections of the R2 and ∆pt∆pt correlation functions for different ranges of ∆η. Of partic- ular interest are the evolution of the ratios of 3rd, and 4th harmonics to the 2nd harmonics with number of participants. We will discuss these results in light of a MC Glauber model of the initial eccentricity of collision nucleon participants. 107 / 585 Charge Fluctuations in Pb-Pb Collisions at √sNN = 2.76 TeV mea- sured by ALICE experiment Satyajit Jena1 210 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 IIT Bombay Charge fluctuations are considered to provide a possible signature for the existence of the de-confined Quark Gluon Plasma phase (QGP). Charge fluctuations are sensitive to the number of charges inthe system, thus the fluctuations in the QGP, with fractionally charged partons, are significantly differ- ent from those of hadron gas with unit charged particles [1,2]. The study of charge fluctuations have been carried out by using the variable, ν+-,dyn [3] which, by its construction, is free from the col- lisional bias, i.e., impact parameter fluctuations and fluctuations from the finite number of charged particles within the detector acceptance. The dependence of charge fluctuations on the rapidity win- dows for various centrality bins are analyzed for Pb+Pb collisions at √sNN =2.76 TeV in the ALICE experiment at CERN-LHC. A scaling behavior is observed as a function of increasing pseudo-rapidity window for the charge fluctuations, expressed in terms of Nch x ν+-,dyn, where Nch is thenumber of charged particles. The observed fluctuations are corrected for diffusion of fluctuations [4,5]inthe hadronic medium. The results will be shown and discussed. [1] S. Jeon, V. Koch, Phys. Rev. Lett. 85 (2000) 2076 [2] M. Asakawa,U.W. Heinz, and B. Muller, Phys. Rev. Lett., 85 (2000) 2072 [3] C. Pruneau, S. Gavin, and S. Voloshin, Phys.Rev.C66:044904,200 [4] E. V. Shuryak and M. A. Stephano, Phys. Rev. C63 (2001) 064903 [5] M. A. Aziz and S. Gavin, Phys. Rev. C70 (2004) 034905. 158 / 586 Towards the phase diagram of QCD Rainer Stiele1 Jan M. Pawlowski 1; Jürgen Schaffner-Bielich 1; Lisa Marie Haas 1 1 Institute for Theoretical Physics, Heidelberg University Lattice computations as well ab initio continuum QCD calculations show a broad crossover forboth chiral symmetry restoration and the deconfinement transition at vanishing density. Particularly, the change of the order parameter for deconfinement, the Polyakov loop, occurs in a rather broad temperature interval. In contrast, current Polyakov loop extended effective models show steeper slopes in a smaller transition region. Moreover, the critical temperatures show some dependence on the chosen Polyakov loop potential. We qualitatively improve these models towards full QCD by adjusting the Polyakov loop potential to the full glue potential of continuum ab initio computations. We present results for the phase structure of QCD at finite density derived from these improved models. Correlations and fluctuations / 587 Femtoscopy of the system shape fluctuations in heavy ion colli- sions Sergei Voloshin1 1 Department of Physics and Astronomy-College of Science-Wayne Sta The system created in a heavy ion collision in general is not azimuthally symmetri; moreover, the initial spatial distribution, e.g. that of the energy density, fluctuates event-by-event even at fixed im- pact parameter. Because of particle interactions, this initial spatial asymmetry leads to anisotropies 211 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / in particle emission – the phenomenon called anisotropic flow. The best known anisotropy ofthis kind is the elliptic flow that is described by the second harmonic in particle azimuthal distribution. Recently, the so-called triangular, and higher harmonic flow, and in particular their sensitivity tothe system initial conditions attracted a lot of attention, as they might provide additional important in- formation about the initial conditions and dynamical properties (e.g. viscosity) of the system. Fluctuations in the initial geometry should be also reflected in the detail shape of the system at freeze-out. In this talk I discuss the possibility to measure such fluctuations by means of identical and non-identical particle femtoscopy. I support my conclusion on the sensitivity of the method to measure triangularity and higher harmonic spatial asymmetries by analytical calculations, and by results from event generators and blast wave model calculations. Correlations and fluctuations / 588 Two-pion Bose-Einstein correlations in PbPb collisions at 2.76 TeV with ALICE Jorge Mercado1 1 Heidelberg University We present the first measurement of pion source radii in Pb-Pb collisions at the LHC. The radii were obtained by analyzing the Bose-Einstein enhancement in two-pion correlation functions. Like at lower energies, the radii drop with increasing transverse momentum, indicating the presence of collective expansion. In absolute terms, all three radii (R_out, R_side, R_long) are larger than at RHIC, roughly consistent with a linear scaling with the cube root of the particle multiplicity. The results, taken together with those obtained from the study of the multiplicity and the azimuthal anisotropy, indicate that the fireball formed in nuclear collisions at the LHC is hotter, lives longer, and expands to a larger size as compared tolower energies. Jets / 589 Probing nuclear matter with jets and γ-hadron correlations: re- sults from PHENIX Nathan Grau1 1 Augustana College Fully reconstructed jets and hadrons correlated with a direct photon significantly reduce energy- loss bias, the bias toward measuring particles from partons which suffer little energy loss. In d+Au collisions, one accesses the physics at large x, which yields important constraints for nuclear par- ton distribution functions. In both d+Au and A+A collisions, coherent multiple-scattering models of energy loss can be tested. In this contribution, we present the current results from the PHENIX experiment on fully reconstructed jets and direct γ-hadron correlations. Baseline measurements of jets in p+p collisions as well as their yield and correlation modifications in d+Au and Cu+Cu will be given. From γ-hadron correlations, we present the fragmentation function in p+p and Au+Au collisions and its modification in Au+Au to lower zT than what has previously been studied. Impli- cations of this data on our understanding of both cold and hot, dense nuclear matter created at RHIC are discussed. 212 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 108 / 590 Status of the Search for Hadronic Squeezed Correlations at RHIC Energies Sandra S. Padula1 Danuce M. Dudek 1; Otavio Socolowski, Jr. 2 1 Instituto de Fisica Teorica (IFT)-Univ. Estadual Paulista, SP, Brazil 2 IMEF - Univ. Federal de Rio Grande, RS, Brazil The hot and dense medium formed in high energy heavy ion collisions may induce shifts ofhadronic masses from their asymptotic values. In case this mass modification indeed occurs, it was demon- strated that squeezed correlations of particle-antiparticle pairs, also known as Back-to-Back Correla- tions (BBC), should appear. They are expected either in the bosonic (bBBC) or in the fermionic (fBBC) cases [1], in both being positive correlations of unlimited intensity, even for finite-size systems ex- panding with moderate flow [2]. Although they could nicely probe the mass shift with asymptotic particles, these hadronic squeezed correlations are very sensitive to the functional form of their time emission distribution. This strong sensitivity was demonstrated in [1], by comparing thesud- den emission with a Lorentzian distribution, which reduced the intensity of the effect by orders of magnitude. We show here that the reduction of the signal is even more dramatic if this time emission is parameterized by a Levy-type of distribution [3], although it could still survive if the duration of the process is short and if we search for the effect with lighter mesons, such as kaons. To experimentally search for the BBC signal, we have suggested to look for the particle-antiparticle ⃗ squeezed correlation function, plotted in terms of the average momentum of thepair, K⃗ 12 = (k1 + ⃗ ⃗ ⃗ k2)/2, for high values of their relative momentum, ⃗q12 = (k1 −k2) [4]. The first experimental search for the squeezed particle-antiparticle correlations was shown for different hadron pairs in Ref. [5]. We compare here such preliminary results with predictions of our model for K +K− pairs, showing that the outcome of the experimental search may be still inconclusive, however it does not deny the existence of the squeezing effect on kaons produced at RHIC energies with in-medium modified masses. [1] M. Asakawa, T. Csorgo, M. Gyulassy, Phys. Rev. Lett. 83, 4013 (1999); P. K. Panda, T. Csorgo, Y. Hama, G. Krein, and Sandra S. Padula, Phys. Lett. B 512, 49 (2001). [2] Sandra S. Padula, G. Krein, T. Csorgo, Y. Hama, and P. K. Panda, Phys. Rev. C 73, 044906 (2006). [3] Danuce M. Dudek and Sandra S. Padula, Phys. Rev. C 82, 034905 (2010). [4] Sandra S. Padula, O. Socolowski Jr., T. Csorgo and M. I. Nagy, Proc. Quark Matter 2008, J. Phys. G: Nucl. Part. Phys. 35, 104141 (2008); Sandra S. Padula and Otavio Socolowski Jr., Phys. Rev. C 82, 034908 (2010). [5] Marton Nagy (for√ the RHIC/PHENIX Collaboration) “Particle-antiparticle back-to-back correla- tion measurement in sNN = 200 GeV Au+Au collisions”, WPCF 2009, https://indico.cern.ch/conferenceTimeTable.py?confId=54173#all . Heavy Flavors / 591 √ D meson nuclear modification factors in PbPb collisions at sNN = 2.76 TeV, measured with the ALICE detector Andrea Rossi1 1 Sezione di Padova (INFN)-Universita e INFN 213 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The comparison of heavy flavour production in proton-proton and heavy-ion collisions allowsto probe the properties of the high-density QCD medium formed in the latter and to study the mech- anism of in-medium partonic energy loss. The √ALICE experiment has measured√ the D meson pro- duction in pp and Pb–Pb collisions at the LHC at s = 7 and 2.76 TeV and sNN = 2.76 TeV respectively, via the exclusive reconstruction of hadronic decay channels. The D meson decay ver- tices, displaced by few hundred microns from the main interaction point, are selected by exploiting the high-resolution tracking performance and the hadron identification capabilities of the ALICE detectors. The analyses of the D0 → K−π+ and D+ → K−π+π+ channels will be described and the preliminary results for the D0 and D+ nuclear modification factor will be presented. 44 / 592 Transverse momentum distributions of pions, kaons and protons for high multiplicity and close to azimuthal isotropic events in 7 TeV pp collisions with the ALICE experiment at the LHC Cristian Andrei1 1 National Institute of Physics and Nuclear Engineering (IFIN-HH)- Studies on transverse momentum (pt) distributions, the mean pt values and yield ratios of pions, kaons and protons at mid rapidity (|y|<0.5) for different charged particle multiplicities and event shapes in pp collisions at √s=7 TeV are reported. The changes in the shape of the pt distribution of pions, kaons and protons as a function ofcharged particle multiplicity and degree of azimuthal isotropy of the considered events are investigated. The mean pt of identified particles, increasing with particle mass, are presented as a function of multiplic- ity and event shape and compared with PYTHIA and PHOJET model predictions. The particle ratios as a function of pt for high multiplicity and close to azimuthal isotropic class of events are compared to the minimum bias case. An attempt is also made for extracting an average transverse energy density and, under several model assumptions, comparing it to the ones of heavy-ion collisions at RHIC and LHC energies. 45 / 593 Rapidity and centrality dependence of identified hadrons in Au+Au and p+p collisions at 200 GeV Catalin for BRAHMS Collaboration Ristea1; Oana Ristea1 1 University of Bucharest The BRAHMS collaboration has measured identified particles from AuAu and pp collisions at200GeV over 3 units of rapidity. We will investigate the scaling of pion and kaon production with Ncoll and Npart at both central and forward rapidities. The kaon to pion ratio serves as a measure of equilibration of strange quarks. BRAHMS hasfound that for central collisions the K-/K+ ratio is strongly correlated to the pbar/p ratio. We will show how this correlation evolves with the centrality of the system. We will also show the centrality dependence of R_AA(Pt) at both central and forward rapidity for both mesons and baryons. For central collisions BRAHMS has already shown that R_AA does not depend strongly on rapidity 214 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / but these data represent the first time that the centrality dependence of R_AA has been measured at forward rapidity. These data thus provide a summary of hadron production over a very wide rapidity and centrality range. 133 / 594 Development of the FARICH detector as a possible upgrade for ALICE HMPID system Alexeii Kurepin1 Alexander Danilyuk 2; Alexey Onuchin 3; Andrey Reshetin 1; Dmitry Finogeev 4; Evgenij Usenko 1; Evguenij Kravchenko 3; Sergey Kononov 3; Vladimir Razin 1 1 Institute for Nuclear Research (INR) 2 Boreskov Institute of Catalysis 3 Budker Institute of Nuclear Physics 4 nstitute for Nuclear Research (INR Development of the FARICH detector as a possible upgrade for ALICE HMPID system A.B. Kurepin a, A.I. Reshetin a, A.F. Danilyuk c, D.A. Finogeev a, T.L. Karavicheva a, E.V. Karpechev a, V.L. Kirillov c, S.A. Kononov b, E.A. Kravchenko b, A.N. Kurepin a, A.I. Maevskaya a, Yu.V. Musienko a, A.P. Onuchin b, V.I. Razin a, N.S.Topilskaya a, E.A.Usenkoa a. Institute for Nuclear Research of the Russian Academy of Sciences, 117312 Moscow, Russia b. Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosi- birsk, Russia c. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia Abstract As a possible upgrade of the ALICE experiment the construction of the Focusing Aerogel Ring Imaging Cherenkov (FARICH) detector is proposed. The goal of the FARICH is to extend the working momentum range of the charged particle iden- tification at ALICE for a high transverse momentum PT region up to 10 GeV/c for thepion–kaon separation and up to 15 GeV/c for kaon–proton separation. It will enable to provide better conditions for the investigation of the parton-medium effects at LHC energies. In this report the FARICH detector concept and possible detector construction on the basis of a multi- layer aerogel radiator and photosensitive MRS APD focal plane are presented. The main idea of the FARICH detector development is to employ a Cherenkov radiator composedof several aerogel layers with different index of refraction. Index of refraction of each layer is gradually increased along the particle direction, so that Cherenkov ring images produced by different layers coincide in the focal plane and form more narrow ring image. Simulation was made for a multi-layer radiator based on the Geant4 software toolkit. Results of the FARICH prototype test on the 6 GeV/c negative pion beam of the CERN PS T10 test channel are presented and discussed. Taking into account the FARICH prototype geometrical efficiency the FARICH Cherenkov angle resolution of about 2,1 mrad was obtained. 159 / 595 Droplets in the cold and dense chiral phase transition 215 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Leticia Palhares1 Eduardo Fraga 2 1 CEA/Saclay 2 IF-UFRJ The linear sigma model with quarks at very low temperatures provides an effective description for the thermodynamics of the strong interaction in cold and dense matter, being especially useful at densities found in compact stars and protoneutron star matter. Using the MSbar one-loop effective potential, we compute quantities that are relevant in the process of nucleation of droplets of quark matter in this scenario. In particular, we show that the model predicts a surface tension of\Sigma ~ 5-15 MeV/fm^2, rendering nucleation of quark matter possible during the early post-bounce stage of core collapse supernovae. Including temperature effects and vacuum logarithmic corrections, we find a clear competition between these features in characterizing the dynamics of the chiralphase conversion, so that if the temperature is low enough the consistent inclusion of vacuum corrections could help preventing the nucleation of quark matter during the collapse process. We also discuss the first interaction corrections that come about at two-loop order. 109 / 596 Long-Range (Forward-Backward) Pt and Multiplicity Correlations in pp Collisions at 0.9 and 7 TeV Grigori Feofilov1 2 1 2 1 St. Petersburg State University 2 3 Long-Range (Forward-Backward) Pt and Multiplicity Correlations in pp Collisions at 0.9 and 7 TeV The ALICE Collaboration (Submitted by Grigory Feofilov) Long-range rapidity and azimuthal correlations (LRC) of charged particles are a sensitive tool to study the initial conditions for the Quark Gluon Plasma (QGP) formation [1],[2],[3]. Measured in separated pseudorapidity intervals, these correlations, if they exist, mainly Pt- Nch and Pt-Pt, could be the indication in case of pp collisions of processes like color string fusion[2] or glasma flux tubes formation[3]. The event-by-event analysis of the long-range Forward-Backward (FB) Nch-Nch, Pt-Nch and Pt-Pt correlations has been performed on data of the ALICE experiment obtained in the pp runs at 0.9 and 7 TeV pp collision energies. The following observables were defined: Pt (the average transverse momentum in theevent) and Nch (the event multiplicity of charged particles). Two pseudorapidity intervals (the “forward” and the “backward” windows) of the variable width from 0.2 to 0.8 rapidity units were chosen. Correlations were studied as a function of the width of these windows and on the gap between them, as well as for the different configurations of four pi/2 azimuthal sectors relevant to these windows. Methods for separating the short-range correlations and to measure the long-range correlations strength in the limited acceptance of the ALICE central barrel (-0.8, 0.8) are discussed. Analysis results show a behaviour compatible with LRC phenomena for these pp collisions. They are compared to PYTHIA and to the model with independent emitters (strings) [4]. References [1] Abramovskii V. A., Gedalin E. V., Gurvich E. G., Kancheli O. V. , JETP Lett., vol.47, 216 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 337-339 , 1988. [2] M.A.Braun, C.Pajares, Phys.Lett. B287 (1992) 154; Nucl.Phys. B390 (1993) 542; Eur.Phys.J. C16 (2000) 349; N.S.Amelin, N.Armesto, M.A.Braun, E.G.Ferreiro, C.Pajares, Phys.Rev.Lett. 73 (1994) 2813; M.A.Braun, C.Pajares, V.V.Vechernin, Phys.Lett. B493 (2000) 54; Internal Note/FMD, ALICE-INT-2001-16, CERN, Geneva (2001) 13p.; M.A.Braun, R.S.Kolevatov, C.Pajares, V.V.Vechernin, Eur.Phys.J. C32 (2004) 535; V.V.Vechernin, R.S.Kolevatov, Phys. of Atom.Nucl. 70 (2007) 1797; 1809. [3] L.McLerran, “The Color Glass Condensate and the Glasma”, Proceedings of theInter- national School of Subnuclear Physics, Subnuclear Series, Vol. 45, 2010. [4] V.V. Vechernin, arXiv:1012.0214, 2010. Pre-equilibrium and initial state / 597 Cold nuclear matter physics at low-x from d+Au collisions at PHENIX Mickey Chiu1 1 Brookhaven National Lab RHIC experiments have observed that inclusive√ hadron yields in the forward rapidity (deuteron) direction for sNN = 200 GeV d+Au collisions are suppressed relative to p+p collisions. The mechanism for the suppression has not been firmly established; theoretical descriptions include nuclear shadowing, initial-state parton energy loss, and gluon satu- ration. We present measurements by the PHENIX experiment at RHIC of di-hadron pair production in d+Au collisions where the particles in the pair are varied across a wide range of rapidity out to |η| = 3.8 using a new forward electromagnetic calorimeter, the MPC. These di-hadron measurements probe down to parton momentum fractions x ~ 10−3 in the gold nucleus, where the interesting possibility of observing gluon saturation effects at RHIC is the greatest. Our measurements show that the correlated yield of back-to-back pairs in d+Au collisions is suppressed by up to an order of magnitude relative to p+p collisions, and increases with greater nuclear path thickness and with decreasing parton x in the Au nucleus. 24 / 598 Jets and Underlying Events in p+p Collisions at LHC energies Andras Gabor Agocs1 Gergely Barnafoldi 1; Peter Levai 1 1 KFKI Research Institute for Particle and Nuclear Physics Jet matter interaction remains a central question and a theoretical challenge in heavy-ion physics and might become important in high-multiplicity events in proton-proton collisions at LHC energies. Full jet measurements at LHC are hoped to reconstruct the complete energy loss process and fragmentation of the hard parton in the medium. Since, jet reconstruction will be constrained to small cone sizes, study of the connection between jets and their underlying event could provide a differential tool combined with particle identification in a wide momentum range. 217 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Global and collective dynamics / 599 Charged-particle multiplicity, centrality and the Glauber model with ALICE at 2.76 ATeV Constantinos Loizides1 1 Lawrence Berkeley National Lab. (LBNL) The measurements of charged-particle multiplicity and transverse energy in Pb-Pb collisions at 2.76 ATeV are reported as a function of centrality. The fraction of inelastic cross section seen by the ALICE detector is estimated using a Glauber model or correcting the data by simulations. The results scaled by the number of participating nucleons are compared with ppcol- lisions at the same collision energy and to similar results obtained at the significantly lower energies, and with models based on different mechanisms for particle production in nuclear collisions. Partic- ular emphasis will be given to a discussion on systematic studies of the dependence of the centrality determination on the Glauber model, and the validity of the Glauber model at 2.76 TeV. 144 / 600 Coulomb effects in relativistic heavy ion collisions from CBMex- periment Oana Ristea1 1 University of Bucharest, Faculty of Physics At AGS and SPS energies, the ratio of negative to positive pions at low pion transverse momenta reflects the effect of Coulomb repulsion, because the charged particles, especially pions, arehighly influenced by the Coulomb field produced by the net charge of the reaction protons. Theinteraction between charged pions and net charged of protons changes the transverse momentum of pions with a Coulomb momentum or Coulomb „kick”. We will use simulated Au+Au data with HIJING and UrQMD codes, as well as other suited MC models, in order to obtain this Coulomb “kick” for the collision systems detected with future CBM (Compressed Baryonic Matter) experiment at FAIR available energies. The predictions for Coulomb “kick” at CBM will be compared with 200 GeV Au+Au results. 3 / 601 Exact analytic hydrodynamical results and estimations of the ini- tial conditions in p+p and Pb+Pb collisions at LHC Márton Nagy1 Máté Csanád 2; Tamás Csörgő 1 1 MTA KFKI RMKI, H-1525 Budapest 114, P.O.Box 49, Hungary 2 Dept. Atomic Physics, ELTE University, Budapest, Hungary 218 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Simple and exact solutions of relativistic hydrodynamics are presented, including the first exact solution of relativistic hydrodynamics with non-zero total angular momentum, an important characteristics of mid-central and peripheral heavy ion collisions. The consequences of these new solutions are explored in data analysis. The effects of longitudinal work, acceleration andthe rotation of the fluid are taken into account in an advanced estimate of the initial energy density, temperature, pressure and the life-time of the reaction. This advanced estimate of the initial energy density yield values that are significantly larger in Pb+Pb collisions at LHC energies thanthe 15 GeV/fm**3 initial energy densities obtained from Bjorken’s estimate. References: M. I. Nagy, http://arxiv.org/abs/0909.4285, Phys. Rev. C (2011) in press M. I. Nagy, T. Csörgő, M. Csanád, Phys.Rev.C77:024908,2008 T. Csörgő, M. I. Nagy and M. Csanád, J.Phys.G35:104128,2008, Phys.Lett.B663:306-311,2008 Future facilities and experiment upgrades / 602 Cross section normalization in ALICE Ken Oyama1 1 University of Heidelberg Measurements of reference trigger cross sections were obtained with the ALICE detector, based on beam properties measured from van der Meer scans where convolution of the beam profiles were evaluated. The measurement is essential for absolute cross section determination of the physics processes. Based on this measurement, inelastic cross sections characterizing proton-proton collisions at LHC energies were obtained with the ALICE detector with a detailed detector Monte-Carlo simulations. As second example, cross sections of reference process, with at least one charged particle√ is produced in pseudorapidity range of −0.8 < η < 0.8, was measured. These results obtained for s=2.76 TeV and 7 TeV are compared to measurements from other experiments as well as to recent calculations based on Regge theories for inelastic cross sections. The detail descriptions of thees measurements and analysis methods will be presented. Thepresen- tation will focuses also on instrumental and technical aspects of detectors and accelerators. 145 / 603 Proposal of new super-compact calorimeter design for the for- ward physics Libor Skoda1 219 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Jan Cepila 1; Jaroslav Adam 1; Michal Petran 1; Vojtech Petracek 1 1 FNSPE CTU in Prague Forward rapidity region of the high energy particle collisions affords opportunities for studying more details of physics at small Bjorken-x. Measurement of this region within the existing particle experiments is often restricted due to existing framework and limited space. The aim of our project is therefore to develop new super-compact ECAL for the forward region based on the tungsten- scintillator calorimeter. The active element of the calorimeter was chosen to be longitudinally ori- ented thin scintillator cards consisting of variable granularity pads with optical readout. Design allows for operation in high multiplicity environment close to y=4.5 and due to its compactness pro- vides also possibility to include HCAL part. Optical readout can operate at high trigger rates and system is able to generate L0 trigger. 84 / 604 Measurement of electrons from heavy-flavor decays in p-p and Pb-Pb collisions with the ALICE EMCAL Shingo Sakai1 1 Lawrence Berkeley National Lab. (LBNL) High pT heavy flavor (charm and beauty) production is an important probe of partonic energy loss in hot QCD matter. Measurement of the suppression of heavy flavor decay electrons production in nuclear collisions will reflect the energy loss of the parent heavy quarks. We present the analysis strategy and first results for inclusive heavy flavor decay electrons produc- tion in proton-proton collisions at ¥sqrts = 7 TeV and Pb-Pb collisions at ¥sqrtsNN = 2.76 TeV by the ALICE experiment, utilizing the large acceptance ALICE Electromagnetic Calorimeter. 68 / 605 Hadron-Resonance Correlation in pp collisions at the LHC with ALICE Dilan Madagodahettige Don1 1 University of Houston The Width and the mass of short lived resonances are sensitive to the medium properties during the phase transition from the deconfined partonic phase to the confined hadronic phase. Heavy hadrons have a larger probability to be produced within the quark gluon plasma phase due to their short formation times. Heavy mass, high momentum resonances from jet fragmentation are more likely to be affected by the chirally symmetric medium, and the identification of the early produced resonances from jet fragmentation might be a viable option to study chirality [1]. Two particle corre- lations in di-jet cones can be used to distinguish between in-medium and in-vacuum fragmentation by assuming that the nearside correlations are surface biased whereas the away-side of a di-jet is likely interacting with the partonic medium. In the analysis a single high pt hadron is chosen as a jet leading particle. Then the correlations of 220 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / phi(1020) and K*(892), identified by their hadronic decay, with this leading particle have been stud- ied in pp collisions at 7 TeV. The characteristics of these resonances (mass and width) as a function of the resonance correlation angle have been extracted both on the near side and the away side. References [1] C. Markert, R.Bellwied, I.Vitev, Phys. Lett B699 92-97 114 / 606 Di-electron analysis in Au+Au collisions using the PHENIX Hadron Blind Detector Ermias T. Atomssa1 1 Stony Brook University The di-electron spectrum is rich with physics signals that assist the characterisation of themedium created in A+A collisions. The measurement, especially at low mass, is however complex duetoa very low signal to background ratio. PHENIX has shown in the past that despite this difficulty, it is possible to learn for example about open charm production [1] or direct photons [2]. The Hadron Blind Detector (HBD) was built, installed and operated by PHENIX with the objectiveof reducing the combinatorial background of the di-electron spectrum. This background comes mainly from conversions and Dalitz decay electrons, most significantly, when one leg of the pair was swept out of the acceptance by the magnetic field, and thus contributes only to the combinatorial back- ground. Current status of the efforts in analyzing the data taken with this detector in Au+Au collisions at200~GeV will be shown. References [1] Phys. Lett. B 670, 313 (2009) [2] Phys. Rev. Lett. 104, 132301 (2010) 607 Effect of running coupling on photons from jet - plasma interac- tion in relativistic heavy ion collisions Lusaka Bhattacharya1 1 Saha Institute of Nuclear Physics We discuss the role of collisional energy loss on high pT photon data measured by PHENIX collaboration by calculating photon yield in jet-plasma interaction. The phase space distribution of the participating jet is dynamically evolved by solving Fokker-Planck equation. We treat the strong coupling constant (αs) as function of momentum and temperature while calculating the drag and diffusion coefficients. It is observed that the quenching factor is substantially modified as compared to the case when αs is taken as constant. It is shown that the data is reasonably well reproduced when contributions from all the relevant sources are taken into account. Predictions at higher beam energies relevant for LHC experiment have been made. 221 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 608 Nuclear modification factor in an anisotropic Quark-Gluon-Plasma Lusaka Bhattacharya1 1 Saha Institute of Nuclear Physics We calculate the nuclear modification factor (RAA) of light hadrons by taking into account the initial state momentum anisotropy of the quark gluon plasma (QGP) expected to be formed in relativistic heavy ion collisions. Such an anisotropy can result from the initial rapid longitudinal expansion of the matter. A phenomenological model for the space time evolution of the anisotropic QGP is used to obtain the time dependence of the anisotropy parameter ξ and the hard momentum scale, phard. The result is then compared with the PHENIX experimental datato constrain the isotropization time scale, τiso. It is shown that the extracted value of τiso lies in the range 0.5 ≤ τiso ≤ 1.5. The present calculation is also extended to contrast with the recent measurement√ of nuclear modification factor by ALICE collaboration at s = 2.76 TeV. It is argued that similar values of τiso are closer to the data. The sensitivity of the results on the initial conditions has been discussed.√ We also present the nuclear modification factor at LHC energies with s = 5.5 TeV. Heavy flavor / 609 Open heavy flavor physics in the muon channel with ALICE in pp collisions at 7 TeV and PbPb at 2.76 TeV Xiaoming Zhang1 1 Laboratoire de Physique Corpusculaire, Clermont-Ferrand Heavy-quark production is one of the probes for the investigation of the properties of the high-density medium formed in heavy-ion collisions. This investigation requires also the study of proton-proton collisions. Besides providing the necessary baseline for nucleus-nucleus collisions, proton-proton collisions are of great interest, also in their own right, since they allow to test perturbative QCD at unprecedented low Bjorken-x values. In this contribution, we measure the heavy-flavour production by detecting single muons from semi-leptonic decays. After a description of the ALICE muon spectrometer, we will present the results onthe production of single muons from heavy flavour decays at forward rapidity (2.5 < y < 4) in pp collisions at Heavy-quark production is one of the probes for the investigation of the properties of the high-density medium formed in heavy-ion collisions. This investigation requires also the study of proton-proton collisions. Besides providing the necessary baseline for nucleus-nucleus collisions, proton-proton collisions are of great interest, also in their own right, since they allow to test perturbative QCD at unprecedented low Bjorken-x values. In this contribution, we measure the heavy- avour production by detecting single muons from semi-leptonic decays. After a description of the ALICE muon spectrometer, we will present the results onthe production of single muons from heavy avour decays at forward rapidity (2:5 < y < 4) in pp collisions at √s = 7 TeV and Pb-Pb collisions at Heavy-quark production is one of the probes for the investigation of the properties 222 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / of the high-density medium formed in heavy-ion collisions. This investigation requires also the study of proton-proton collisions. Besides providing the necessary baseline for nucleus-nucleus collisions, proton-proton collisions are of great interest, also in their own right, since they allow to test perturbative QCD at unprecedented low Bjorken-x values. In this contribution, we measure the heavy- avour production by detecting single muons from semi-leptonic decays. After a description of the ALICE muon spectrometer, we will present the results onthe production of single muons from heavy avour decays at forward rapidity (2:5 < y < 4) in pp collisions at √s = 7 TeV and Pb-Pb collisions at √sNN = 2.76 TeV. In particular, we will show the pt-dierential production cross section in pp collisions and compare it to perturbative QCD predictions, and the nuclear modication factors in Pb-Pb collisions. RAA with respect to a pp reference at √s = 2.76 TeV and RCP in central with respect to peripheral collisions. 46 / 610 Underlying Event measurement in pp collisions with the ALICE experiment at LHC Sara Vallero1 1 Physikalisches Institut - University of Heidelberg In a pp collision the jet signature has to be decoupled from the soft or semi-hard bulk of particles origi- nating from beam-remnant fragmentation, initial and final state radiation and multi-partonicinteractions: the so-called Underlying Event. Besides being a baseline for jet studies, its characterization provides insight into the non-perturbative phenomenology in high energy collisions and, in particular, it is a powerful tool to tune Monte Carlo event generators. We studied the underlying activity in two transverse regions azimuthally perpendicular to the leading track in the event. The relevant observ- ables for this analysis are the multiplicity and sum pT densities of charged particles. We present these Underlying Event distributions as measured by the ALICE collaboration at collision energies of 0.9 and 7 TeV. Three different values of track pT cut-off are considered: 1.0, 0.5 and 0.15 GeV/c. Data are fully corrected to the particle leveland compared to a selection of Monte Carlo models. 47 / 612 Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV, 2.76 TeV and 7 TeV, with ALICE at LHC Jean-Pierre Revol1 1 CERN High-statistics measurements were performed at LHC, with the ALICE central barrel detectors, in the central pseudorapidity region (–1 ≤ η < 1) of multiplicity distributions, and pseudorapidity densities of primary charged particles produced in proton–proton collisions, at √s = 0.9 TeV, 2.76 TeV and 7 TeV. Measurements were obtained for two event classes: inelastic events (INEL) and non-single diffractive events (NSD). The data are compared to measurements from other experiments and to simulations with Monte Carlo event generators PYTHIA and PHOJET. 223 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Correlations and fluctuations / 613 Initial condition fluctuations in heavy ion collisions Philippe Mota1 Dirk Rischke 2; Takeshi Kodama 3 1 Institut für Theoretische Physik, Goethe-Universität 2 Institute for Theoretical Physics, Goethe University 3 Universidade Federal do Rio de Janeiro We investigate the effect of event-by-event fluctuations and the degree of granularity in the initial conditions on the collective evolution of matter created in heavy-ion collisions using fluid dynamics. Motivated by the glasma-flux-tube scenario, we model the initial condition by a set of randomly distributed longitudinal tubes in a boost-invariant 2D geometry. The model introduces two param- eters: the number of tubes in each event and the transverse (gaussian) width in energy density of a tube. The number of tubes fluctuates event by event and the width of the tubes introduces agran- ularity to the initial condition. Both parameters strongly affect the hydrodynamical evolution. For instance, we observe that the increasing granularity reduces the slope of the transverse momentum spectra, decreases the value of the differential elliptic flow at the average transverse momentum, and generates a double-peak structure in the two-particle distribution. With this framework, we aim to constrain the initial condition of a heavy-ion collision by performing a systematic analysis of the effects of each parameter on the final observables. 48 / 614 Detector effects and systematic uncertainties in the directed flow measurement with spectator neutrons in ALICE at LHC. Gyulnara Eyyubova1 1 University of Oslo Directed flow serves as one of the key observable to understand the properties of the hot and dense matter produced in ion-ion collisions. We report on systematics and detector effects study in the directed flow measurement using the reaction plane estimate provided bythe sidewards deflection of neutral spectators measured with the help of ALICE Zero Degree Calorimeter detectors. Effects from variation in the beam crossing parameters on the reaction plane resolution are studied via cross correlations between spectator deflection in the plane transverse to the beam direction. Systematic uncertainties of the measured signal are assessed by comparing results from different flow measurement techniques, such as the scalar product and the eventplane methods. 146 / 615 The ALICE EMCal Overview and Status Bjorn Nilsen1 1 Creighton University 224 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / An overview of the ALICE EMCal, as installed and operating in 2011, will be presented. Features of the EMCal construction, acceptance and operation will be described together with details of the calibration and performance of the EMCal. Its newly utilized photon triggering and the yet to be approved Jet triggering will be mentioned along with a list of related physics topics (with details given in other presentations). Electromagnetic probes / 616 Characterizing cold nuclear matter effects through dielectrons in d+Au collisions at √NN = 200 GeV at PHENIX Jason Kamin1 1 State University of New York at Stony Brook Electron-positron pairs are effective probes for investigating the hot, dense matter created in RHIC collisions because they are carryno color charge and therefore, once created, do not interact strongly with the medium. As a result, they retain characteristics of the full time evolution and dynamics of the system. Among the many features, the low mass region (m<1 GeV/c2) consists primarily of pairs from Dalitz decays of light hadrons and direct decays of vector mesons that can be modified by the medium, while the intermediate (1 147 / 617 Projectile Spectator Detector for the heavy ion program of the NA61/SHINE experiment at the CERN SPS Alexey Kurepin1 225 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 Institute for Nuclear Research of Russian Academy of Siences Study of event-by-event fluctuations as a function of collision energy and size of colliding nuclei to search for the critical point of strongly interacting matter is the main goal of the NA61/SHINE experiment at the CERN SPS. First measurements using secondary beams of light nuclei are planned at the end of this year. Study of fluctuations requires a good control over fluctuations caused by the variation of the number of interacting nucleons. In NA61/SHINE this will be achieved by a very precise measurements of the number of projectile spectators by the very forward hadron calorimeter, the Projectile Spectator detector, developed and constructed for this experiment. The calorimeter consists of 44 modules, each of them being a lead/scintillator sandwich with the sampling ratio satisfying the compensation condition. Light is collected by WLS-fibers embedded in each of 60 scintillator plates of the module. The readout is made by 10 micropixel avalanche photodiodes at rear side in each module. Response of the calorimeter prototype measured during beam tests in the wide energy range, 2A-160A GeV, at the hadron and fragmented beams is presented. 49 / 618 Identified particle flow methods in ALICE at the LHC Christian Ivan1 1 GSI The anisotropic flow of identified particles is an important observable to test the collective behavior of the dense matter created in heavy-ion collisions. We report on the methods used on the first measurements of elliptic and triangular flow for charged pions, kaons, protons, neutral kaons and Lambda in lead-lead collisions at sqrt(sNN )=2.76 TeV measured with the ALICE detector at the LHC. Scalar product and Q-Cumulant techniques were used to estimate the flow for charged (neutral) particles in |eta|<0.8 (0.5). The method presented for Ks and Lambda can be used for any decaying particle. 148 / 619 A Design for a Novel TOF Detector with 10 picosecond Resolu- tion Mickey Chiu1 1 Brookhaven National Lab Recent developments in Time of Flight Detector (TOF) technology have made it possible to achieve timing resolutions of close to 10 ps. Much more development needs to be done, particularly in producing electronics with picosecond resolutions at reasonable cost. We present recent R&D studies at Brookhaven National Lab which study the feasibility of building a detector using micro-channel plate detectors and waveform digitizers, over a relatively small area. With such excellent timing resolution, it would be possible to upgrade PHENIX with a TOF detector covering the full azimuth over moderately forward pseudorapities (0.8 < |η| < 1.5), thus increasing the coverage for PID by a factor of 16. We will also present the wealth of new measurements which would be enabled by such a new detector for PHENIX. 149 / 620 226 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Propose of studying the symmetry energy of asymmetric nuclear matter under super-saturation density at the Cooling Storage Ring at Lanzhou Cheng Li1 1 University of Science and Technology of China Abstract: The Cooling Storage Ring (CSR) at Lanzhou, China is a heavy-ion facility that canacceler- ate nuclei up to 238U with a kinetic projectile energy of several hundred MeV to GeV. By utilizing the CSR heavy-ion beam on an external target, dense QCD matter can be created. The equation of state (EOS) of the strongly coupled matter can be studied via properly chosen physical observables, among which the π-/π+ production ratio probes the symmetry energy of the asymmetrical nuclear matter at high densities. An External Target Experiment (ETE) is currently proposed for thisstudy based on first-stage simulation and experimental work. To provide precise measurements and solid constraint to theory and models, experiment design and systematic requirements must be carefully studied. [References] 1. W.L. Zhan et al., Nucl. Phys. A 805 (2008) 533c 2. X.F. Luo, X. Dong, M. Shao et al., Phys. Rev. C 76, 044902 (2007) 3. Bao-An Li, Lie-Wen Chen, Che Ming Ko, Physics Reports 464 (2008) 113–281 4. Z.G. Xiao, B.A. Li, L.W. Chen, G.C. Yong, and M. Zhang, Phys. Rev. Lett. 102, 062502 (2009) 5. W. Reisdorf et al. (FOPI Collaboration), Nucl. Phys. A 781 (2007) 459 6. Z.Q. Feng, G.M. Jin, Int. J. Mod. Phys. E 19 (2010) 1686 7. W. Trautmann et al., Nucl .Phys. A 834 (2010) 548c 25 / 621 Azimuthal correlation between photon/π0 and charged hadrons with the ALICE experiment Nicolas Arbor1 1 LPSC, UJF Grenoble 1, CNRS/IN2P3, INPG Measurements of the azimuthal correlation between high momentum photons or π0 and charged hadrons allow to investigate parton fragmentation following hard collisions, which will provide new insights on medium effects. We present the experimental analysis which has been applied tothe 2010 proton-proton collisions at √s = 7 TeV by the ALICE collaboration. The technique is based on the detection of both neutral particles (photon or π0) using the EMCal electromagnetic calorimeter, and charged hadrons using the ALICE central tracking system. These proton-proton results should be seen as a reference for heavy ions collisions analysis, and in a broader approach for further gamma-jet studies. 26 / 622 Neutral Pion production in PbPb collisions at sqrt(s_NN)=2.76 TeV measured by ALICE via photon conversions 227 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Daniel Lohner1 1 Ruprecht-Karls-Universitaet Heidelberg The neutral pion yield is measured with ALICE by reconstructing photons via their conversion into e+e- pairs. Transverse momentum spectra are presented for pp and PbPb collisions as well as the resulting nuclear modification factor R_AA. The pi0 yield is studied as a function ofthe emission angle w.r.t. the reaction plane. At high transverse momentum this provides insights into the path-length dependence of jet-quenching. In addition, the reaction plane dependence of the nuclear modification factor R_AA is presented. 27 / 624 Measurement of pi0 production in p+p collisions at sqrt( s ) = 7 TeV with the ALICE EMCal Paraskevi Ganoti1 1 Oak Ridge National Laboratory The measured π0 production spectrum in p+p collisions at 7 TeV (2010 data), where both photons are reconstructed in the ALICE EMCal, will be presented. An accurate measurement of the π 0 produc- tion spectrum requires a thorough understanding of the response of the ALICE EMCal. The details of the analysis are described, including comparisons with Monte Carlo simulations of the EMCal response, in terms of energy non-linearity and resolution, as measured in test beam data. The effect of photon con- versions in the material in front of the EMCal in ALICE on the pT dependence of the π 0 mass and the π 0 reconstruction efficiency will also be discussed. The various fundamental corrections and associated systematic errors, as determined by Monte Carlo simulations will be described and summarized. 28 / 626 Studies of ω(782) → π0γ → 3γ in p+p collisions at √s = 7 TeV with the ALICE electromagnetic calorimeters Renzhuo Wan1 1 IOPP-CCNU, Wuhan, China and IPHC-UDS, Strasbourg, France ALICE electromagnetic calorimeters, PHOS (PHOton Spectrometer) and EMCAL (ElectroMagnetic CALorimeter), have the capability to detect and identify photons over a large pT range. The mea- surement of vector meson ω(782) to π0 γ channel thanks to the calorimeters is interesting both as a test of pQCD and as a probe to explore the properties of hot-dense matter created in heavy-ion colli- sions. Two complementary analysis techniques are explored: one is only based on the three photon invariant mass, while the other takes profit of the cluster shower shapes to constrain the analysis. Here we show the expected pT reach with these techniques. Prospects on the measurement of π0 γ invariant mass studies in pp collisions at √s = 7 TeV will also be presented. 228 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 29 / 627 Measurement of eta meson production in pp collisions at √s = 7 TeV with the ALICE electromagnetic calorimeter Olga Driga1 1 Laboratoire de Physique Subatomique et des Technologies Associees, SUBATECH The measurement of the neutral meson transverse momentum (p_T) spectra in the new energy regime of the LHC is an important input to constrain theoretical models describing hadron pro- duction within the perturbative quantum chromodynamics. Such measurements are the first ones that have been performed by the ALICE electromagnetic calorimeter (EMCal) in proton-proton colli- sions at sqrt(s)=900 GeV, 2.76 TeV and 7 TeV over a wide transverse momentum range at mid-rapidity |y|<0.7. The complete chain of the neutral meson analysis which includes data quality assessment, datacor- rection and Monte Carlo tuning, reconstruction of the raw eta p_T spectrum from invariant mass analysis and efficiency calculations will be presented. Special emphasis on systematic uncertainty evaluation will be made. The direct comparison of the p_T spectra obtained by EMCal, withcom- plimentary measurements by other ALICE detectors allows independent cross-checks of the EMCal results and provides a first test bench for the pQCD predictions at LHC energies in a wide kinematic range. The measured ratio of eta meson and pi0 production will be presented and compared with results obtained at lower energies. 30 / 628 pi0 and eta meson production in pp collisions at 0.9, 2.76 and 7 TeV measured with ALICE PHOS Yuri Kharlov1 1 IHEP The Photon Spectrometer of the ALICE experiment, PHOS, has performed extensive measurements of neutral meson production in proton-proton collisions at the energies of 0.9, 2.76 and 7 TeV. Inclu- sive spectra of pi0 and eta mesons were measured in mid-rapidity in a wide transverse momentum range. Dependence of the pi0 spectrum on event multiplicity has been also studied. Comparison with pQCD calculations allows to constrain the model parameters. Phenomenology of pi0 produc- tion versus collision energy will be discussed. Perspectives on the neutral meson measurements in pp collisions at high pT will be demonstrated. 31 / 629 Correlation Between Mean pT and Charged Particle Multiplicity in pp Collisions at √s = 0.9, 2.76 and 7 TeV with ALICE Philipp Luettig1 1 CERN 229 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / The study of transverse momentum distributions of charged particles in pp collisions attheLHC provides information about both soft and hard contributions to particle production. Charged parti- cle transverse momentum distributions in pp collisions at 0.9, 2.76 and 7 TeV have been measured at mid-rapidity (|eta|< 0.8) by ALICE. We present the energy dependence of the inclusive average transverse momentum 630 Energy density in Pb-Pb Collisions at LHC Oeystein Djuvsland1 1 University of Bergen In ultra-relativistic heavy ion collisions at sufficiently large energy densities, a new state of strongly interacting matter is created, often referred to as the Quark Gluon Plasma (QGP). The produced medium can be attributed a formation time, and a formed energy density canbeesti- mated based on the transverse energy (ET ) produced in these collisions via the Bjorken formula (Bjorken, 1983). Data from Pb-Pb collisions at sqrt{s_NN}=2.76 TeV measured with the ALICE experiment in 2010 has been analyzed to extract dE_T/d_eta for different centrality bins. The measurement has been done with two methods, using the tracking system to obtain the hadronic part and calorimetry for the electromagnetic part of E_T. We will present the status of the measurements, with the main focus on the calorimetry measurement with the ALICE PHOS. Due to its high energy resolution PHOS is well suited for precision measurements starting at low gamma energies. We will also compare to the available theoretical models, which display a rather large variation in their predictions. Results from earlier experiments up to RHIC energies are consistent with a linear increase in E_T with ln(sqrt{s}). Gluon saturation models, which reproduce the charged par- ticle multiplicity well, generally predict a much stronger increase in E_T towards the energies at LHC. The prospects for using E_T measurements to discriminate between theoretical models willbe discussed. 51 / 631 Transverse energy measurements with ALICE in pp and Pb-Pb collisions Christine Nattrass1 1 University of Tennessee/Knoxville The ALICE detector allows precise measurements of the transverse energy in p+p and Pb-Pbcolli- sions at LHC energies. We will discuss studies of the transverse energy in p+p collisions at sqrt{s} = 0.9, 2.76, and 7 TeV and in Pb-Pb collisions at sqrt{s_{NN}} = 2.76 TeV. The ALICE Inner Tracking System (ITS) and the Time Projection Chamber (TPC) are used forprecise measurements of the transverse energy of charged hadrons and the electromagnetic calorimeters 230 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / (PHOS and EMCal) are used for measurements of the transverse energy for electrons, photons, and neutral hadrons which dominantly decay through Dalitz decays. The detector performance will be presented and the measurement technique described indetail. Particular focus will be placed on the hadronic E_T and EMCal measurements, and also on studies with Monte Carlo simulations and assignment of systematic errors for the analyses. 632 Ridge Studies in Pb-Pb Collisions at the LHC based on Number and Transverse Momentum Two-Particle Correlation Functions Claude Andre Pruneau1 1 Wayne State University Observations of a ridge on the near-side, and a dip on the away-side of two-particle correlations measured in central Au + Au collisions have generated considerable interest at RHIC. Are the two phenomena connected? Do they result from jet interactions with the medium, or do they naturally arise from the rapid thermalization and hydrodynamic expansion of collision systems subject to large initial fluctuations? We present measurements, carried with the ALICE detector, of number (R2 ) and transverse momentum (∆pt ∆pt ) correlation functions in Pb + Pb collisions. The two correlation functions are studied as a function of collision centrality for ++, - -, and +- charged particle pairs in various momentum ranges. The like-sign and unlike-sign correlations exhibit a different evolution with collision centrality. We combine these correlations to study charge dependent (CD) and charge independent (CI) correlation functions. We characterize these distributions by studying Fourier decompositions of ∆φ projections of the R2 and ∆pt ∆pt correlation functions for different ranges of ∆η. Of particular interest are the evolution of the ratios of 3rd, and 4th harmonics to the 2nd harmonics with number of participants. We will discuss these results in light of a MC Glauber model of the initial eccentricity of collision nucleon participants. 33 / 633 Three-Particle Jet-Like Correlations in Pb-Pb Collsions at sqrt(s_{NN})=2.76 TeV at ALICE Jason Glyndwr Ulery1 1 Johann-Wolfgang-Goethe Univ. Two-particle correlations at RHIC and SPS in heavy-ion collisions have shown away-side structures that could be explained by conical emission, either from Mach-cone shock waves or Cerenkov gluon radiation, or other physics mechanisms such as path-length dependent energy loss or deflection by radial flow. Three-particle correlations at RHIC showed evidence of conical emission. More recently, triangular flow has been suggested to be present in heavy- ion collisions; it was assumed to be zero in the RHIC and SPS analayses. Triangular flow has also been suggested as a possible source of the structure seen in the correlations at RHIC and SPCs. We study 3-particle correlations at ALICE to look for the presence of conical emission at LHC energies. Backgrounds in this study will include the contributions from the 2nd, 3rd and 4th harmonics of flow. This poster will show the analysis and the results obtained from 2.76 TeV Pb-Pb collision data by the ALICE experiment at the LHC. 231 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 85 / 634 Prompt and detached J/psi production in p–p collisions at Sqrt(s) = 7 TeV with the ALICE detector Carmelo Di Giglio1 1 Universita’ di Bari and INFN sezione di Bari We will discuss the ALICE measurement preparation of the fraction of detached J/ψ (detected via its di-electron decay) coming from beauty hadrons semi-inclusive decays, i.e B → J/ψ + X. The measurement relies on the combined use of the ALICE TPC for tracking and particle identifi- cation via dE/dx, the ITS for tracking and detection of displaced vertices and the TRD for particle identification. Shown results are based on data collected in 2010 in proton-proton collisions at √s = 7 TeV. With increasing statistics following ALICE forthcoming data–taking, the approach adopted will be also crucial for both extracting the prompt J/ψ contribution from the total J/ψ cross–section, and measuring the differential beauty production cross-section, down to very low transverse momen- tum. 34 / 635 Production of Neutral Mesons Identified by ALICE-PHOS in Pb- Pb collisions at sqrt{s_{NN}}=2.76TeV Hisayuki Torii1 1 University of Tokyo The finely segmented structure and small Moliere radius of the ALICE-PHOS detector allowsto separate two photons from a pi^{0} decay at pT=30 GeV/c with an efficiency of about 100%; at even higher pT with smaller efficiency. In this poster, we will present the pi0 production yield measurement with the ALICE-PHOS detector in various centralities in Pb+Pb collisions at sqrt{s_{NN}}=2.76TeV. By comparing the production yield in peripheral collisions to that in pp collisions, we will discuss possible cold nuclear matter effects. The RAA and RCP ratio of pi0 will be presented to be compared with previous resultsatSPS and RHIC. 150 / 636 R&D on MRPC for STAR MTD Yongjie Sun1 1 Dept. of Modern Physics, University of Science and Technology of China A Muon Telescope Detector (MTD) is proposed for the upgrade of the STAR (the Solenoidal Tracker At the RHIC) experiment at RHIC. By the measurement of muons of a few GeV/c, the MTD will allow the detection of 232 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / di-muon pairs from Quark Gluon Plasma (QGP) thermal radiation, quarkonia, and light vector mesons. The correlation of quarks and gluons as QGP resonances, Drell-Yan production, and the measurement of heavy flavor hadrons via semi-leptonic decays into single muons are also possible. These measurements will ad- vance our knowledge of the nuclear matter formed in the relativistic heavy ion collisions at RHIC. MRPC (Multi-gap Resistive Plate Chamber) with long-strip readout will be used as the detector for the MTD with its excellent performance and relatively low cost per channel. This first prototype of LMRPC (Long-strip MRPC) has 10 gas gaps of 250 μm and the signal is read out by six 90 cm long strips of 2.5 cm wide. The test performance with both cosmic ray and test beam shows that the time resolution is around 70 ps, the detection efficiency is higher than 95% and the spatial resolution along strips is less than 1 cm. The“realsize” prototype has 6 gaps of 250 μm and the readout strips are 3.8 cm wide. The cosmic ray test shows the efficiency is higher than 90% and time resolution around 90 ps which is good enough for the MTD requirements. Both the first prototype and “real size” detectors have been installed in STAR and taken data successfully. The mass production of the LMRPC will start soon in this year. Pre equilibrium and initial stage and global collective dynamics / 638 Femtoscopy of PbPb and pp collisions at the LHC with the ALICE experiment [email protected] √ We report on the results of femtoscopic√ analysis of Pb-Pb collisions at sNN = 2.76~TeV with iden- tical pions and pp collisions at s = 0.9, 2.76 and 7~TeV with identical pions and kaons. Detailed femtoscopy studies in heavy-ion collisions at SPS and RHIC have shown that emission region sizes (”HBT radii”) decrease with increasing pair momentum, which is understood as a man- ifestation of the collective behavior of matter. The trend was predicted to persist at the LHC.The data from Pb-Pb collisions confirm the existence of a flowing medium and provide strict constraints on the dynamical models. Similar analysis is carried out for pp collisions for pions and kaons and qualitative similarities to heavy-ion data are seen, especially in collisions producing large number of particles. The observed trends give insight into the soft particle production mechanism inppcol- lisions. 3D radii were also found to universally scale with event multiplicity in heavy-ion collisions. We extend the range of multiplicities both upwards with the Pb-Pb data and downwards with the pp data to test the scaling in new areas. In particular the high multiplicity pp collisions reach particle densities comparable to the ones measured in peripheral Cu-Cu and Au-Au collisions at RHIC. This allows for the first time to directly compare freeze-out sizes for systems with very different initial states. Global collective dynamics / 639 Flow - Theory perspective 233 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Correlations & fluctuations / 640 Common discussion with 4 speakers Correlations & fluctuations / 641 Fluctuations & correlations – TH perspective Correlations & fluctuations / 642 Results from correlation studies in ALICE The talk presents results from hadron correlations in PbPb collisions at 2.76 TeV with ALICE. Un- triggered di-hadron correlations studies are shown which provide a map of the bulk correlation structures in heavy-ion collisions. The long-range correlation region is further studied by triggered correlations which addresses the dependence on trigger and associated pT. The measured correla- tion functions are decomposed with a multi-parameter fit and into Fourier components. The jet yield modification factor I_AA extracted using triggered correlations is presented. 35 / 643 Jet yield enhancement in high-tower trigger events with the AL- ICE Electromagnetic Calorimeter Rongrong Ma1 1 Yale University The ALICE detector carries out comprehensive measurements of high energy nucleus-nucleus colli- sions. Jet reconstruction in ALICE is enabled by combining charged particle measurements in the central tracking system, and neutral particle measurements in the Electromagnetic Calorimeter (EM- Cal). In this poster, we will show the jet yield enhancement using the EMCal high-tower (HT) trigger, compared to minimum bias (MB) trigger, taken in p+p collisions at \sqrt{s}=2.76TeV in 2011. Compar- ison of the two spectra enables determination of the gain in statistics and assessment of HT trigger bias. This work will lead to a measurement of the inclusive differential jet cross-section. Correlations & fluctuations / 644 STAR correlations and fluctuations 234 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Correlations & fluctuations / 645 Common discussion with 4 speakers Closing / 646 Presentation of QM12 Closing / 647 Closing 86 / 648 ALICE vertexing performance and charm reconstruction Xianbao Yuan1 1 University and INFN, Padova, Italy - Institute of Particle Physics, Central China Normal University ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark gluon-plasma in nucleus-nucleus collisions at the LHC. The measurement of open charm and open beauty production allows one to investigate the mechanisms of heavy-quark production, propagation and, at low momenta, hadronisation in the hot and dense medium formed in high-energy nucleus-nucleus collisions. The track impact parameter, defined as the distance of closest approach of a track to the primary(collision or initial) vertex, is the variable allowing to evaluate the displacement of the track. It is a critical variable for the selection of physics signals which are tagged by the secondary vertex with a small displacement from the primary vertex. This is, in particular, the case for the detection of particles with open charm and open beauty,namely D0 (cτ ∼ 123μm) , D+ (cτ ∼ 315μm) and B mesons(cτ ∼ 500μm). The main requirement applied for the selection of such particles is the presence of one or more daughter tracks (decay products) which are displaced from the primary vertex (e.g. for D0 → K− π+ two displaced tracks are required. This poster presents the ALICE track impact parameter resolution for the pp and Pb-Pb collisions, as well as the performance on the exclusive reconstruction of the decay D0 → K− π+. 87 / 649 Preparation for open charm elliptic flow measurement via D-meson decay to hadrons with ALICE Robert Grajcarek1 235 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / 1 University of Heidelberg, Heidelberg, Germany A Large Ion Collider Experiment (ALICE) at the Large Hadron Collider (LHC) has been built in order to identify and characterize the quark gluon plasma (QGP) in high-energy nuclear collisions. As charm quarks are produced at the early stage of the collision, they serve as ideal probes for a QGP. The ALICE detector with its powerful capabilities such as particle identification, vertexing at sub-millimeter precision and tracking in a high multiplicity environment addresses the charm sector in nuclear collisions. It is still an open question whether charm quarks take part in the collective motion of the expanding fireball in ultrarelativistic heavy ion collisions. The determination of the anisotropy parameter v2 of the D-mesons D+, D0 and D∗+ will providea decisive answer. We report on the current status of the development of the tools for the D-meson v2-measurement at ALICE for the three charmed mesons in various hadronic decay channels. We will show performance plots obtained with these tools from the 2010 lead-lead run at √s_NN = 2.76 TeV and will give an outlook for the upcoming high statistics lead-lead run at the end of this year. 650 Probing the gluonic structure of matter at a future Electron-Ion Collider The probing of nuclei and nucleons via deep-inelastic and diffractive processes in the high-energy (low-x) regime will open a new precision window for the investigation of the gluonic structure of matter. Studies of e+p collisions at HERA and especially d+Au collisions at RHIC have found tantalizing hints of saturated gluon densities, a phenomenon with substantial impact on the physics of heavy- ion collisions. Unveiling the collective behavior of densely packed gluons under conditions where their self-interactions dominate will require an Electron-Ion Collider (EIC): a new facility with capa- bilities well beyond those of any existing accelerator. Such a collider could be sited either at BNL or JLAB. In my talk I will outline the compelling physics case for e+A collisions with a focus on the oppor- tunities for small-x physics. I will discuss the related key measurements and give a brief status of machine concepts, detector design, and timeline. 651 eA collisions at the Large Hadron-electron Collider I will show the possibilities for electron-ion studies offered by the proposed electron-hadron col- lider at CERN, the Large Hadron-electron Collider [1]. After a short introduction on open problems at small x, I will briefly present the machine and detector. Then I will focus on small-x aspectsin electron-nucleus collisions, first on inclusive measurements and the determination of nuclear par- ton densities, and then on diffraction. I will finish by discussing some opportunities for finalstate studies. [1] M. Klein et al., Prospects for a Large Hadron Electron Collider (LHeC) at the LHC, EPAC’08, 11th European Parti cle Accelerator Conference, 23- 27 June 2008, Genoa, Italy; http://cern.ch/lhec. 236 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / IAC / 652 Proposal for QM13/14 in Japan [email protected], [email protected] IAC / 653 Preparation of QM2012 at Washington [email protected], [email protected], [email protected] IAC / 654 Proposal for QM13/14 in Darmstadt Electromagnetic probes / 655 Leptonic observables in sqrt(s_NN)=2.76 TeV PbPb collisions mea- sured with the ATLAS detector at the LHC A broad program of measurements using heavy ion collisions is underway in ATLAS, with the aim of studying the properties of QCD matter at high temperatures and densities. Leptonic observables are essential tools for the study of heavy ion collisions since leptons do not interact strongly and thus pass through the strongly-coupled medium unaffected. The centrality dependence of J/psi and Z yields, observed through their di-muon channel, are important measurements both for assessing modifications of particle production as well as probing particular regions of the nuclear PDFs.W boson measurements are also possible using single leptons, and provide another handle on the initial state. This talk describes measurements performed using up to 9 µb-1 of lead-lead collision data provided at a nucleon-nucleon center-of-mass energy of 2.76 GeV by the Large Hadron Collider and collected by the ATLAS Detector during November and December 2010 IAC / 656 Proposal for QM13/14 in Bologna 50 / 658 237 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Charged-particle multiplicities in proton–proton collisions at √s = 0.9 TeV and 7 TeV, with the ALICE Forward Multiplicity Detec- tor at LHC 659 Charged pion spectra at high pT measured via dE/dx with the AL- ICE TPC Peter Christiansen1 1 Lund University The TPC is the main tracking detector in the central barrel(|η| ≤ 1) of the ALICE experiment. In ad- dition to tracking it provides particle identification through the measurement of the specific energy loss, dE/dx, which depends only on βγ = p/m. At low momentum, p<1GeV/c, pions, kaons, and protons, can be cleanly separated in different momentum intervals. At high momentum, p>3GeV/c, the yield of pions, kaons, and protons can be extracted statistically on the relativistic rise. In this poster I will show results from pp @ 2.76 TeV and Pb-Pb @ 2.76 TeV/nucleon for 3.0 11 / 660 Charged pion spectra at high pT measured via dE/dx with the AL- ICE TPC Peter Christiansen1 1 Lund University The TPC is the main tracking detector in the central barrel(|η| ≤ 1) of the ALICE experiment. In ad- dition to tracking it provides particle identification through the measurement of the specific energy loss, dE/dx, which depends only on βγ = p/m. At low momentum, p<1GeV/c, pions, kaons, and protons, can be cleanly separated in different momentum intervals. At high momentum, p>3GeV/c, the yield of pions, kaons, and protons can be extracted statistically on the relativistic rise. In this poster I will show results from pp @ 2.76 TeV and Pb-Pb @ 2.76 TeV/nucleon for 3.0 IAC / 661 Proposal for a QM in Brazil 238 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / IAC / 662 QM2011 Flash talks / 663 First B→J/ψ measurement in PbPb collisions at 2.76 TeV with the CMS detector Flash talks / 664 First measurement of Upsilon suppression 665 pending Yvonne Pachmayer1 1 Univ. Heidelberg Flash talks / 666 Measurement of the Nuclear Modification Factor of Electrons from Heavy Flavour Decays at Mid-Rapidity in Pb-Pb Collisions at 2.76 TeV with ALICE Flash talks / 667 Probing nuclear parton densities and parton energy loss processes through photon + heavy-quark jet production in p-A and A-A col- lisions Flash talks / 668 239 QM 2011 - XXII International Conference on Ultrarelativistic Nucleus- … / Dimuon radiation at the CERN SPS within a hybrid evolution model Flash talks / 669 Local Parity Violation or Local Charge Conservation/Flow? Flash talks / 670 Production of (anti)nuclei in pp and PbPb collisions with ALICE at the LHC Flash talks / 671 Continuous Time Monte Carlo for QCD in the Strong Coupling Limit 240