PoS(EPS-HEP 2009)044 − γ http://pos.sissa.it/ 5 TeV allowing high . bosons. The Compact 5 0 redistribution of particles = Z T p NN S √ family in the central rapidity region ϒ jets. The muon chambers combined b and the ψ / J , jets, photons, as well as 0 T Z p , high- ϒ and b for the CMS Collaboration ∗ ivan.amos.cali@.ch within the jet. The large CMS acceptance will allow detailed studies of jet structure in rare Muon Solenoid (CMS) detectorscollisions. will allow The a CMS wide datatrigger range system, acquisition of is system, uniquely unique qualified with measurements forThe efficient its in excellent triggering reliance calorimeters in nuclear combined high-multiplicity on with heavy tracking a ion will events. medium multipurpose, allow effects detailed on high-level studies the of jet jets, fragmentation function particularly and the energy and Speaker. statistics studies of thewith dense an partonic emphasis system on with the hard probes: heavy and quarkonia The Large Collider at CERN will collide lead ions at with tracking will study production of the of the collision. Inmultiplicity, addition energy to flow and the azimuthal detailed asymmetry event-by-event. studies of hard probes, CMS will measure charged and Z-jet events. The high resolution tracker will tag ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c ⃝ The 2009 Europhysics Conference on HighJuly Energy 16 Physics, - 22 2009 Krakow, Poland Ivan Amos Cali Massachusetts Institute of Technology E-mail: CMS Experiment at LHC: Detector StatusPhysics Capabilities and in Heavy Ion Collisions PoS(EPS-HEP 2009)044 . c / 3. . 3 m. (left) 8 1 ∼ GeV jets and | ≥ T η | E 3 and the very 5 to 50 . < | pixels) followed by η | 2 m 6, and yet another zero , heavy-quarks, . µ 6 T p < 150 175 at forward rapidities. A | region from 0 . × 0 η T | ]. The LHC plans to collide Pb p × 4, with detection planes made of 1 < . 4. It consists of thirteen layers of . 2 2 2 . 175 . < < | | η 2. The ECal has an energy resolution of | η . | 5 < | values up to 1 TeV/c. η 2 | T ). The tracking system allows track reconstruction p < ] is a general purpose detector designed primarily to m accuracy and it gives the possibility to clear resolving 2 µ m µ 180 15 ÷ ∼ 300, compared to the minimum bias (MB) condition. Fig. 087 at central rapidities and 0 ∼ . 0 × 087 . 5 TeV which is 28 times higher than the highest energy available at RHIC. . 0 5 = = δϕ NN bosons). In this paper the Compact Muons Solenoid (CMS) detector capabilities for s × ± family. √ − W δη ϒ The (CMS) [ The motivation of ongoing relativistic heavy-ion collision experiments is to understand the and 0 degree calorimeter (ZDC) located as farThe as unique 140 CMS m trigger from the architecture interactionHigh only point employs Level the two Trigger region trigger (HLT). levels: Thecal the Level-1 data Level-1 is from trigger implemented the and using calorimeter the In custom and muon electronics order systems and to to it fully make uses exploita electron/photon, lo- the large jets cluster detector and of muon capabilities triggers. workstations forevent running without rare offline filtering hard analysis at probes trigger the athard algorithms probes first the on by level. LHC, every a the single factor This HLT of Pb+Pb shows results uses 20 the gain in in significant statistics enhancements with respect of to various minbias rare writing to tape as achieved for high- nuclei at search for Higgs boson in proton-protonis collisions an at LHC. excellent However device this for large the acceptanceThe study detector basic of element hard and of soft CMS probesThe is in tracking a both system 13m-long, pp high covers and AA field the collisions. (4T) pseudorapidity solenoid region with internal radius of The collisions should produce copious hard probes such as jets, high- 2. The CMS Detector and Heavy Ion Program and momentum estimation with resolution better than 2% in the bulk properties of high energyChromo Dynamics density (QCD). matter and theThe theory experiments at of the the Relativistic strong Heavytant Ion interaction, signatures Collider Quantum for (RHIC) the facility Quark- have found Plasma several (QGP) impor- formation [ CMS Experiment at LHC:Ivan Detector Amos Status Cali and Physics Capabilities in Heavy Ion Collisions 1. Introduction quarkonia and large yields of theZ weakly interacting perturbative probes (direct photons,heavy-ion dileptons, physics at LHC are summarized with an emphasis on the early measurements. ten microstrip layers (strips pitch 80 It provides the vertex position with forward (HF) calorimeters span the region 3 quartz-fibre calorimeter named CASTOR covers the region 5 of the The muon chambers cover the pseudorapidity window The electromagnetic (ECal) and hadron (HCal) calorimeters cover the range better than 0.5% above 100ularity GeV. The calorimeter cells are grouped in projective towers, of gran- silicon detectors. The first three layers are pixel detectors (66 M 100 three technologies: Drift Tubes (DTs), Cathode Stripbers Chambers (RPCs). (CSCs), Matching and the Resistive muons Plate to Cham- themomentum tracks resolution measured in between the 1 silicon and tracker results 5 in %, a for transverse PoS(EPS-HEP 2009)044 ≃ p for protons. are an important tool to c parameter obtained by the / T in differential form will be p 2 2 v v GeV 2 ≃ p both by reconstructing the reaction plane and 2 3 v ] predicts a significant reduction of the number of spectra for charged hadrons expected with the CMS 1 T spectra for charged hadrons expected with the CMS HLT at p T (left). p 2 for pions and kaons and up to , is the strength of the second harmonic of the azimuthal distribution 2 c v / GeV 1 ≃ p (right) shows the invariant 1 Hadron Spectra and Elliptic Flow , and the momentum of track. Inclusive hadron spectra can be measured from up to T (Left) The gain in statistics with respect to minbias writing to tape as achieved with HLT for c dx p / / jets and dimuons. (Right) Invariant T dE E Measurements of hadron momentum spectra and ratios at low The charged particle multiplicity per unit of rapidity at mid-rapidity is related to the entropy MeV various Pb+Pb centralities. 4. Low- density in the collisionsthe and idea fixes of the Color global Glass properties Condensate of (CGC) the [ produced medium. For example, high- 3. Charged Hadron Multiplicity determine the amount ofsystem collective at freeze-out. radial The flow CMS tracking and algorithmsloss, allow the to identify thermal particles by and comparing300 chemical energy conditions of the Figure 1: produced hadrons at the LHC duedistribution to functions the (PDFs). reduced initial CMS numberparticle is of multiplicities planning scattering by to centers tree make in methods: a thepixels using 1) parton first a tracklets day dE/dx with measurement cut a and of vertex 3) the constraint reconstructed charged tracks. 2) hit counting in the CMS Experiment at LHC:Ivan Detector Amos Status Cali and Physics Capabilities in Heavy Ion Collisions dimuons. Fig. HLT at various Pb+Pb centralities. The elliptic flow parameter, of hadrons with respect to the reaction plane. The measurement of by using multiparticle correlators or cummulants. The differential primarily important to learn the collectiveand properties, the such as equation-of-state. the viscosity, of CMS the will fluid-like measure matter event-plane method is displayed in Fig. PoS(EPS-HEP 2009)044 and γ cuts on , the so-called T T p E reach of the charged T shows the ratio of the p 2 coverage. It has been demon- π hadron suppression is due to the and the full reconstruction is pos- T p 100 % for both) and a good energy GeV ∼ is not influenced by the final-state inter- 30 γ ∼ 3 rad in addition to the low- T E < ). (Right) Ratio of the reconstructed quenched FF to 4 ]. The right side of Fig. jet 3 − [ ). TeV γ 5 ϕ γ T . p 5 ∆ / γ = T E NN s ), since the prompt channel is that we can infer the initial parton energy from the = ln( √ parameter obtained by the event-plane method. The open circles rep- γ T events and extracting the parton fragmentation function (FF). The 2 E ξ . The CMS can also investigate the jet quenching effect with the jet v c / ≈ jet − γ − jet simulation study has shown that the FF can be measured within 10 % T GeV γ E with good efficiency and purity ( ( jet γ 300 − ∼ GeV γ triggering capability, the CMS can significantly extend the 75 T p > T (Left) The differential ] that the CMS can reconstruct jets in a messy environment, generated by Pb+Pb col- E 2 The energy loss mechanism of fast partons in the strongly interacting medium can be studied A major discovery at the RHIC is the hadron suppression at relatively high- the unquenched one as function of Figure 2: resent the simulated datastructed with ones the (Pb+Pb HYDJET collisions event at generator, and ˛A the closed squares represent the recon- sible for resolution (< 15 %). further by analyzing the actions. The full jet as well as the special isolation cuts on 6. Fragmentation Function lisions, after the subtractiondistinction of of the jets underlying above soft the background background begins on at an event-by-event basis. The advantage of utilizing the CMS Experiment at LHC:Ivan Detector Amos Status Cali and Physics Capabilities in Heavy Ion Collisions 5. Nuclear Modification Factor strated [ reconstructed quenched FF to the unquenchedof one, which the allows fragmentation us function to by investigate the any medium. modification jet quenching effect. We presently understand that the high- final state effect caused bystrongly interacting the medium. produced dense matter:Thanks to the the enhanced energy hard cross loss sectionsand at of the LHC partons energy, high- the traversing excellent performance the of thehadron tracker, spectra to fully reconstructed jets, measured by its calorimeters with almost 4 by constraining the away-side jet axis by transverse energy of PoS(EPS-HEP 2009)044 90% ∼ ]. 8 (Pb+Pb . 4 0 [ < ψ | / η , and it worsens J | 2 c / . As a consequence, π 2500 in state can be measured MeV = ϒ 0 = 4. . η 80% and the purity is | 2 4. In addition, the simulation . η 2 ∼ d < / | < η | pairs and secondary s is about 54 | η ϒ | dNch for µµ 2 c (right) regions. / ϒ MeV 5 (left) and the ψ should be observed with high statistics under the conditions of / J 0 8. The mass resolution of . Z 0 < | ) and η s | ) near the ϒ , ′ with the reconstruction efficiency between 15 and 40 %, depending on the TeV ψ mass resolution is about 35 c 5 , . if we include the endcap detectors for / ψ 5 ψ 2 / c / = J / J GeV 0 NN s ∼ √ MeV mass regions in T Invariant mass spectra of opposite sign muon pairs with ϒ p shows the reconstructed invariant mass distributions of opposite sign muon pairs near the 3 Karsch F, Kharzeev D, and H. Satz 2006 Phys. Lett. B 637 75. Chen Y et al. 2008 CMS CR-2008/055. For example: Adcox D et al.(BRAHMS),Quark-gluon [PHENIX plasma Collaboration] and 2005 color Nucl. glass Phys. condensateBRAHMS A at experiment, 757 RHIC? Nucl. 184; The Phys. I. perspective A Arsene from 757, et the (2005) al 1. CMS Collaboration, The CMS experiment atCollaboration, the CMS CERN TDR LHC, Addendum: 2008 High-Density JINST QCDPhys. 3 with 34 S08004; Heavy (2007) CMS Ions, 2307. J. Phys. G: Nucl. Part. and In summary, the CMS detector is equipped with high-granularity high-resolution Si pixels Quarkonia ( ψ / [3] [4] [1] [2] the CMS detector isIn an particular, excellent the system CMS notacceptance has and only a the for dedicated strong p HLT.We have advantageof shown + almost measuring that all p, the various physics CMS but topics hard can in also probes perform both for soft the due and detailed heavy-ion to hard studies collisions. sectorsReferences the in heavy-ion large collisions. and trackers, calorimeters, and muon detection systems, covering almost 4 8. Summary Figure 3: collisions at LHC. Large cross-section for heavy quarkenergy (b, loss c) of production partons basing allows evaluation on of the medium-induced spectra of large mass J CMS Experiment at LHC:Ivan Detector Amos Status Cali and Physics Capabilities in Heavy Ion Collisions 7. Quarkonia and Heavy Quarks Fig. study has shown that the efficiency for the muon pair detection is even for the mostdown central to Pb+Pb collisions inmomentum. The the barrel region. The to about 90