HighlightsHighlights fromfrom thethe STARSTAR experimentexperiment
Hanna Zbroszczyk for the STAR Collaboration
Faculty of Physics, Warsaw University of Technology
MESON 2018, Kraków, 9th June 2018 1 IntroductionIntroduction
2 RRelativisticelativistic HHeavyeavy IIonon CColliderollider (RHIC)(RHIC) BrookhavenBrookhaven NationalNational LaboratoryLaboratory (BNL),(BNL), NewNew YorkYork
PHOBOS BRAHMS PHENIX RHIC STAR
AGS
TANDEMS
• 2 concentric rings of 1740 superconducting magnets 3 • 3.8 km circumference TheThe SSolenoidalolenoidal TTrackerracker AAtt RRHICHIC
.1
4 IntroductionIntroduction RHIC Top Energy p+p, p+Al, p+Au, d+Au, 3He+Au, Cu+Cu, Cu+Au, Ru+Ru, Zr+Zr, Au+Au, U+U QCD at high energy density/temperature Properties of QGP, EoS
Beam Energy Scan Au+Au 7.7-62 GeV QCD phase transition Search for critical point Turn-off of QGP signatures
Fixed-Target Program Au+Au =3.0-7.7 GeV High baryon density regime with 420-720 MeV 5 IntroductionIntroduction 1. Open heavy flavor - D0 v , D0 R and R , 1 AA CP ΛC 2. Quarkonium – R Υ AA
3. Jet modification and high-pT hadrons - di-jet imbalance, di-hadron correlation
4. Chirality, vorticity and polarization effects - Λ polarization, Φ polarization, CME, CMW
5. Initial state physics and approach to equilibrium - v and v fluctuations 2 3 6. Collectivity in small systems - v in p+Au and d+Au 2 7. Collective dynamics - longitudinal decorrelation, identified particle v 1 8. High baryon density and astrophysics - v from fixed target 1
9. Correlations and fluctuations – femtoscopy 10. Phase diagram and search for the critical point - net Λ and off-diagonal cumulants 11. Thermodynamics and hadron chemistry - triton, hypertriton mass
6 12. Upgrades - BES-II and forward upgrades IntroductionIntroduction 1. Open heavy flavor - D0 v , D0 R and R , 1 AA CP ΛC 2. Quarkonium – R Υ AA
3. Jet modification and high-pT hadrons - di-jet imbalance, di-hadron correlation
4. Chirality, vorticity and polarization effects - Λ polarization, Φ polarization, CME, CMW
2. Initial state physics and approach to equilibrium - v and v fluctuations 2 3 3. Collectivity in small systems - v in p+Au and d+Au 2 7. Collective dynamics - longitudinal decorrelation, identified particle v 1 4. High baryon density and astrophysics - v from fixed target 1
5. Correlations and fluctuations – femtoscopy 10. Phase diagram and search for the critical point - net Λ and off-diagonal cumulants 6. Thermodynamics and hadron chemistry - triton, hypertriton mass
7 7. Upgrades - BES-II and forward upgrades (as summary) ResultsResults
8 1)1) DD0 –– OpenOpen heavyheavy flavorflavor
First evidence of non-zero D0 v is measured. 1 Probe the initial tilt of the source and the initial EM field 9 2)2) InitialInitial statestate physicsphysics
Q-cumulant method (traditional)
Φ - azimuthal angle Two-subevent method
Sensitive to flow fluctuations10 11 2)2) InitialInitial statestate physicsphysics
Strong dependence of v {k} on collision 2 energy.
Weak dependence of v {4}/v {2} on collision 2 2 centrality
11 2)2) InitialInitial statestate physicsphysics
Strong dependence of v {2} and v {4} on 2 2 collision centrality.
Weak dependence of v {2}/v {4} on collision 2 2 centrality
12 2)2) InitialInitial statestate physicsphysics
Weak dependence of v {2}/v {4} on transverse momentum 2 2
13 2)2) InitialInitial statestate physicsphysics
Significant dependence of v {2}, v {4} 2 2 and v {2}/v {4} on
14 2)2) InitialInitial statestate physicsphysics
Anisotropic flow magnitude is sensitive to: - initial-state spatial anisotropy - flow fluctuations and correlations - viscous attenuation ( ∝ η/s (T) )
Weak dependence of v {2}/ {2} 2 ε2 on collision centrality among different systems.
Are dynamical final-state fluctuations significantly less than the initial-state fluctuations? 15 2)2) InitialInitial statestate physicsphysics
Strong dependence of v {2}, v {4} on collision centrality, 2 2 collision energy, transverse momentum
Weak dependence of v {4}/v {2} and v {2}/ {2} (elliptic flow 2 2 2 ε2 fluctuations) on the size of colliding system and: collision centrality, collision energy, transverse momentum
Flow flucuations are dominated by the fluctuations of the initial state eccentricity
Similar viscous coefficient for different colliding systems
16 3)3) SmallSmall systemssystems
Near-side ridge observed in High Multiplicity (HM) of d+Au collisions
17 3)3) SmallSmall systemssystems
Low multiplicity subtraction scaled by short-range near-side (|Δη|<0.5) jet yield
Short-range near-side jet modification = long-range away-side jet modification Template fit
A new method by ATLAS Collaboration away-side jet shape can be measured in Low Multiplicity (LM) events scaled by ”F” parameter (due to jet modification)
18 3)3) SmallSmall systemssystems v without subtraction is larger than that 2 with subtraction for both methods.
The subtraction of non-flow contributions are very important for STAR results are comparable with PHENIX results.
At lowet p v from Low Multiplicity T 2 subtraction is 35% lower than from template fit
At intermediate p they agree with each T other
STAR results are comparable with PHENIX ones.
19 3)3) SmallSmall systemssystems v in p+Au collisions without 2 subtraction is larger than v in 2 d+Au collisions that with subtraction for both methods. v in p+Au collisions from Low 2 Multiplicity subtraction is lower than from template fit.
STAR results are comparable with PHENIX results, except at high pT. The STAR data is clearly lower than PHENIX for p >1.5 GeV/c T
20 3)3) SmallSmall systemssystems
Large difference between subtraction method and template fit v from subtraction method is negative at lower collision energies 2 (different kinematics between near-side and away-side jet-like correlations?) v from template fit increases with collision centrality 21 2 c 3)3) SmallSmall systemssystems v becomes negative at 2 high transverse momentum in d+Au collisions at low collision energy
The correlation from away-side jet is stronger at high transverse momentum
22 3)3) SmallSmall systemssystems
Large difference between v from two methods has been 2 observed at low energy → large uncertainties in the non-flow subtraction in small systems.
We do see similar v between p+Au and d+Au collisions for 2 same multiplicity → v is not only driven by initial geometry. 2
The integral v extracted by a template fit shows an universal 2 trend as a function of
23 4)4) FixedFixed targettarget modemode
BES goals: Collider mode is unusable - Search for 1st order phase for s <7.7 GeV ⎷ NN transition - Search for existance of the Fix target mode is able to Critical Point cover ⎷s from 3.0 GeV to - Search for turn-off QGP NN 7.7 GeV signatures 24 4)4) FixedFixed targettarget modemode
(1)
Detector’s scheme (2a) (2b)
Spectra corrections:
Detector efficiency Detector acceptance (each rapidity window) Energy loss
25 4)4) FixedFixed targettarget modemode
π- spectra are consistent with AGS results. 26 4)4) FixedFixed targettarget modemode
Directed flow for pions and protons with fit describing mid- rapidity region. 27 Directed flow of protons agrees with AGS results. 4)4) FixedFixed targettarget modemode
Directed flow for and K0 particles and their fits describing mid-rapidity Λ S region.
28 4)4) FixedFixed targettarget modemode
Directed flow for identified particles agrees with AGS results.
29 4)4) FixedFixed targettarget modemode
HBT radii for pions are consistent with AGS results. 30 4)4) FixedFixed targettarget modemode
- STAR is ready to operate with the Fixed Target mode - Spectra and particle yields agree with AGS results - Proton directed flow and elliptic flow (v and v ) agree with AGS 1 2 results - HBT radii agree with AGS results
High-baryon density regime will be accessible with the Fix Target mode in STAR!
31 5)5) FemtoscopyFemtoscopy
Single- and two- particle distributions
dN 4 S(x,p) – emission function: the distribution P1( p)=E 3 =∫ d x S(x , p) d p of source density probability of finding particle with x and p
dN 4 4 P2( p1 , p2)=E1 E 2 3 3 =∫ d x1 S (x1 , p1)d x2 S (x2 , p2)Φ(x2, p2∣x1, p1) d p1 d p2
The correlation function
P2( p1, p2) C( p1 , p2)= P1( p1)P1( p2) 32 Pair Rest Frame reference 5)5) FemtoscopyFemtoscopy UrQMD Au+Au
Identical baryon- baryon
- Quantum Statistics- QS
- Final State Interactions- FSI - Coulomb 0.1 0.05 k* [GeV/c] - Strong
Non-identical baryon- (anti)baryon
- Final State Interactions- FSI - Coulomb UrQMD - Strong Au+Au 33 5)5) FemtoscopyFemtoscopy
proton-proton @39 GeV antiproton-antiproton @39 GeV
STAR Preliminary STAR Preliminary
QM 2018 QM 2018
No significant difference between proton-proton and antiproton-antiproton correlation functions
34 5)5) FemtoscopyFemtoscopy
Radii from proton-proton and STAR Preliminary antiproton-antiproton systems QM 2018 differ from those from proton- antiprootn system → Residual Correlations. Residual feed-down correction needs to be applied.
proton-proton @39 GeV proton-antiproton @39 GeV
STAR Preliminary
QM 2018
35 5)5) FemtoscopyFemtoscopy
proton-proton, centrality 0-10% proton-antiproton, centrality 0-10%
QM 2018 QM 2018
Energy dependence more significant for proton-proton than for proton-antiproton system.
36 38 5)5) FemtoscopyFemtoscopy
STAR Preliminary
0-10%
QM 2018 10-30% 30-70%
Feed-down correction may decrease significance of centrality dependence. 37 5)5) FemtoscopyFemtoscopy
- Clear centrality dependence of source size at BES energies - Visible energy dependence of source size at BES energies - No visible difference between proton-proton and antiproton-antiproton correlation functions at √s = 39 GeV NN - Correlation functions contaminated by residual correlations – residual correction required
403 8 6)6) HypertritonHypertriton
Hyperon-Nucleon: - play an important role in neutron star and QCD theory
- measurements of masses of hypertriton and anti-hypertriton provide insight into H-N interactions and the CPT symmetry
- measurements sensitive to the temperature and nucleon phase-space of the system freeze- out.
39 41 6)6) HypertritonHypertriton
40 6)6) HypertritonHypertriton
41 6)6) HypertritonHypertriton
Worldwide binding energy of 3 H of experimental Λ measurements.
Measurements of the mass- over-charge ratio differences between light nuclei and anti- nuclei.
42 ConclusionsConclusions && SummarySummary
43 SummarySummary 1. Open heavy flavor - D0 v , D0 R and R , 1 AA CP ΛC 2. Quarkonium – R Υ AA
3. Jet modification and high-pT hadrons - di-jet imbalance, di-hadron correlation
4. Chirality, vorticity and polarization effects - Λ polarization, Φ polarization, CME, CMW
5. Initial state physics and approach to equilibrium - v and v fluctuations 2 3 6. Collectivity in small systems - v in p+Au and d+Au 2 7. Collective dynamics - longitudinal decorrelation, identified particle v 1 8. High baryon density and astrophysics - v from fixed target 1
9. Correlations and fluctuations – femtoscopy 10. Phase diagram and search for the critical point - net Λ and off-diagonal cumulants 11. Thermodynamics and hadron chemistry - triton, hypertriton mass
44 12. Upgrades - BES-II and forward upgrades UpgradesUpgrades
STAR
45 UpgradesUpgrades
46 ThankThank you!you!
Grazyna Odyniec/LBNL 47 6)6) HipertritonHipertriton
48 6)6) HipertritonHipertriton
49 6)6) HipertritonHipertriton
50 6)6) HipertritonHipertriton
51