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High-Energy Nuclear Collisions and the QCD Phase Structure Nu Xu Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley, USA. The QCD Phase Diagram and High-Energy Nuclear Collisions. T ini , T C LHC, RHIC. T E RHIC , SPS , FAIR. Phase boundary

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  1. High-Energy Nuclear Collisions and the QCD Phase Structure Nu Xu Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley, USA

  2. The QCD Phase Diagram and High-Energy Nuclear Collisions Tini, TC LHC, RHIC TERHIC, SPS, FAIR Phase boundary RHIC,FAIR, NICA 3 2 1 quark-gluon plasma Early Universe 1 2 3 TE Critical Point? Temperature hadron gas CSC nuclei Baryon Chemical Potential

  3. Quantum Chromodynamics 1) Quantum Chromodynamics (QCD) is the established theory of strongly interacting matter. 2) Gluons hold quarks together to from hadrons. 3) Gluons and quarks, or partons, typically exist in a color singlet state: confinement. Little is known about the structure of the matter. meson baryon

  4. Phase diagram: A map shows that, at given degrees of freedom, how matter organize itself under external conditions. The QCDPhase diagram: structure of matter with quark- and gluon-degrees (color degrees) of freedom. Phase Diagram: Water

  5. QCD Phase Diagram (1953) RHIC Neutron stars Neutron stars Neutron stars E. Fermi: “Notes on Thermodynamics and Statistics ” (1953)

  6. QCD Phase Diagram 1983 (1, 2, 5-10)ρ0 1983 US Long Range Plan - by Gordon Baym TC~200 MeV (1, 2, 5-10)*ρ0

  7. QCD Phase Diagram (2009) 1983 US Long Range Plan - by Gordon Baym nucl-th: 0907.4489, NPA830,709(09)L. McLerran nucl-th 0911.4806:A. Andronic, D. Blaschke, P. Braun-Munzinger, J. Cleymans, K. Fukushima, L.D. McLerran, H. Oeschler, R.D. Pisarski, K. Redlich, C. Sasaki,H. Satz, and J. Stache Systematic experimental measurements (Ebeam, A) : extract numbers that may be related to the QCD phase diagram!

  8. Outline • Introduction • STAR experiment and physics program • Observables, and recent results • - Three examples: (i) v2; (ii) S, K; (iii) di-elelctron • - Many more will be discussed during the workshop • Summary

  9. STAR Detectors Fast and Full azimuthal particle identification EMC+EEMC+FMS (-1 ≤  ≤ 4) TPC TOF DAQ1000 HFT 2013 FGT 2011 BNL PAC, 21 - 22, 2010 MTD 2013

  10. Particle Identification at STAR TPC ToF TPC STAR TPC K pd π e, μ STAR ToF Log10(p) STAR MTD STAR HFT STAR EMC Neutral particles Strange Jets Heavy Quark hyperons Hadrons Multiple-fold correlations among the identified particles!

  11. TOF Performance √sNN = 39 GeV Au + Au Collisions TPCTPC+ToF

  12. PID: 7.7, 39, 200 GeV (p±, K±, p) Au+Au at 7.7 GeV Au+Au at 39 GeV Au+Au at 200 GeV

  13. 1) At 200 GeV top energy - Study medium properties, EoS - pQCD in hot and dense medium 2) RHIC beam energy scan (BES) - Search for the QCD critical point - Chiral symmetry restoration STAR Physics Focus Forward program - Study low-x properties, initial condition, search for CGC - Study elastic and inelastic processes in pp2pp Polarized p+p program - Study proton intrinsic properties

  14. The QCD Critical Point - LGT prediction on the transition temperature TC is robust. - LGT calculation, universality, and models hinted the existence of the critical point on the QCD phase diagram* at finite baryon chemical potential. - Experimental evidence for either the critical point or 1st order transition is important for our knowledge of the QCD phase diagram*. * Thermalization has been assumed M. Stephanov, K. Rajagopal, and E. Shuryak, PRL 81, 4816(98); K. Rajagopal, PR D61, 105017 (00) http://www.er.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf

  15. Maximum Baryon Density The maximum baryon density at freeze-out: √sNN ~ 8 GeV

  16. Example I: Partonic Collectivity

  17. Anisotropy Parameter v2 coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, EoS, degrees of freedom

  18. Collectivity, De-confinement at RHIC - v2 of light hadrons and multi-strange hadrons - scaling by the number of quarks At RHIC: nq-scaling novel hadronization process • Partonic flow • De-confinement • PHENIX: PRL91, 182301(03) • STAR: PRL92, 052302(04), 95, 122301(05) • nucl-ex/0405022, QM05 • S. Voloshin, NPA715, 379(03) • Models: Greco et al, PRC68, 034904(03) • Chen, Ko, nucl-th/0602025 • Nonaka et al. PLB583, 73(04) • X. Dong, et al., Phys. Lett. B597, 328(04). • …. i ii

  19. System Size Driven Collectivity STAR: PRC81,44902(10) Collectivity: Driven by number of participants More Analysis: How and when local equilibrium reached

  20. Partonic Collectivity at RHIC PHENIX: nucl-ex/0604011 STAR: preliminary QM09: arXiv 0907.2265 Low pT(≤ 2 GeV/c): hydrodynamic mass ordering High pT (> 2 GeV/c): number of quarks ordering s-quark hadron: smaller interaction strength in hadronic medium light- and s-quark hadrons: similar v2 pattern => Partonic Collectivity at RHIC !

  21. Thenq-scaling in Hadron v2 Scaling for all hadrons up to pT ≥ 3 GeV/c in case of partonic scatterings and coalescence. No scaling in case of hadronic scatterings.

  22. Observable: Quark Scaling  • m ~ mp ~ 1 GeV • ss not K+K- • h<< p,  • In the hadronic case: • No number of quark scaling • Very small value of v2 !

  23. Example II:High Order Correlation Functions

  24. Correlations, Susceptibilities, Kurtosis Higher order correlations are correspond to higher power of the correlation length of the system: more sensitive to critical phenomena. M. A. Stephanov, PRL. 102, 032301 (09) • Skewness: Symmetry of the correlation function. • Kurtosis: Peaknessof the correlation function. Connection to thermodynamics, X. S & Kobservables: total charge, total protons, net-p, net-Q R.V. Gavai and S. Gupta: 1001.2796. F. Karsch and K. Redlich, arXiv:1007.2581

  25. Susceptibilities and Moments In the Boltzmann approximation, the HRG model provides a simple result for the thermodynamic pressure. The nth order susceptibilities: X.F. Luo (LBNL/USTC)

  26. High Order Correlations Event by event: net-proton Kurtosis Kp(E)* two proton correlation functions C2(E) ratio of the d/p ratio of K/p * Gavai and Gupta, 03, 05; Gupta 0909.4630 M. Cheng et al. 08 Gupta, Karsch, Stephanov, INT, 08

  27. High Moment Analysis (BES) STAR Preliminary High moments are more sensitive to critical point related fluctuation. The 4th moment, Kurtosis, is directly related to the corresponding thermodynamic quantity: susceptibility for conserved quantum numbers such as Baryon number, charge, strangeness… see H.G. Ritter’s talk

  28. Net-proton High Moments STAR: 1004.4959, PRL STAR results* on net-proton high moments for Au+Au collisions at √sNN= 200, 62.4 and 19.6 GeV. Sensitive to critical point**: Direct comparison with Lattice results**: Extract susceptibilities and freeze-out temperature. An independent test on thermal equilibrium in heavy ion collisions. * STAR: 1004.4959, accepted by PRL(2010). ** M. Stephanov: PRL,102, 032301(2009). *** R.V. Gavai and S. Gupta: 1001.2796. F. Karsch and K. Redlich, arXiv:1007.2581 Estimated errors in Au+Au collision : Run 10: 7.7, 11.5, 39 GeV Run 11: 18, 27 GeV

  29. Example III:Slope Parameters of Hadrons and Leptons

  30. Slope Parameter Systematics Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006

  31. Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization! • Low mass region: • , , e-e+ • minve-e+ • medium effect • Chiral symmetry • -Intermediateregion: • J/e-e+ • minve-e+ • Direct radiation Expanding partonic matter at RHIC and LHC! Direct Radiation Measurements Direct radiation: hadronic partonic STAR already started its di-electron measurements!

  32. QCD Phase Diagram Tch ~ TC(LGT) at RHIC. *Thermalization has been assumed! LHC:Ti, TC RHIC & SPS:TC, TE, andphase boundary FAiR & NICA: Detailed phase structure study Recent review: Andronic, et al, NP A772, 167(06) LHC RHIC ------------------ SPS AGS SISNICA

  33. Many Thanks to Conference Organizers!

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