Nu Xu1/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna High-Energy Nuclear Collisions and the QCD Phase Structure Nu Xu Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley, USA

nuclei hadron gas CSC quark-gluon plasma TETE Baryon Chemical Potential Critical Point? Temperature Early Universe T E RHIC, SPS, FAIR 1 T ini, T C LHC, RHIC 3 Phase boundary RHIC, FAIR, NICA The QCD Phase Diagram and High-Energy Nuclear Collisions

Nu Xu3/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna 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. baryonmeson

Nu Xu4/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Phase Diagram: Water Phase diagram: A map shows that, at given degrees of freedom, how matter organize itself under external conditions. The QCD Phase diagram: structure of matter with quark- and gluon-degrees (color degrees) of freedom.

Nu Xu5/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna E. Fermi: “Notes on Thermodynamics and Statistics ” (1953) Neutron stars QCD Phase Diagram (1953) RHIC

Nu Xu6/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna (1, 2, 5-10)ρ 0 QCD Phase Diagram US Long Range Plan - by Gordon Baym (1, 2, 5-10)*ρ 0 T C ~200 MeV

Nu Xu7/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna QCD Phase Diagram (2009) 1983 US Long Range Plan - by Gordon Baym nucl-th: , NPA830,709(09) L. McLerran nucl-th : 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 (E beam, A) : extract numbers that may be related to the QCD phase diagram!

Nu Xu8/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Outline (1) Introduction (2) STAR experiment and physics program (1) Observables, and recent results - Three examples: (i) v 2 ; (ii) S, K; (iii) di-elelctron - Many more will be discussed during the workshop (2) Summary

Nu Xu9/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna BNL PAC, , 2010 HFT 2013 TPC FGT 2011 STAR Detectors Fast and Full azimuthal particle identification EMC+EEMC+FMS (-1 ≤  ≤ 4) TOF DAQ1000 MTD 2013

Nu Xu10/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Particle Identification at STAR STAR TPC STAR ToF STAR EMC STAR HFT Neutral particles Strange Jets Heavy Quark hyperons Hadrons Multiple-fold correlations among the identified particles! e, μ π K p d TPC ToF TPC Log 10 (p) STAR MTD

Nu Xu11/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna TOF Performance √s NN = 39 GeV Au + Au Collisions TPC TPC+ToF Beam EnergyTiming ResolutionRemarks 200 (GeV)85 (ps) At 39 GeV, using a new calibration scheme without information of start time from VPD, 87 ps of timing resolution has been achieved (GeV)90 (ps) 39 (GeV)85 (ps) 11.5 & 7.7 (GeV)~ 80 (ps)

Nu Xu12/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna 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

Nu Xu13/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna STAR Physics Focus Polarized p+p program - Study proton intrinsic properties Forward program - Study low-x properties, initial condition, search for CGC - Study elastic and inelastic processes in pp2pp 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

Nu Xu14/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna The QCD Critical Point - LGT prediction on the transition temperature T C 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 1 st 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, (00) Res.pdf

Nu Xu15/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Maximum Baryon Density The maximum baryon density at freeze-out: √s NN ~ 8 GeV

Nu Xu16/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Example I: Partonic Collectivity

Nu Xu17/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Anisotropy Parameter v 2 Initial/final conditions, EoS, degrees of freedom

Nu Xu18/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Collectivity, De-confinement at RHIC - v 2 of light hadrons and multi-strange hadrons - scaling by the number of quarks At RHIC:  n q -scaling novel hadronization process êPartonic flow De-confinement PHENIX: PRL91, (03) STAR: PRL92, (04), 95, (05) nucl-ex/ , QM05 S. Voloshin, NPA715, 379(03) Models: Greco et al, PRC68, (03) Chen, Ko, nucl-th/ Nonaka et al. PLB583, 73(04) X. Dong, et al., Phys. Lett. B597, 328(04). …. i ii

Nu Xu19/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna System Size Driven Collectivity Collectivity: Driven by number of participants More Analysis: How and when local equilibrium reached STAR: PRC81, 44902(10)

Nu Xu20/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Low p T (≤ 2 GeV/c): hydrodynamic mass ordering High p T (> 2 GeV/c): number of quarks ordering s-quark hadron: smaller interaction strength in hadronic medium light- and s-quark hadrons: similar v 2 pattern => Partonic Collectivity at RHIC ! Partonic Collectivity at RHIC STAR: preliminary PHENIX: nucl-ex/ QM09: arXiv

Nu Xu21/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna The n q -scaling in Hadron v 2 (a) Scaling for all hadrons up to p T ≥ 3 GeV/c in case of partonic scatterings and coalescence. (b) No scaling in case of hadronic scatterings. (a) Scaling for all hadrons up to p T ≥ 3 GeV/c in case of partonic scatterings and coalescence. (b) No scaling in case of hadronic scatterings.

Nu Xu22/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Observable: Quark Scaling - m  ~ m p ~ 1 GeV - ss   not K + K -   -   h <<  p ,  In the hadronic case: (i)No number of quark scaling (ii)Very small value of  v 2 !  

Nu Xu23/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Example II: High Order Correlation Functions

Nu Xu24/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Correlations, Susceptibilities, Kurtosis Higher order correlations are correspond to higher power of the correlation length of the system: more sensitive to critical phenomena. Skewness: Symmetry of the correlation function. Kurtosis: Peakness of the correlation function. Connection to thermodynamics,  X. Skewness: Symmetry of the correlation function. Kurtosis: Peakness of the correlation function. Connection to thermodynamics,  X. S & K observables: total charge, total protons, net-p, net-Q S & K observables: total charge, total protons, net-p, net-Q M. A. Stephanov, PRL. 102, (09 ) R.V. Gavai and S. Gupta: F. Karsch and K. Redlich, arXiv:

Nu Xu25/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna 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)

Nu Xu26/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna High Order Correlations Event by event: 1.net-proton Kurtosis K p (E)* 2. two proton correlation functions C 2 (E) 3. ratio of the d/p 4. ratio of K/p * Gavai and Gupta, 03, 05; Gupta M. Cheng et al. 08 Gupta, Karsch, Stephanov, INT, 08

Nu Xu27/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna High Moment Analysis (BES) STAR Preliminary 1)High moments are more sensitive to critical point related fluctuation. 2)The 4 th moment, Kurtosis, is directly related to the corresponding thermodynamic quantity: susceptibility for conserved quantum numbers such as Baryon number, charge, strangeness… 3)see H.G. Ritter’s talk

Nu Xu28/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Net-proton High Moments 1)STAR results* on net-proton high moments for Au+Au collisions at √s NN = 200, 62.4 and 19.6 GeV. 2)Sensitive to critical point**: 1)Direct comparison with Lattice results**: 4)Extract susceptibilities and freeze- out temperature. An independent test on thermal equilibrium in heavy ion collisions. * STAR: , accepted by PRL(2010). ** M. Stephanov: PRL,102, (2009). *** R.V. Gavai and S. Gupta: F. Karsch and K. Redlich, arXiv: STAR: , PRL Estimated errors in Au+Au collision : Run 10: 7.7, 11.5, 39 GeV Run 11: 18, 27 GeV

Nu Xu29/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Example III: Slope Parameters of Hadrons and Leptons

Nu Xu30/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Student Lecture, “Quark Matter 2006”, Shanghai, Nov , 2006 Slope Parameter Systematics

Nu Xu31/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna Direct Radiation Measurements Expanding partonic matter at RHIC and LHC! Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization! - Low mass region: , ,   e - e + m inv  e - e + medium effect Chiral symmetry - Intermediate region: J/   e - e + m inv  e - e + Direct radiation hadronic partonic STAR already started its di-electron measurements! Direct radiation:

Nu Xu32/32“Critical Point and Onset of De-confinement”, August, 2010, JINR, Dubna QCD Phase Diagram T ch ~ T C (LGT) at RHIC. *Thermalization has been assumed! LHC: T i, T C RHIC & SPS: T C, T E, and phase boundary FAiR & NICA: Detailed phase structure study Recent review: A.Andronic, et al, NP A772, B.167(06) LHC RHIC SPS AGS SIS NICA

Many Thanks to Conference Organizers!