1. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20061/20 Search for Partonic EoS in High-Energy Nuclear Collisions Nu Xu Lawrence Berkeley National Laboratory Many thanks to the conference organizers and S. Blyth, S. Esumi, H. Huang, Y. Lu, M. Oldenburg, H. Ritter, K. Schweda, P. Sorensen, Z. Xu, Yifei Zhang M. Bleicher, P. Houvinen, V. Koch, K. Redlich, ….

2. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20062/20 Outline  Motivation - s-quark and c-quark are special - equation of state - collectivity, local thermalization  Particle spectra and v 2 - partonic collectivity from multi-strange hadrons - hint of charm collectivity  Summary and outlook

3. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20063/20 QCD Energy Scale m s ~ 0.2 GeV, similar to values T C critical temperature  QCD QCD scale parameter T CH chemical freeze-out temperature   = 4  f  scale for  symmetry breaking m c ~ 1.2 - 1.5 GeV >>  QCD - pQCD production - parton density at small-x - QCD interaction - medium properties R cc ~ 1/m C => color screening J/  => deconfinement and thermalization u-, d-, s-quarks: light-flavors heavy-flavors c-, b-quarks: heavy-flavors Strange-quark  hadronization Charm-quark  thermalization

4. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20064/20 Equation of State Equation of state: - EOS I : relativistic ideal gas: p =  /3 - EOS H: resonance gas: p ~  /6 - EOS Q: Maxwell construction: T crit = 165 MeV, B 1/4 = 0.23 GeV  lat =1.15 GeV/fm 3 P. Kolb et al., Phys. Rev. C62, 054909 (2000). EOS - the system response to the changes of the thermal conditions - is fixed by its p and T (  ). Energy density  GeV/fm 3

5. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20065/20 Identify and study the properties of matter with partonic degrees of freedom. Penetrating probes Bulk probes - direct photons, leptons - spectra, v 1, v 2 … - “jets” and heavy flavor - partonic collectivity - fluctuations jets - observed high p T hadrons (at RHIC, p T(min) > 3 GeV/c) collectivity - collective motion of observed hadrons, not necessarily reached thermalization among them. Physics Goals at RHIC Hydrodynamic Flow Collectivity Local Thermalization = 

6. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20066/20 High-energy nuclear collisions Initial Condition - initial scatterings - baryon transfer - E T production - parton dof System Evolves - parton interaction - parton/hadron expansion Bulk Freeze-out - hadron dof - interactions stop jets J/  D      K, K*  p  d, HBT elliptic flow v 2 radial flow  T Q2Q2 time partonic scatterings, early thermalization? T C T ch T fo

7. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20067/20 Hadron spectra from RHIC p+p and Au+Au collisions at 200 GeV Multi-strange hadron spectra are exponential in their shapes. STAR white papers - Nucl. Phys. A757, 102(2005).

8. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20068/20 Yields ratio results - In central collisions, thermal model fit well with  S = 1. The system is thermalized at RHIC. - Short-lived resonances show deviations. There is life after chemical freeze-out. RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184. Thermal model fits data T ch = 163 ± 4 MeV  B = 24 ± 4 MeV

9. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 20069/20 Blast wave fits: T fo vs. 1) , K, and p change smoothly from peripheral smoothly from peripheral to central collisions. to central collisions. 2) At the most central collisions,  T  reaches collisions,  T  reaches 0.6c. 0.6c. 3) Multi-strange particles ,  are found at higher T  are found at higher T and lower  T  and lower  T   Sensitive to early partonic stage!  Sensitive to early partonic stage!  How about v 2 ?  How about v 2 ? STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04). 200GeV Au + Au collisions  T  Multi-strange hadrons freeze-out with higher T fo (~T ch ) and smaller  T 

10. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200610/20 Compare with hydro-model results The model results fit to pion, Kaon, and proton spectra well, but over predicted the values of for multi-strange hadrons. Multi-strange hadrons freeze-out earlier! P. Kolb and R. Rapp, Phys. Rev. C62, 054909 (2000).

11. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200611/20 T vs. mass plot (SPS) Interactions with hadronic gas:  Large x-section limit: pions, kaons, protons  Small x-section limit: , J/  sensitive to hadronization! At SPS, the observed collective transverse flow,  ~ 0.4c, develops mostly at the hadronic stage.  and J/  do not flow! H. van Hecke, H. Sorge, N. Xu, Phys. Rev. Lett. 81, 5764(98).

12. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200612/20 Slope parameter systematics At RHIC, , , , and J/  show collective motion in 200 GeV Au + Au central collisions! PHENIX ( , K, p, J/  ): PRC69, 034909(04), QM05; STAR ( , ,  ): QM05. sps

13. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200613/20 y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Anisotropy parameter v 2 Initial/final conditions, EoS, degrees of freedom

14. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200614/20 v 2 of multi-strange hadrons ‘Strangeness’ flows - partonic collectivity at RHIC! * Inconsistencies in current hydro calculations STAR Preliminary, QM05 conference

15. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200615/20 Collectivity, Deconfinement at RHIC - v 2, spectra of light hadrons and multi-strange hadrons - scaling of the number of constituent quarks At RHIC, I believe we have achieved:  Partonic Collectivity  Deconfinement PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04), 95, 122301(05) nucl-ex/0405022 S. Voloshin, NPA715, 379(03) R.J. Fries et al., PRC69, 031902(03) Models: Greco et al, PRC68, 034904(03) X. Dong, et al., Phys. Lett. B597, 328(04). ….

16. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200616/20 Dynamic model results Models seem to work in 2.5 <p T <5 GeV/c In those models, almost no interactions at the late hadronic stage. Flow has developed prior to hadronization:  partonic collectivity  deconfinement * No collective flow in reco calculations

17. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200617/20 However, hadronic transport … RQMD results show the particle type dependence although the absolute amplitudes of v 2 are a factor of 2 or so too small! 1) At low p T region: mass ordering - feature of hydrodynamic motion 2) Hadron type dependence at the intermediate p T region - vacuum hadronic cross sections used in the model. Y. Lu et al., nucl-th/0602009 NCQ-scaling is unique, but the explanation may be not! * Reco versus transport mode calculations.

18. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200618/20  -mesons flow = partonic flow  -mesons are very special: - they do not re-interact in hadronic environment - they are formed via coalescence with thermal s-quarks - they show strong collective flow STAR Preliminary: QM05, M. Lemont, S. Blyth talks

19. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200619/20 Multi-strange hadron ratios In heavy ion collisions at RHIC, up to p T ~ 4 GeV/c, (*model predicts 8 GeV/c) the strangeness production is dominated by the thermal like processes. * Hwa and Yang, nucl-th/0602024; STAR data: QM05, S. Blyth talk STAR Preliminary

20. Nu XuInternational Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 200620/20 Summary and outlook Experimental results from RHIC:  Jet-quenching - hot and dense matter  Strong collective flow -Interacting matter  Chemical freeze-out near the phase boundary   (ss),  (sss), J/  (cc) show partonic collectivity at RHIC (at SPS: , , J/  v 2 should be close to zero) Next Step:  Measure the partonic velocity to infer pressure parameter - important for mapping the EoS at RHIC.  In order to further demonstrate the early partonic thermalization, one needs to measure the heavy-flavor collectivity = light-flavor thermalization - RHIC heavy-flavor program, LHC.  In order to demonstrate the phase transition in high-energy nuclear collisions, one needs to identify the critical point - RHIC low energy scan and GSI CBM experiments.