相对论重离子碰撞中强子化时刻部分子信息的提取

1. 相对论重离子碰撞中强子化时刻部分子信息的提取相对论重离子碰撞中强子化时刻部分子信息的提取 陈金辉 中国科学院上海应用物理研究所 中国物理学会2008年秋季会议 济南, 山东 2008年9月19号-21号 Many thanks to: The organizer, S. Blyth, 靳富, H. Huang, 马国亮, J. Ma, 马余刚, B. Mohanty, N. Xu and STAR Col.

2. Introduction and Motivation What we have learnt from RHIC data Selected intriguing phenomena at RHIC Analysis and Results Constitute quark pT distribution at hadronization s/d quark ratio at hadronization Summary and Outlook Outline

3. Bulk dense matter produced at RHIC • The disappearance of back-to-back correlation in central Au+Au collisions; • The suppression of high pT particle including he+e-  How does the bulk dense matter hadronize?

4. Intriguing phenomena at RHIC ---- large p/p ratio • Unexpected large p/p ratio in central Au+Au collisions • The hadronization scheme should be different from e+e- !

5. Intriguing phenomena at RHIC ----v2,RCP grouping • V2 and RCP for PID measurement shown a B/M grouping behavior • NCQ-scaling, partonic degree of freedom?

6. What can we learn from those phenomena? • At RHIC intriguing experimental features: • enhanced baryon over meson production • strong elliptic flow • grouping behavior of v2 and RCP for PID ?Hadronization of bulk dense matter created at RHIC should be different from e+e- collisions! ?Quark Coalescence/Recombination ? Evidence for Deconfinement Can we extract the constitute quark pT dis. prior to hadronization from RHIC data?

7. Parton pT distributions at hadronization? If baryons of pT are mostly formed from coalescence of partons at pT/3 and mesons of pT are mostly formed from coalescence of partons at pT/2 [1,2,3] [1] R.C. Hwa et al., PRC 66 (2002) 025205; [2] V. Greco et al., PRL 90 (2003) 202302; [3] R.J. Fries et al., PRL 90 (2003) 202303. • and f particles have no decay feed-down contribution! These particles will freeze-out earlier from the system and have small hadronic rescattering cross sections [4,5]. [4] A. Shor, PRL 54 (1985) 1122; [5] H. Van Hecke et al., PRL 81 (1998) 5764.

8. The s-quark shows a flatter distribution than the d-quark’s • Fitting with a hydro inspired model yield to: s-quark (460 MeV) vT = (0.54 +- 0.13)c Tth = (131 +- 48)MeV d-quark (260 MeV) vT = (0.36 +- 0.19)c Tth = (170 +- 40)MeV • clear KET scaling, partonic evolution described by hydrodynamics Strange and light quark distribution

9. s/d ratio from hyperon X0(1530) feed-down: 46%+-14% • Consistent s/d ratio from primordial hyperon dataS feed-down: no data yet. • Reco. model calculation predicted a consistent shape between s/d ratio and the hyperon ratio.Good agreement with the data;Large exp. uncertainty;The parameterized curve favors large radial flow for strange quark s/d quark ratio

10. Summary and Outlook • We presented constraints on transverse momentum distribution for the effective constituent quarks at hadronization of the bulk partonic matter produced at RHIC. • Our results suggest that strange quarks may have developed • a collective radial flow stronger than that of light quarks during the initial partonic evolution. • The validity of our approach to explore quark transverse-momentum distributions at hadronization has been tested with independent particle ratios. Our approach in complement with the constituent quark number scaling in elliptic flow provides a means to measure quantitative quark properties at hadronization of bulk partonic matter. c.f. Phys. Rev. C 78 (2008) 034907

11. Outlook: Extend PID Capability • /K separation to 1.6 GeV/c (0.7 TPC) • (+K)/p to 3 GeV/c (1.2 TPC) • Clean electron ID down to 0.2 GeV • ToF detector updated: • 5 trays of ToF system installed in Run 8, commissioned, and used for physics. • 90 (of 120) ToF trays to be installed for Run 9 and will be completed before Run 10.

12. sketch by P. Sorensen QGP Hadron gas Outlook: RHIC is ready for the Beam Energy Scan • Key measurements • PID spectra and v2 • K/p , <pT> … fluctuation The location of the QCD Critical Point

13. transport model calculation