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Identified particle transverse momentum distributions in 200 GeV Au+Au collisions at RHIC

Identified particle transverse momentum distributions in 200 GeV Au+Au collisions at RHIC. 刘海东 中国科技大学. Main contribution. Identified charged hadron spectra PRL 97 (2006) 152301 (cited by 61 articles ) nucl-ex 0606003 (cited by 26 articles) Light nuclei spectra and v2

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Identified particle transverse momentum distributions in 200 GeV Au+Au collisions at RHIC

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  1. Identified particle transverse momentum distributionsin 200 GeV Au+Aucollisions at RHIC 刘海东 中国科技大学

  2. Main contribution • Identified charged hadron spectra • PRL 97 (2006) 152301 (cited by 61 articles ) nucl-ex 0606003 (cited by 26 articles) • Light nuclei spectra and v2 • J. Phys. G: Nucl. Part Phys. 34(2007) S1087-s1091 (cited by 3 articles ) • International Journal of Modern Physics E， Vol: 16 Issue: 10 (2007) Page: 3280 - 3285 • Anti-baryon phase space density study • nucl-ex/0610035 Submitted to PLB Haidong Liu (USTC)

  3. Outline • Motivation • Detectors and measurement • Results (RHIC run 4 AuAu 200 GeV) Haidong Liu (USTC)

  4. freeze-out QGP and hydrodynamic expansion initial state pre-equilibrium (high Q2 interactions) hadronization Heavy-ion collisions at RHIC Time Physics: 1) Parton distributions in nuclei 2) Initial conditions of the collision 3) A new state of matter – Quark-Gluon Plasma and its properties 4) Hadronization and freeze-out Haidong Liu (USTC)

  5. Particles production • Charged hadron (pions and protons) production • Low pT – hydrodynamic • Intermediate pT – partonic coalescence • High pT – jet fragmentation Haidong Liu (USTC)

  6. pQCD: Color charge and flavor dependence of parton energy loss S. Wicks et al., NPA 784(2007)426 dE/dx(c/b)<dE/dx(uds)< dE/dx(g) Haidong Liu (USTC)

  7. Parton energy loss in HIJING HIJING calculation Study the PID spectra and pbar/p ratios can help to further understand how the g/q jets interact with the medium X.N. Wang: PRC58(2321)1998. Haidong Liu (USTC)

  8. Different mechanisms govern hadron formation in the different kinematic region • Different hadron species may have different sources • Those sources (g/q) may have different behavior when propagating the medium To study those behaviors, PID in large pT range is required! Haidong Liu (USTC)

  9. STAR detectors: TPC & TOFr Time Projection Chamber • Tracking • Ionization energy loss (dE/dx) • A new technology (TOF) ---- • Multi-gap Resistive Plate Chamber • Good timing resolution (<100ps) • Two trays (TOFr+TOFp) for run 4, acceptance~0.01, 120 trays (TOFr) in the future Haidong Liu (USTC)

  10. TPC PID – Hadrons Low & intermediate pT 2.5<pT<3.0 High performance of time resolution PID up to 12 GeV/c High pT Relativistic rising of dE/dx Haidong Liu (USTC)

  11. Pion & proton spectra STAR Collaboration PRL 97 (2006) 152301 PAs: H. Liu, O. Barannikova, L. Ruan and Z. Xu PID up to 12 GeV/c Haidong Liu (USTC)

  12. pT Nuclear Modification factor In central Au+Au collisions: • At 1.5<pT<7 GeV/c, RCP(p+pbar) > RCP() , RCP(p+pbar) shows obvious decreasing trend. • At 4<pT<12 GeV/c, both  and p are strongly suppressed. They approach to each other at about 0.3 Curve:I. Vitev, PLB 639 (2006) 38. Haidong Liu (USTC)

  13. Color charge and flavor dependence of parton energy loss pT High pT Rcp measurements: , p(pbar), e, , 0 Nucl-ex/0607012 PRL 96 (2006) 202301 Rcp(RAA)~0.2 for all these particles! Haidong Liu (USTC)

  14. Anti-particle to particle ratios -/+ are consistent with flat at unity in all pT, no significant centrality dependence. pbar/p ratio: no significant centrality dependence, parton energy loss underpredicts the ratios (X.N. Wang, PRC 58 (2321) 1998). Haidong Liu (USTC)

  15. Proton over pion ratios The p(pbar)/ ratios in Au+Au collisions show strong centrality dependence. In central Au+Au collisions, the p(pbar)/ ratios reach maximum value at pT~2-3 GeV/c, approach the corresponding ratios in p+p, d+Au collisions at pT>5 GeV/c. In general, parton energy loss models underpredict p/ ratios. R.J. Fries, et al., Phys. Rev. Lett. 90 202303 (2003); R. C. Hwa, et al., Phys. Rev. C 70, 024905 (2004); DELPHI Collaboration, Eur. Phy. J. C 5, 585 (1998), Eur. Phy. J. C 17, 207 (2000). Haidong Liu (USTC)

  16. B/M enhancement at intermediate pT STAR Nucl-ex/0601042 1) The relative baryon enhancement is clearly observed in the p/pi ratios at intermediate pT, the similar behavior can also be seen in the /Ks0 ratios. At the same pT region, the NQ scaling of v2 has also been observed. This can be explained by the parton coalescence phenomena. 2) In general, parton energy loss models underpredict p/ ratios. R.J. Fries, et al., Phys. Rev. Lett. 90 202303 (2003); R. C. Hwa, et al., Phys. Rev. C 70, 024905 (2004); DELPHI Collaboration, Eur. Phy. J. C 5, 585 (1998), Eur. Phy. J. C 17, 207 (2000). Haidong Liu (USTC)

  17. Summary • First time to extend PID pt range up to 12 GeV/c for charged pion, kaon and (anti-)proton • First time to observe the similar suppressions for high pt mesons and baryons, which challenges the standard parton energy loss model • Further test the coalescence model in the intermediate pt range Haidong Liu (USTC)

  18. Haidong Liu (USTC)

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