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Production of meson, baryon and light nuclei in Au+Au collisions at RHIC

Production of meson, baryon and light nuclei in Au+Au collisions at RHIC. Haidong Liu Univ. of Science & Technology of China. Outline. Motivation and introductions Detectors and techniques Results (RHIC run 4 AuAu 200 GeV) Conclusions & Discussions. Motivations & Introductions.

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Production of meson, baryon and light nuclei in Au+Au collisions at RHIC

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  1. Production of meson, baryon and light nucleiin Au+Aucollisions at RHIC Haidong Liu Univ. of Science & Technology of China

  2. Outline • Motivation and introductions • Detectors and techniques • Results (RHIC run 4 AuAu 200 GeV) • Conclusions & Discussions Haidong Liu

  3. Motivations & Introductions Haidong Liu

  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

  5. Particles production • Pions and protons production • Low pT – hydrodynamic • Intermediate pT – partonic coalescence • High pT – jet fragmentation • Light nuclei production • Final-state coalescence Haidong Liu

  6. The success of hydrodynamic STAR PRC.72 (2005) 014904 At low pT, hydrodynamical models successfully reproduce the spectra and v2 Haidong Liu

  7. fragmenting parton: ph = z p, z<1 recombining partons: p1+p2=ph Coalescence NQ scaling of v2 is a strong evidence Coalescence at intermediate pT STAR PRC.72 (2005) 014904 Haidong Liu

  8. Coalescence at intermediate pT STAR: Nucl. Phys. A 757 (2005) 102 The difference is not sensitive to the mass of the hadron, but rather depends on the number of valence quarks contained within it. Haidong Liu

  9. High pT – from pp to AuAu We understand pp collisions • p+p collisions • Parton Distribution Function (derived from e-h scattering) • pQCD (parton-parton interaction cross section calculation) • Fragmentation Function (derived from e+e- collisions) • Au+Au collisions • pp collisions + Nuclear effect Haidong Liu

  10. Jet fragmentation in pp collisions • Improved FF reasonably reproduces data • pbar/p ~ 0.2 at RHIC, <<0.1 at low energypbar dominated by gluon FF PLB 637 (2006) 161 Haidong Liu

  11. Jet quenching in Au+Au Significant suppression of inclusive charged hadron is observed in central Au+Au collisions: Fragmentation+parton energy loss STAR: Nucl. Phys. A 757 (2005) 102 Haidong Liu

  12. 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

  13. 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

  14. The roles of energetic parton --- source of the meson/baryon production (1)In LEP e+e- experiment, identified charged particle spectra can be measured from 2 kinds of hadronic Z decays: quark jets and gluon jets (DELPHI EPJC 17 (2000) 207) (2) The anti-baryon phase space density can be accessed by measuring dbar/pbar F.Q. Wang, N. Xu, PRC 61 021904 (2000) Haidong Liu

  15. 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

  16. Initial Collisions “QGP” Due to the small binding energy, light nuclei cannot survive before thermal freeze-out. Therefore, light nuclei production and their elliptic flow are sensitive to the freeze-out conditions, such as temperature, particle density, local correlation volume and collective motion. Light nuclei formation – final-state coalescence Time Late stage scattering Hadronization “De-confinement” Thermal Freeze-out Chemical Freeze-out Haidong Liu

  17. Final-state Coalescence • Coalescence parameters BA R. Scheibl, U. Heinz, PRC 59 1585 (1999) • Light nuclei v2 – atomic mass number (A) scaling? • (consequence of the final-state coalescence) Haidong Liu

  18. Detectors & Techniques Haidong Liu

  19. STAR detectors: TPC & TOF 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

  20. 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

  21. Light Nuclei Identification PID Range (GeV/c): TOF Haidong Liu

  22. Feed-down correction for (anti-)protons Method 1: Primordial protons and the protons come from weak decays have different DCA distribution Primordial (MC) From decay (MC) Method 2: From the measurements of  and  spectra, we can estimate the FD contribution Haidong Liu

  23. Results (Au+Au 200 GeV) Pion and proton spectra: STAR Phys. Rev. Lett. 97 (2006) 152301 Nuclei spectra and v2: QM06 proceeding, J. Phys. G: Nucl. Part. Phys. 34 (2007) S1087-S1091 Haidong Liu

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

  25. 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

  26. 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

  27. 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

  28. Light Nuclei Spectra Deuteron Helium-3 QM06 proceeding: J. Phys. G: Nucl.Part. Phys. 34 (2007) S1087-S1091 Haidong Liu

  29. Coalescence Parameters B2 & B3 (anti-)proton spectra: STAR Phys. Rev. Lett. 97, 152301 (2006) • B2 & sqrt(B3) are consistent • Strong centrality dependence Haidong Liu

  30. Coalescence Parameters B2 & B3 HBT parameters: STAR Phys. Rev. C71 (2005) 044906 Assuming a Gaussian shape in all 3 dimensions R. Scheibl et al.Phys.Rev.C59 (1999)1585 • Compare to pion HBT results • Beam energy dependence Haidong Liu

  31. Scaled by A Baryon v2 -- X.Dong et al, Phys. Lett. B597 (2004) 328-332 Light Nuclei v2 minBias • This is the 1st helium-3 v2 measurement at RHIC • Deuterons v2 follows A scaling within error bars • Helium-3 v2 seems deviating from A scaling at higher pT (need more statistics) Haidong Liu

  32. BW parameters: F. Retiere, M. Lisa, Phys.Rev. C70 (2004) 044907 Low pT v2 dbar centrality bins: 0~12%, 10~20%, 20~40%, 40~80% pbar v2: STAR Phys. Rev. C72 (2005) 014904 The 1st observation of negative v2 at RHIC No model can readily reproduce the data Haidong Liu

  33. Accessing anti-baryon density by & Source of anti-baryon production H. Liu & Z. Xu, nucl-ex/0610035 Submitted to PLB Haidong Liu

  34. STAR preliminary Anti-baryon Phase Space Density F.Q. Wang, N. Xu, PRC 61 021904 (2000) In nucleus+nuclues collisions, the anti-baryon density increases with beam energy and reaches a plateau above ISR beam energy regardless the beam species (pp, pA, AA). It can be fitted to a thermal model : Haidong Liu

  35. ARGUS e+e- sqrt(s)=9.86() ggghigh sqrt(s)=10 q+qbarlow Anti-baryon Phase Space Density STAR preliminary Haidong Liu

  36. Anti-baryon Phase Space Density ARGUS e+e- sqrt(s)=9.86() ggghigh sqrt(s)=10 q+qbarlow STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbarlow Haidong Liu

  37. Anti-baryon Phase Space Density ARGUS e+e- sqrt(s)=9.86() ggghigh sqrt(s)=10 q+qbarlow STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbarlow AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50q+g, qbar+ghigh sqrt(sNN)<20 q+g, q+qlow Haidong Liu

  38. Anti-baryon Phase Space Density ARGUS e+e- sqrt(s)=9.86() ggghigh sqrt(s)=10 q+qbarlow STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbarlow AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50q+g, qbar+ghigh sqrt(sNN)<20 q+g, q+qlow H1(HERA) p Wp =200qqbar+ghigh Haidong Liu

  39. In e+e-, the density through qqbar processes is a factor of strong coupling constant less than that through ggg processes (s=0.12) (q+qbar->q+qbar+g) s Anti-baryon Phase Space Density ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)=10 q+qbarlow STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbarlow AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50q+g, qbar+g high sqrt(sNN)<20 q+g, q+qlow H1(HERA) p Wp =200qqbar+g high H. Liu, Z. Xu nucl-ex/0610035 Haidong Liu

  40. Where does (anti-)baryon come from? Conclusions: (1) Collisions which contain ggg, qbar+g or qqbar+g processes have higher anti-baryon phase space density (2) Processes q+qbarcreate few anti-baryons (3) Processes q+gcreate few anti-baryons at low energy – energy too low? STAR preliminary In short, anti-baryon phase space density from collisions involving a gluon is much higher than those without gluons Haidong Liu

  41. Conclusions & Discussions Haidong Liu

  42. B/M enhancement at intermediate pT STAR Nucl-ex/0601042 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. Haidong Liu

  43. Freeze-out volumes • B2 and B3 have strong centrality dependence, the system has larger freeze-out volumes in more central collisions. • B2 and sqrt(B3) have similar values in different centrality collisions, which indicates that the deuteron and helium-3 have similar freeze-out volume. • B2 has little beam energy dependence when sqrt(sNN)>20 GeV, which indicates that the freeze-out volume won’t change with the beam energy. Haidong Liu

  44. Light nuclei v2 • At intermediate pT, deuteron v2 follows A scaling within errors while helium-3 v2 seems deviates from this scaling, we need more statistics to draw further conclusion. • At low pT, the dbar v2 is found to be negative. The BW model, which includes large radial flow scenario, also shows a negative flow prediction. But the BW model fails to reproduce our data since there is only mass input for light nuclei. Haidong Liu

  45. 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

  46. Color charge and flavor dependence of parton energy loss pQCD calculations • The partonic source: • , , 0 – light quarks • p(pbar) – glouns • e – heavy quarks S. Wicks et al., NPA 784(2007)426 ??? Rcp(RAA)~0.2 for all these particles! dE/dx(c/b)<dE/dx(uds)< dE/dx(g) Haidong Liu

  47. Physics possible:g/q jets conversion in the medium hard q(qbar) + soft g soft q(qbar) + hard g Compton-like scattering: W. Liu et al.,nucl-th/0607047 A much larger cross-section is needed to explain our data Haidong Liu

  48. And, there is also possible to discover Antihypernucleus The future – a good time for discovery Inv. Yield~ Anti-3He : dbar : pbar 1 : 1K : 1M In the RHIC upcoming high statistics AuAu runs, with STAR large acceptance detector TPC/TOF, we should try to search for anti-, which has never been observed before. E864 Phys. Rev. Lett. 85 (2000) 2685 Thanks! STAR Phys. Rev. Lett. 87 (2001) 262301 Haidong Liu

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