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Yields & elliptic flow of and in Au+Au collisions at

Yields & elliptic flow of and in Au+Au collisions at . Haidong Liu University of Science & Technology of China For the STAR Collaboration. Outline. Introduction & motivation Measurements Analysis technique Results – spectra; B 2 & B 3 ; v 2

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Yields & elliptic flow of and in Au+Au collisions at

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  1. Yields & elliptic flow of and in Au+Au collisions at Haidong Liu University of Science & Technology of China For the STAR Collaboration

  2. Outline • Introduction & motivation • Measurements • Analysis technique • Results – spectra; B2 & B3; v2 • Discussion: anti-baryon phase space density • Summary Haidong Liu

  3. 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. Introduction (I) Time Late stage scattering Hadronization “De-confinement” Thermal Freeze-out Chemical Freeze-out Haidong Liu

  4. (b) Access to baryon phase space density F.Q. Wang, N. Xu, PRC 61 021904 (2000) Introduction (II) (a) Coalescence parameter BA See some detailed discussions at: R. Scheibl, U. Heinz, PRC 59 1585 (1999) (A: atomic mass number) Haidong Liu

  5. Introduction (III) Coalescence at parton level  hadrons group by their types rather than their mass at intermediate pT (i)Rcp groups by hadron type (ii)v2 follows NQ scaling STAR Nucl. Phys. A 757 (2005) 102 Coalescence at nuclear level  Does the light nuclei v2 follow A scaling? Haidong Liu

  6. STAR Detectors: TPC & TOF • A new technology (TOF) ---- • Multi-gap Resistive Plate Chamber • Good timing resolution, (, K) ~1.6 GeV/c, p ~ 3 GeV/c • 2. 1/100 acceptance (TOFrp) for now, full barrel in the future Time Projection Chamber • Tracking • Ionization energy loss (dE/dx) • Coverage -1<<1 Haidong Liu

  7. Particles Identification PID Range (GeV/c): STAR preliminary TOF Haidong Liu

  8. Light Nuclei Spectra Deuteron Helium-3 STAR preliminary STAR preliminary Haidong Liu

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

  10. Coalescence Parameters B2 & B3 HBT parameters: STAR Phys. Rev. C71 (2005) 044906 STAR preliminary STAR preliminary 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

  11. This is the 1st helium-3 v2 measurement at RHIC • Helium-3 v2 seems deviating from A scaling at higher pT (need more statistics) y py Non-central collision x px Scaled by A • Coalescence possibility has been weaken when fireball expanded • X-direction expands faster than y-direction y x STAR preliminary Time Baryon v2 -- X.Dong et al, Phys. Lett. B597 (2004) 328-332 Light Nuclei Elliptic Flow v2 STAR preliminary minBias Haidong Liu

  12. It is expected that heavy particles have negative v2 at low pT negative v2 positive v2 X-direction Y-direction pT pT0 Heavy particles have large pT0, so it’s easier to observe negative v2 for heavy particles Low pT v2 STAR preliminary 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 Haidong Liu

  13. 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 : H.D. Liu, Z. Xu nucl-ex/0610035 Submitted to PLB Haidong Liu

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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. Summary (I) • With STAR TPC+TOF, spectra and elliptic flow parameter v2 of and have been measured. • Coalescence parameters • The correlation volume is larger in more central collisions. • For beam energy > 20 GeV, B2 doesn’t change with collisions energy indicating a constant correlation volume at freeze-out. • In different centrality collisions, the correlation volumes are proportional to the pion HBT results. Haidong Liu

  21. Summary (II) • v2 measurements • Light nuclei v2 has been measured • The 1st negative v2 at RHIC has been observed (anti-deuteron, pT<0.7) • Anti-baryon phase space density • In nucleus+nucleus collisions, the anti-baryon density can be fitted to a thermal model independent of the beam species • Gluon interactions enhance anti-baryon production Thanks! Haidong Liu

  22. Backup slides Haidong Liu

  23. STAR preliminary TOF Haidong Liu

  24. H.D. Liu, Z. Xu nucl-ex/0610035 Submitted to PLB Haidong Liu

  25. TPC PID – Hadrons STAR preliminary STAR preliminary M. Shao et al., NIMA 558, (419) 2006 Haidong Liu

  26. Pion & proton Spectra STAR preliminary nucl-ex/0606003 Haidong Liu

  27. STAR preliminary 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

  28. dbar centrality bins: 0~12%, 10~20%, 20~40%, 40~80% pbar v2: STAR Phys. Rev. C72 (2005) 014904 BW parameters: F. Retiere, M. Lisa, Phys.Rev. C70 (2004) 044907 Haidong Liu

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