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

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Presentation on theme: "Yields & elliptic flow of and in Au+Au collisions at"— Presentation transcript:

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 Quark Matter 2006, Shanghai Haidong Liu

3 Introduction (I) Initial Collisions “QGP” Late stage scattering Time “De-confinement” Hadronization Chemical Freeze-out Thermal Freeze-out 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. Quark Matter 2006, Shanghai Haidong Liu

4 (A: atomic mass number)
Introduction (II) (a) Coalescence parameter BA See some detailed discussions at: R. Scheibl, U. Heinz, PRC (1999) (A: atomic mass number) It is defined long time ago, in this paper (b) Access to baryon phase space density F.Q. Wang, N. Xu, PRC (2000) Quark Matter 2006, Shanghai 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? Quark Matter 2006, Shanghai 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 Those models are made in USTC Time Projection Chamber Tracking Ionization energy loss (dE/dx) Coverage -1<<1 Quark Matter 2006, Shanghai Haidong Liu

7 Particles Identification
PID Range (GeV/c): STAR preliminary TOF Quark Matter 2006, Shanghai Haidong Liu

8 Light Nuclei Spectra Deuteron Helium-3 STAR preliminary
Quark Matter 2006, Shanghai Haidong Liu

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

10 Coalescence Parameters B2 & B3
HBT parameters: STAR Phys. Rev. C71 (2005) STAR preliminary STAR preliminary proportional 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 Quark Matter 2006, Shanghai Haidong Liu

11 Light Nuclei Elliptic Flow v2
STAR preliminary This is the 1st helium-3 v2 measurement at RHIC Helium-3 v2 seems deviating from A scaling at higher pT (need more statistics) x y px py Time Coalescence possibility has been weaken when fireball expanded X-direction expands faster than y-direction Non-central collision minBias STAR preliminary Scaled by A Baryon v2 -- X.Dong et al, Phys. Lett. B597 (2004) Quark Matter 2006, Shanghai Haidong Liu

12 Low pT v2 It is expected that heavy particles have negative v2 at low pT pT X-direction Y-direction positive v2 negative v2 pT0 Heavy particles have large pT0, so it’s easier to observe negative v2 for heavy particles BW parameters sensitive STAR preliminary dbar centrality bins: 0~12%, 10~20%, 20~40%, 40~80% pbar v2: STAR Phys. Rev. C72 (2005) The 1st observation of negative v2 at RHIC Quark Matter 2006, Shanghai Haidong Liu

13 Anti-baryon Phase Space Density
STAR preliminary F.Q. Wang, N. Xu, PRC (2000) Mb is nucleon mass 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/ Submitted to PLB Quark Matter 2006, Shanghai Haidong Liu

14 Anti-baryon Phase Space Density
ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)= q+qbar low STAR preliminary Quark Matter 2006, Shanghai Haidong Liu

15 Anti-baryon Phase Space Density
ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)= q+qbar low STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbar low Quark Matter 2006, Shanghai Haidong Liu

16 Anti-baryon Phase Space Density
ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)= q+qbar low STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbar low AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50 q+g, qbar+g high sqrt(sNN)<20 q+g, q+q low Quark Matter 2006, Shanghai Haidong Liu

17 Anti-baryon Phase Space Density
ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)= q+qbar low STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbar low AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50 q+g, qbar+g high sqrt(sNN)<20 q+g, q+q low H1(HERA) p Wp = qqbar+g high Quark Matter 2006, Shanghai Haidong Liu

18 Anti-baryon Phase Space Density
ARGUS e+e- sqrt(s)=9.86() ggg high sqrt(s)= q+qbar low STAR preliminary ALEPH(LEP) e+e- sqrt(s)=91(Z) q+qbar low AGS, SPS, RHIC, ISR, Tevatron nucleus+nucleus (AA, pA, pp, p+pbar) sqrt(sNN)>50 q+g, qbar+g high sqrt(sNN)<20 q+g, q+q low 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 H1(HERA) p Wp = qqbar+g high H. Liu, Z. Xu nucl-ex/ Quark Matter 2006, Shanghai 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+qbar create few anti-baryons (3) Processes q+g create 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 Quark Matter 2006, Shanghai 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. Quark Matter 2006, Shanghai Haidong Liu

21 Summary (II) v2 measurements Anti-baryon phase space density Thanks!
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! Quark Matter 2006, Shanghai Haidong Liu

22 Backup slides Quark Matter 2006, Shanghai Haidong Liu

23 STAR preliminary TOF Quark Matter 2006, Shanghai Haidong Liu

24 H.D. Liu, Z. Xu nucl-ex/ Submitted to PLB Quark Matter 2006, Shanghai Haidong Liu

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

26 Pion & proton Spectra STAR preliminary nucl-ex/0606003
Quark Matter 2006, Shanghai Haidong Liu

27 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) STAR preliminary Method 2: From the measurements of  and  spectra, we can estimate the FD contribution Quark Matter 2006, Shanghai Haidong Liu

28 dbar centrality bins: 0~12%, 10~20%, 20~40%, 40~80%
pbar v2: STAR Phys. Rev. C72 (2005) BW parameters: F. Retiere, M. Lisa, Phys.Rev. C70 (2004) Quark Matter 2006, Shanghai Haidong Liu

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