1. Identified Hadron Production at low to mid p T (~5.0GeV/c) in Au+Au and Cu+Cu Collisions Maya SHIMOMURA University of Tsukuba 2007 年 2 月 10,11 日 heavy ion café 松本合宿

2. Contents Introduction –Baryon Anomaly at RHIC Recent results –Spectra measurements –p/pi ratio for various systems –proton R AA –(models) Summary

3. Introduction

4. Baryon Anomaly ( Baryon Enhancement ) at RHIC PHENIX: PRL 91, 172301 (2003), PRC 69, 034909 (2004), PRC 74, 024904 (2006) R CP (or R AA ) Pions: pT> ２ GeV/c の領域に強い suppression がみられる (jet quenching effect) Protons: p T =2-5 GeV/c の領域で Rcp= ～ 1 になっている

5. Anomalous Composition R cp – メソンとバリオンで違う曲線を描いている  メソンが、他のメソンと同じ振る 舞いをすることから、 mass の違いに よるものではないといえる p/  and  p/  ratios – ｐ T=2~5GeV/c では p/  が  p/  に比べて 大きい –Centrality による違いがはっきりみえる –d+Au, p+p, Au+Au の peripheral は、同じ振 る舞いをする。

6. results

7. Many spectra measurements are done. Phenix preliminary More and more … Au+Au/Cu+Cu/p+p, 22.5/62.4/200 GeV, pi(±,0) and (anti-)proton.

8. Compilation of p/  ratios (central) Cu+Cu 22.5 GeV,  p/   ratio in central agree with p+p. Many protons, mostly from participant nucleons. * No weak decay feed-down correction applied.

9. Compilation of p/  ratios (central) Cu+Cu 62.4 GeV,  p/   ratio larger than those in p+p and Cu+Cu 22.5 GeV. * No weak decay feed-down correction applied.

10. Compilation of p/  ratios (central) Cu+Cu 200 GeV, similar to those in Cu+Cu 62.4 GeV. * No weak decay feed-down correction applied.

11. Compilation of p/  ratios (central) Au+Au 62 GeV,  p/  - is unchanged, p/  + getting larger. * No weak decay feed-down correction applied. Au+Au collision の結果を加えると・・・

12. Compilation of p/  ratios (central) Au+Au 200 GeV,  p/  - is enhanced, p/  + is similar to  p/  - * No weak decay feed-down correction applied.

13. Compilation of p/  ratios (peripheral) Conversing to the same line for both  p/  - and p/  + * No weak decay feed-down correction applied.

14. Centrality dep. of p/  in Au+Au 200 GeV p/  in Au+Au 200 GeV - p/  (pbar/  ) ratios seem to turn over at intermediate p T, and be close to the value of fragmentation at higher p T. - Clear peak in central events than that in peripheral. - Indicating a transition from soft to hard at intermediate p T.

15. - Baryon enhancement observed in Cu+Cu at 200 GeV. - p T dependence in Cu+Cu is similar to that in Au+Au. Centrality dep. of p/  in Cu+Cu 200 GeV Phenix preliminary p/  in Cu+Cu 200 GeV

16. Centrality dep. of p/  in Cu+Cu 22.5 GeV More protons transported to mid rap. instead of production for Cu+Cu 22GeV. Almost no centrality dependence in  p/  .  p/  - ratios are ~0.3-0.4 at p T = 2 GeV/c, which is close to the value in p+p. * No weak decay feed-down correction applied.

17. p/  + ratios are reduced, compared to those in Cu+Cu 22 GeV.  p/  - ratio in central collisions reaches R=~0.6 at p T = 2 GeV/c. Centrality dependence is also seen. Centrality dep. of p/  in Cu+Cu 62.4 GeV * No weak decay feed-down correction applied.

18.  s NN dep. of  p/  - and p/  + ratio (central) Increasing as a function of  s. p-bar/  - と p/  + では、 逆の傾向をしめしている。 decreasing as a function of  s.

19. p/  vs. N part 1/3 Phenix preliminary Cu+Cu 200 GeV vs. Au+Au 200 GeV NOTE: No weak decay feed-down correction applied. TOF (<3 GeV/c) ACC (>3 GeV/c) 0.6 - 1.5 GeV/c1.0 - 2.0 GeV/c2.0 - 3.0 GeV/c3.0 - 4.0 GeV/c4.0 - 5.0 GeV/c pTpT pTpT Phenix preliminary - Centrality dependence in Cu+Cu looks similar to that in Au+Au (N part scaling at same sqrt(s NN )!). - Even though overlap region has a different geometrical shape. - Slight difference in the magnitude seen.

20. R AA vs. p T - Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression) - Suppression is seen for pions, kaons. NOTE: No weak decay feed-down correction applied. Phenix preliminary

21. R AA vs. p T - Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression) - Suppression is seen for pions, kaons. NOTE: No weak decay feed-down correction applied. Phenix preliminary NOTE: Systematic errors (~10%) for overall normalization not shown. - Similar N part dependence for Au+Au / Cu+Cu. (N part scaling of R AA ) - Cronin effect in peripheral

22.  0 R AA, Central Events,Different √s WA98, EPJ C 23, 225 (2002) [ new reference compiled by D.d'Enterria nucl-ex/0403055] PHENIX, PRL 88 022301 (2002) No Suppression at 17 GeV (Au+Au) and 22 GeV (Cu+Cu)at medium p T Need more study for 17~62.4~ GeV data π 0 Au+Au π 0 Cu+Cu

23. R AA Error notations: - Error bars: statistical error for HI spectra - Boxes: 1) sys. error for p+p reference. 2) sys. error for HI spectra. - Lines: N coll error (1 .) Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (p T > 2.0 GeV/c). π ± is similar to π 0

24. Au+Au 200 GeV - Spectra for heavier particles has a convex shape due to radial flow. - Using Blast-wave fitting, try to estimate p/  ratio as a function of p T. (hydro p)/(hydro  ) (hydro p)/(real  ) NOTE: No weak decay feed-down correction applied. CentralPeripheral ｐ T が２ GeV/c 以上の領域は、 hydrodynamics だけでは、 proton enhancement を説明できない。 →recombination や fragmentation の寄与 - Radial flow (ex. blast-wave fit) -

25. Quark Recombination model (+Fragmentation) Example: –Fragmentation: D q→h (z) produces a 6 GeV/c  from a 10 GeV/c quark –Recombination: produces a 6 GeV/c  from two 3 GeV/c quarks produces a 6 GeV/c proton from three 2 GeV/c quarks Fries, et al, nucl-th/0301087 Greco, Ko, Levai, nucl-th/0301093 Mid pT 領域では、衝突で生成された quark が coalesce してハドロンを生 成しているモデル fragmentation recombination p/  Phenix preliminary

26. summary Proton enhancement is observed in Au+Au/Cu+Cu collisions at 200/62 GeV. p/  ratios: 1.Only antiprotons in Cu+Cu 22.5 GeV system is different from others: No centrality dependence in  p/  ratio at the intermediate pT. Central 0-10%  p/  ratio agrees with the value in p+p collisions 2.Indicating a transition from soft to hard production at intermediate pT. 3.Npart scaling (dET/dy scaling) over different collision systems. 4.Recombination + radial flow would explain the p T, N part dependencies. Data indicates that an onset of baryon anomaly at RHIC is in between 22 GeV and 62 GeV.

27. Spectra @High pT

28. Introduction Cronin effect in nuclear. (Initial) Gluon interaction in hot dense matter. (final) The suppression at high pT is due to the final state interaction. Dependence on the System size ? Dependence on the particles species ? *PRL 91 072303 (2003) *No suppression in d+Au collision while Au+Au has factor 3 suppression at high pT. *Direct photon is not suppressed. PR L 94(2005)232301 Comparison between Au+Au and d+Au collision with high energy.

29. Many measurements are done for high pT.

30. Back up ～検出器・解析手法～

31. PID charged p T spectra analysis in PHENIX Detectors: Drift Chamber, PC1, BBC and TOF for PID charged analysis. Centrality: Subdivided minimum bias triggered events, based on BBC charge (62 GeV), or the number of PC1 hit (22 GeV). Corrections: Geometrical acceptance, in flight decay. NOTE: No weak decay feed- down correction applied for all plots in this presentation. Charged particle identification by TOF Charge x Momentum (GeV/c) 1/  Cu+Cu @ 22.5 GeV

32. PHENIX detector Aerogel Cherenkov (PID) EM Calorimeter (PID) TOF (PID) Drift Chamber (momentum meas.) Tracking detectors (PC1,PC2,PC3) - Central Arm Detectors (magnetic spectrometer) - Event Characterization detectors - PID (particle identification) is a powerful tool to study hadron production. p (p) ID up to 7 GeV/c - p (p) ID up to 4 GeV/c - Time of Flight (TOF) Veto for proton ID π+π+ K+K+ p Aerogel Cherenkov (ACC)

33. Back Up ~ 説明 ~

34. R AA Normalization /  inel p+p nucleon-nucleon cross section 1. Compare Au+Au to nucleon-nucleon cross sections 2. Compare Au+Au central/peripheral Nuclear Modification Factor: If no “effects”: R AA < 1 in regime of soft physics R AA = 1 at high-p T where hard scattering dominates Suppression: R AA < 1 at high-p T AA

35. What is the definition of baryon anomaly at RHIC? p T region of interest is the intermediate p T (2.0 - 5.0 GeV/c).  p/  (p/  ) ratios are much larger than the fragmentation expectations (p+p). –Strong centrality dependence in heavy ion data. Different nuclear modification factor (R CP or R AA ) between pions and (anti)protons. –Pions: suppression. –(anti)protons: no suppression.

36. probe rest frame r/  gg  g Color Glass Condensate Gluon fusion reduces number of scattering centers in initial state. Theoretically attractive; limits DGLAP evolution/restores unitarity

37. Back up ～結果～

38. p T spectra in p+p 62.4 GeV Data from Run-6 (2006) at RHIC. Provides an important baseline for p T spectra in Au+Au and Cu+Cu at  s NN = 62.4 GeV. Presented the invariant yields here. Working on the determination of inelastic cross section and trigger bias in PHENIX experiment for the absolute normalization in p T spectra. * No weak decay feed-down correction applied.

39. p T spectra (Cu+Cu √s NN = 200 GeV) NOTE: No weak decay feed-down correction applied. Phenix preliminary - p T reach extended for (anti-)protons with fine centrality bins. <= (1) Aerogel Cherenkov, (2) Enough statistics in Au+Au/Cu+Cu (Anti-) protons ACC

40. p T spectra (p+p √s = 200 GeV) - High statistics 200 GeV p+p data. More than10 times statistics used compared to previous Run3 p+p analysis. - The p+p data provides baseline spectra to heavy ion data, and it is important to quantify in-medium nuclear effects in heavy ion collisions at RHIC. NOTE: No weak decay feed-down correction applied. Phenix preliminary TOF

41. Medium II: Thermalization Hadron yields and spectra are consistent with thermal emission from a strongly expanding source. The observed strangeness production is consistent with complete chemical equilibrium  /K/p measurement in a Broad pt range Stat. model fit:T ch ~ 160MeV,  s ~1.0 Strangeness saturation at RHIC? stronger radial flow at RHIC? Expansion velocity T kin ~ 100 MeV ~ 0.5 Chemical freezeout Thermal freezeout RHIC

42. p/   ratios in p+p 62.4 GeV

43. R AA for charged pions (by ISR fit) Error notations: - Error bars: statistical error for HI spectra - Boxes: 1) sys. error for p+p reference. 2) sys. error for HI spectra. - Lines: N coll error (1 .) Used ISR fit (nucl- ex/0411049, D. d’Enteria) for p+p parameterization. Using ISR fit: Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (p T > 2.0 GeV/c). * No weak decay feed-down correction applied.

44. R AA for antiprotons (by ISR fit) Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference. Similar R AA for all three systems. * No weak decay feed-down correction applied.

45. R AA for protons (by ISR fit) Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference. Largest R AA for Cu+Cu 22.5 GeV. R AA for Au+Au 62.4 GeV is smaller than that in Cu+Cu 62.4 GeV. * No weak decay feed-down correction applied.

46. p/  vs. p T (Low p T ) At low p T, p/  shows weak and decreasing N part dependence because inverse slope (from m T exponential fitting) also shows it. NOTE: No weak decay feed-down correction applied. - Radial flow - (Anti-)protons TOF Phenix preliminary

47. Recombination model と結果の比較 Fries, R et al PRC 68 (2003) 044902 Greco, V et al PRL 90 (2003) 202302 Hwa, R et al PRC 70(2004) 024905 etc. Hydro + Recombination + Fragmentation で、説明できるか？？ Au+Au 200GeV STAR preliminary