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Charged pion pT spectra in Au+Au collisions at 62.4 GeV

Charged pion pT spectra in Au+Au collisions at 62.4 GeV. Zhangbu Xu BNL for the STAR Collaboration. Hadron identification: STAR Collaboration, nucl-ex/0309012. T ime P rojection C hamber: 45 padrow, 2 meters (radius), s( dE/dx)  8%, -1< <1

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Charged pion pT spectra in Au+Au collisions at 62.4 GeV

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  1. Charged pion pT spectra in Au+Au collisions at 62.4 GeV Zhangbu Xu BNL for the STAR Collaboration DNP2004, Zhangbu Xu (BNL)

  2. Hadron identification: STAR Collaboration, nucl-ex/0309012 Time Projection Chamber: 45 padrow, 2 meters (radius), s(dE/dx)8%, -1<<1 Multi-gap Resistive Plate Chamber TOFr: 1 tray (~1/200), s(t)=85ps DNP2004, Zhangbu Xu (BNL)

  3. A New Hadron-Blind Detector Hadron identification: STAR Collaboration, nucl-ex/0309012 nucl-ex/0407006 Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!! DNP2004, Zhangbu Xu (BNL)

  4. Log10(dE/dx) Log10(p) Momentum: GeV/c dE/dx of p (K,p) separation: 2s dE/dx at higher pT DNP2004, Zhangbu Xu (BNL)

  5. STAR Preliminary -(K+p) Separation • Worst Contamination: 1-3% at 50% Eff , 10% at 70-90% Eff • 3 Gauss fits: dE/dx(p)>1.3*dE/dx(K)dE/dx(p) as normal Gauss:s=1, mean=0 • -(K+p) Separation: ~1.5-2 DNP2004, Zhangbu Xu (BNL)

  6. Preliminary pion Spectra p+/ p- ratio is about 1 pbar/p ~=0.5 • TPC: • Pion: 0-~0.6GeV/c • Kaon: 0.2-~0.6GeV/c • Proton: 0.2-~1 GeV/c • TPC+TOF: • Pion: 0.-~10 GeV/c • Kaon: 0.2-~3GeV/c • Proton: 0.2-~5 GeV/c • TOF: • Pion: 0.2-~1.6GeV/c • Kaon: 0.2-~1.6GeV/c • Proton: 0.2-~3 GeV/c DNP2004, Zhangbu Xu (BNL)

  7. h/p ratios • h/p peripheral<central but approach each other at pT>5GeV/c for both negative and positive • (K+p)/pPositive=2*Negative50% higher in central than in peripheral • (h++h-)/(p++ p-) about 20% higher in central than in peripheral • p+/ p- ratio is about 1. DNP2004, Zhangbu Xu (BNL)

  8. p Nucl. Mod. Factor • RCP h+- 20% higher than p+- pT=3-4 GeV/cconsistent with h/pi ratio • Vitev prediction at dN/dy=650 • TOFr agrees with dE/dx p+- • ISR pp parametrization same as PHENIX • Estimated Syst. Error: 5-10% DNP2004, Zhangbu Xu (BNL)

  9. STAR Preliminary 0.5<|h|<0.9 Higher  Better dE/dx resolution: longer track, shorter drift distance DNP2004, Zhangbu Xu (BNL)

  10. Conclusions • TPC+TOF =a tracking system+a TOF + a hadron blind detector+RICH+… • Charged pion identification at high pT can be done with STAR TPC (+TOF) • At 62.4GeV Au+Au, h/p ratios depend on charge, centrality and pT • Central collisions: decrease with pT to approach peripheral value (at pT=6-7GeV/c) • Central Collisions: (h+/p+)-(h-/p-)~=1 (pT=3GeV/c) • RCP of h and p different by ~20% • Study h dependence around mid-rapidity • More to come!!! DNP2004, Zhangbu Xu (BNL)

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