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High-pT identified particle spectra

High-pT identified particle spectra. Olga Barannikova ( Purdue University) For the STAR Collaboration. _ p - , p + , p, p. Motivation Analysis technique Preliminary results Spectra, Ratios, R cp Summary. What’s known from data:. PHENIX. p/p is independent of p T.

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High-pT identified particle spectra

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  1. High-pT identified particle spectra Olga Barannikova (Purdue University) For the STAR Collaboration _ p-, p+, p, p • Motivation • Analysis technique • Preliminary results • Spectra, Ratios, Rcp • Summary Quark Matter 2005

  2. What’s known from data: PHENIX p/p is independent of pT p/p ratio increases with pT ~ 3-4 GeV/c nq-scaling of v2 baryon–meson difference in suppression factors Quark Matter 2005

  3. + _ 3.0<pT<3.5 GeV/c P, GeV/c Ns+10 Particle/Antiparticle ratios can be extracted from h+/h- Proton-pion separation > 2 s p p 3.0<pT<3.5 GeV/c Ns+10 TPC Capability Quark Matter 2005

  4. ns h+ – h- p p p p p K PT, GeV/c width Ns+10 p PT, GeV/c PID Techniques: rdE/dx Fits K yield is estimated from K0s and TOF measurements- Quark Matter 2005

  5. p K STAR Preliminary p …and bin counting: Contamination: 1-3% at 50% Eff , 10% at 70-90% Eff • Two Counting methods: • K + p= h - π(1)c1 p + c2 K=X(2) • c1 p + c2 K=X(2), where K is constrained by K0s • c1, c2 are K, p contributions, and X is the total yield in the counting region Quark Matter 2005

  6. Pion Spectra Minimum Bias: Centrality dependence: Quark Matter 2005

  7. Proton Spectra Minimum Bias: Centrality dependence: Protons are inclusive here and thereafter Quark Matter 2005

  8. p-/p+ Ratios Au+Au min.bias d+Au min.bias 200 GeV Au+Au central No pT or centrality dependence in p-/p+ ratios Quark Matter 2005

  9. pQCD @ 130 GeV • Soft+Quench @ 130 GeV I. Vitev and M. Gyulassy, Nucl. Phys. A 715 779 (2003). Ratios Au+Au min.bias d+Au min.bias 200 GeV Au+Au central • no centrality dependence within errors • decreases at high pT Quark Matter 2005

  10. Baryon Production 200 GeV Au+Au, top 5% • enhanced in intermediate pT range • decreases at higher pT Quark Matter 2005

  11. top 5% • 40-80% central peripheral Baryon production vs. Centrality • intermediate pT enhancement is higher in central events Quark Matter 2005

  12. Model Predictions Variety of non-fragmentation contributions in the intermediate pT range: Recombination/coalescence, Soft+Quench all show increase at low pT and a turnover to a falling distribution at pT~3GeV/c • V. Greco, C.M. Ko, P. L`evai, Phys. Rev. C 68, 034904(2003), Phys. Rev. Lett. 90 202302 (2003). • 200 GeV calculations based on I. Vitev and M. Gyulassy, Phys. Rev. C, 65, 041902(R) (2002). • R. C. Hwa and C. B. Yang, Phys. Rev. C 70, 024905 (2004). Quark Matter 2005

  13. Nuclear Modification Factor 200 GeV Au+Au, Rcp 5 % / 40-80% • Pronounced splitting in the intermediate pT range • Rcp seems lower for pions and higher for protons with respect to NCh at higher pT : • alteration of fragmentation functions by the environment? • __ • p • p Rcp • p- • p+ • No difference between particles and antiparticles Recombination + Fragmentation: R. J. Fries, S. A. Bass, et. al. nucl-th/0306027 Quark Matter 2005

  14. Summary • Particle identification at high pT via relativistic rise in dE/dx; first results on pion and proton identification above 3 GeV/c • p-/p+ 1, no pT dependence for all data sets / centrality bins studied; p/p ratio decreases at high pT towards pQCD expected values • Enhancement in relative baryon to meson production at intermediate pT increases with centrality • Baryon/meson splitting in Rcp at intermediate pT Quark Matter 2005

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