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High-pT Identified Particle Spectra: Preliminary Results and Spectral Ratios

Analysis of identified particle spectra with preliminary results for quark matter, including motivation, analysis techniques, and spectral ratios. Data known from PHENIX shows strengths and limitations. Techniques include PID via dE/dx and bin counting. Findings suggest no pT dependence for p-/p+ ratios. Central to the study is the enhancement of baryon production at intermediate pT, revealing a baryon/meson splitting in Rcp. Model predictions suggest a variety of non-fragmentation contributions influencing results. Summary highlights advancements in particle identification and production understanding at high pT.

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High-pT Identified Particle Spectra: Preliminary Results and Spectral Ratios

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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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