HighpT identified particle spectra

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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

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Whats known from data
PHENIX
p/p is independent of pT
p/p ratio increases with pT 3-4 GeV/c
nq-scaling of v2
baryonmeson difference in suppression factors
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TPC Capability
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PID Techniques rdE/dx Fits
K? yield is estimated from K0s and TOF
measurements-
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and bin counting
Contamination
1-3 at 50 Eff , 10 at 70-90 Eff

• Two Counting methods
• K p h - p (1) c1 p c2 KX
  (2)
• c1 p c2 KX (2), where K is constrained by
  K0s
• c1, c2 are K, p contributions, and X is the total
  yield in the counting region

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Pion Spectra
Minimum Bias
Centrality dependence
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Proton Spectra
Centrality dependence
Minimum Bias
Protons are inclusive here and thereafter
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p-/p Ratios
AuAu min.bias
dAu min.bias
200 GeV
AuAu central
No pT or centrality dependence in p-/p ratios
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Ratios
AuAu min.bias
dAu min.bias
200 GeV
AuAu central

• no centrality dependence within errors
• decreases at high pT

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Baryon Production
200 GeV AuAu, top 5

• enhanced in intermediate pT range
• decreases at higher pT

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Baryon production vs. Centrality

• intermediate pT enhancement is higher in
  central events

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Model Predictions
Variety of non-fragmentation contributions in the
intermediate pT range Recombination/coalescence,
SoftQuench all show increase at low pT and a
turnover to a falling distribution at pT3GeV/c

• V. Greco, C.M. Ko, P. Levai, 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).

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Nuclear Modification Factor
200 GeV AuAu, 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
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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