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HIC03, Montreal , Canada, Jun 27, 2003

QCD Fragmentation Functions for Hard Hadron Production ( with emphasis on charged-hadron/pion ratio ). Xiaofei Zhang Kent State University. HIC03, Montreal , Canada, Jun 27, 2003. based on work:. X. F. Zhang, et al . , PRL, 89,272301 (2002).

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HIC03, Montreal , Canada, Jun 27, 2003

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  1. QCD Fragmentation Functions for Hard Hadron Production(with emphasis on charged-hadron/pion ratio) Xiaofei Zhang Kent State University HIC03, Montreal , Canada, Jun 27, 2003 based on work: X. F. Zhang, et al. , PRL, 89,272301 (2002) X. F. Zhang , et al , hep-ph/0306227 (2003)

  2. New phenomena at RHIC Charged hadron and pion are different!

  3. Enhancement of p/ π, h/π 0-10% 60-92% this talk: Uncertainty in Fragmentation Functions (FF-s) A simple model to explain h/π enhancement from pQCD

  4. pQCD for hard hadron production hadron p hadron FF-s are important for hadron production

  5. Phase space of fragmentation in pp collisions 4GeV 16GeV 8GeV X. Zhang, et. al. , PRL, 89,272301 (2002)

  6. 91.2 GeV full light q charm bottom

  7. 27.8 GeV β=0.5βKKP β=0.8βKKP β=0.8βKKP β=βKKP β= βKKP Large z part of FF-s and p/π ratio in pp Large z part of FF-s have significant effect on p/π

  8. FF-s and p/π ratio at RHIC pQCD x~0.01, gluon PDF-s become very important Gluon FF-s dominate Large z part of gluon FF-s are even less certain, especially for proton! FF sets

  9. Charged-hadron to pion ratio in pp mimic higher twist effect • using Kretzer FF-s • h/π in pp at RHIC can be described by pQCD

  10. place of hard collisions L(b) A simple model for h/π enhancement in Au+Au * Croinin effect in p+A : RpA>1, for pT>2 GeV * At fixed target energies, Cronin effect is not universal ; heavier particle, larger enhancement p>k>π J. W. Cronin et al., Phys. Rev. D 11,3105 (1975) * Cronin effects in pA collisions kT broadening * kT effects: mimic power correction -- power correction is larger for proton than pion -- more phase space for dynamic broadening KT broadening is non-universal for different particles Simple model • Assume suppression factors cancel approximately

  11. h/π enhancement in Au+Au , more central, larger L(b), more enhancement of charged-haron/pion X.F. Zhang and G. Fai , hep-ph/0306227

  12. Cronin effects in dAu EKS anti-shadowing • Difference of RdAu for charged-hadron and pion are • reasonably described using the same parameters

  13. A simple model based on the non-universal kT broadening of different particles can explainboth • h/ π enhancement in central Au+Au collisions • Difference of RdAu for pion and charged hadron Direct prediction of this model: enhancement of h/ π in d+Au Can it explain the difference of RAA between charged-hadron and pion? Intrinsic kT mimics power corrections, systematic study of power correction is needed

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