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Resolution of Several Puzzles at Intermediate p T and Recent Developments in Correlation

Resolution of Several Puzzles at Intermediate p T and Recent Developments in Correlation. Rudolph C. Hwa University of Oregon. Quark Matter 05 Budapest, Hungary, August 2005. Work done in collaboration with Chunbin Yang (Hua-Zhong Normal University, Wuhan)

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Resolution of Several Puzzles at Intermediate p T and Recent Developments in Correlation

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  1. Resolution of Several Puzzles at Intermediate pT and Recent Developments in Correlation Rudolph C. Hwa University of Oregon Quark Matter 05 Budapest, Hungary, August 2005

  2. Work done in collaboration with Chunbin Yang(Hua-Zhong Normal University, Wuhan) Rainer Fries(University of Minnesota) Zhiguang Tan(Hua-Zhong Normal University, Wuhan) Charles Chiu(University of Texas, Austin)

  3. QM04 Puzzles at intermediate pT Proton/pion ratio Azimuthal anisotropy Cronin effect in pion and proton production Forward-backward asymmetry in dAu collisions Same-side associated particle distribution

  4. Rp/π Not possible in fragmentation model: u Puzzle #1 Rp/π  1

  5. Proton formation: uud distribution soft component usual fragmentation thermal-shower recombination (by means of recombination) In the recombination model inclusive distribution of pions in any direction

  6. thermal  production in AuAu central collision at 200 GeV fragmentation Hwa & CB Yang, PRC70, 024905 (2004)

  7. All in recombination/ coalescence model compilation by R.Seto (UCR)

  8. STAR data Puzzle #2 Azimuthal anisotropy Molnar and Voloshin, PRL 91, 092301 (2003). Parton coalescence implies that v2(pT) scales with the number of constituents

  9. Cronin Effect Cronin et al, Phys.Rev.D (1975) h q p kT broadening by multiple scattering in the initial state. A p >  Cronin et al, Phys.Rev.D (1975) STAR, PHENIX (2003) Puzzle #3 in pA or dA collisions Unchallenged for ~30 years. If the medium effect is before fragmentation, then  should be independent of h=  or p

  10. Argument does not extend to , nor to higher pT because of ST and SS recombination. RCP for d-Au collisions Hwa & CB Yang, PRL 93, 082302 (04). PRC 70, 037901 (04). because 3q  p, 2q   more partons at 1/3 than at 1/2

  11. forward has more transverse broadening • backward has no broadening Puzzle #4 Forward-backward asymmetry in d+Au collisions If initial transverse broadening of parton gives hadrons at high pT, then Expects more forward particles at high pT than backward particles B/F < 1

  12. Backward-forward ratio at intermed. pT in d+Au collisions (STAR) B/F

  13. Forward production in d+Au collisions BRAHMS data Hwa, Yang, Fries, PRC 71, 024902 (2005) Underlying physics for hadron production is not changed from backward to forward rapidity.

  14. Hwa & Tan, nucl-th/0503060 Recombination model factor of 3 because of T-S recombination difficult for medium modification of fragmentation function to achieve Puzzle #5: Associated particle pT distribution (near side) STAR : nucl-ex/0501016 Trigger 4 < pT < 6 GeV/c

  15. PHENIX (preliminary) N. Grau RIKEN/BNL Workshop 3/05 STAR (preliminary) J. Bielcikova

  16. Correlations Correlation in jets: distributions in  and  2. Two-particle correlation without triggers 3. Autocorrelations 4. Away-side distribution (jet quenching)

  17. P1 Pedestal Why? P2 Are these peaks related? How?  and  distributions

  18. enhanced thermal trigger associated particle peak in  &  Pedestal ForSTSTrecombination with background subtracted

  19. pedestal T=15 MeV Chiu & Hwa, nucl-th/0505014

  20. Chiu & Hwa, nucl-th/0505014

  21. Correlation function Correlation without triggers Normalized correlation function

  22. Correlation of partons in jets A. Two shower partons in a jet in vacuum k Fixed hard parton momentum k (as in e+e- annihilation) x1 x2 kinematically constrained dynamically uncorrelated

  23. no correlation  0 Hwa & Tan, nucl-th/0503052

  24. k q1 q2 q3 q4 Correlation of pions in jets Two-particle distribution The shower partons are anti-correlated

  25. Hwa and Tan, nucl-th/0503052

  26. Hwa and Tan, nucl-th/0503052

  27. Autocorrelation Correlation function 1,2 on equal footing --- no trigger Define Autocorrelation: Fix and , and integrate over all other variables in The only non-trivial contribution to near , would come from jets

  28. x k 1 2 q1  q2 y z parton momentum space P() Gaussian in jet cone x  p1 p2 - 1 2 y z pion momentum space

  29. Chiu and Hwa (05)

  30. Away-side  distribution

  31. Random walker on a circular mount Step size depends on local density Direction of walk is random within a Gaussian peak Most walks are absorbed inside the medium

  32. Sample tracks those that emerge those that are absorbed Chiu & Hwa work in progress away-side distribution

  33. Conclusion • Hadronization by recombination resolves several puzzles at intermediate pT. • The pedestal and peak structure in the near-side jets is due to enhanced thermal partons and to jet cone structure of shower partons. • A dip is predicted in the correlation function due to anti-correlation among the shower partons. • Promising start made in the  distribution on the away-side by simulating parton rescattering and absorption.

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