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A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions

A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions. Han-Zhong Zhang Institute of Particle Physics, Huazhong Normal University, China Co-authors: J. Owens E. Wang X.-N. Wang. Introduction Numerical analysis on single hadron and dihadron production Conclusions.

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A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions

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  1. A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions Han-Zhong Zhang Institute of Particle Physics, Huazhong Normal University, China Co-authors: J. Owens E. Wang X.-N. Wang • Introduction • Numerical analysis on single hadron and dihadron production • Conclusions QuarkMatter2006 Nov. 18 , 2006

  2. I. Introduction leading particle hadrons q q hadrons leading particle Leading particle suppressed hadrons q q hadrons N-N collision A-A collision leading particle suppressed QM 2006 Shanghai Han-Zhong Zhang IOPP Hard Probe Signal of QGP in RHIC and LHC Jet quenching: Induced by multiple scattering in QGP medium, a parton jet will radiate gluon and lose its energy. 2

  3. QM 2006 Shanghai Han-Zhong Zhang IOPP LO analysis of jet quenching in AA: 2→2 processes (tree level) Jet quenching in 2→2 processes A factor K=1.5-2 was put by hand to account for higher order corrections 3

  4. Motivation :1) contribution for higher order correction? 2) find a robust probe of dense matter QM 2006 Shanghai Han-Zhong Zhang IOPP NLO (Next to Leading Order ) corrections: K is absent One-loop corrections Jet quenching in 2→3 processes 2→3processes (tree level) (Jeff. Owens , PRD65(2002)034011; B.W. Harris and J. Owens , PRD65(2002)094032) 4

  5. QM 2006 Shanghai Han-Zhong Zhang IOPP Modified Fragmentation Function (FF) Jet Quenchingeffects lead to the modification of FF KKP (X. -N. Wang , PRC70(2004)031901) where and the averaged scattering number, It determines the thickness of the outer corona where a parton jet survives in the overlapped region. 5

  6. QM 2006 Shanghai Han-Zhong Zhang IOPP In 1-demension expanding medium, the total energy loss: The energy loss with detailed balance: (Enke Wang and Xin-Nian Wang, PRL87(2001)142301) An energy loss parameter proportional to the initial gluon density 6

  7. QM 2006 Shanghai Han-Zhong Zhang IOPP II. Numerical analysis on single hadron and dihadron production 1) fix scales and energy loss parameter 2) the centrality dependent of the suppression factor 3) hadron contour plot 4) fragility of single and dihadron tomography 7

  8. QM 2006 Shanghai Han-Zhong Zhang IOPP The invariant p_T spectra of single hadron p-p data at 200GeV are used to fix scales, 8

  9. QM 2006 Shanghai Han-Zhong Zhang IOPP 0-10% AuAu data at 200GeV are used to fix the energy loss parameter (proportional to the initial gluon density): 9

  10. QM 2006 Shanghai Han-Zhong Zhang IOPP Centrality Dependence 10

  11. Single hadron is dominated by surface emission y emission surface Single hadron x parton jet coronathickness QM 2006 Shanghai Han-Zhong Zhang IOPP completely suppressed Color strength =single hadronyield from partons in the square 11

  12. 1.68 QM 2006 Shanghai Han-Zhong Zhang IOPP is a fragileprobe of dense matter. loses its effectiveness as a good probe of dense matter Similar to the study by K. J. Eskola , H. Honkanen, C. A. Salgado, U. A. Wiedemann, NPA747 (2005) 511-529 12

  13. of dihadron in Au+Au collisions QM 2006 Shanghai Han-Zhong Zhang IOPP No jet quenching in d+Au, Fit dAu data by pp result to fix scales, Invariant mass 0.3 13

  14. QM 2006 Shanghai Han-Zhong Zhang IOPP If no jet quen-ching, 14

  15. PRL95(2005)152301 QM 2006 Shanghai Han-Zhong Zhang IOPP The ratio between the yield/trigger in AA and in pp: If no jet quen-ching, 0.3 15

  16. Dihadron is from surface emission + punch-through jets N y triggered hadron x associated hadron partonic di-jet tangential S punch-through jets 25% left QM 2006 Shanghai Han-Zhong Zhang IOPP Color strength =dihadronyield from partons in the square 16

  17. is a robust probe of dense matter. 1.68 QM 2006 Shanghai Han-Zhong Zhang IOPP at 200GeV Trigger:8GeVat RHIC 17

  18. is a robust probe of dense matter. QM 2006 Shanghai Han-Zhong Zhang IOPP at 5.5TeV LHC Trigger:20GeVat LHC 18

  19. 1) Because of the stronger quenching effects, the single hadron is dominated by surface emission; the dihadron is from surface emission + punch-through jets. 2) The dihadron is more sensitive to the initial gluon density than the single hadron . When becomes fragile in higher energy AA, is a robust probe of dense matter. 3) Without inputing K factor by hand, NLO results fit data well. Because of the additional 2→3processes, NLO contributions behave with stronger quenching effect than LO contributions: QM 2006 Shanghai Han-Zhong Zhang IOPP III. Conclusions 19

  20. QM 2006 Shanghai Han-Zhong Zhang IOPP Thank for your attention! 谢谢！ 20

  21. is the differential 2-body or 3-body phase space element QM 2006 Shanghai Han-Zhong Zhang IOPP The inclusive cross sections for single hadron production: The inclusive cross sections for dihadron production: is the squared matrix elements

  22. QM 2006 Shanghai Han-Zhong Zhang IOPP Hard sphere model

  23. the formula of spectra inAA QM 2006 Shanghai Han-Zhong Zhang IOPP nuclear modification factor

  24. (Shi-Yuan Li and Xin-Nian Wang , PLB527(2002)85) (Enke Wang and Xin-Nian Wang, PRL87(2001)142301) (B. B. Back et al. [PHOBOS collaboration], PRC70(2004)021902) QM 2006 Shanghai Han-Zhong Zhang IOPP

  25. QM 2006 Shanghai Han-Zhong Zhang IOPP Nuclear shadowing effects only in small pT region So in large pT, medium effects only come from Jet Quenching !!!

  26. Invariant mass: How to fix scales: If no medium effects, QM 2006 Shanghai Han-Zhong Zhang IOPP (X. –N. Wang , PLB 595(2004)165

  27. QM 2006 Shanghai Han-Zhong Zhang IOPP The dihadron azimuthal distributions

  28. increases while decreases with collision energy. RHIC LHC QM 2006 Shanghai Han-Zhong Zhang IOPP There are much more punch-through jets in higher energy AA collisions,

  29. is a robust probe of dense matter. QM 2006 Shanghai Han-Zhong Zhang IOPP at 5.5TeV Trigger:20GeVat LHC

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