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Modification of Fragmentation Function in Strong Interacting Medium

Modification of Fragmentation Function in Strong Interacting Medium. Enke Wang (Institute of Particle Physics, Huazhong Normal University) Introduction Modification of Frag. Func. in Cold Nucleus Modification of Frag. Func. in QGP Medium Summary

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Modification of Fragmentation Function in Strong Interacting Medium

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  1. Modification of Fragmentation Function in Strong Interacting Medium Enke Wang (Institute of Particle Physics, Huazhong Normal University) • Introduction • Modification of Frag. Func. in Cold Nucleus • Modification of Frag. Func. in QGP Medium • Summary Collaborators: X.-N. Wang, B.-W. Zhang

  2. I. Introduction QGP Hard Probes of Quark Matter: penetrating beam (jet) absorption or scattering pattern Rutherford experiment a atom discovery of nucleus SLAC DIS experiment e  proton discoveryof quarks A-A collisions:Naturally provides jet and the QGP Jet (hard probe) created by parton scattering before QGP is formed • high transverse momentum • calculable in pQCD

  3. Jet quenching and Observation Leading particle suppressed hadrons q q hadrons leading particle suppressed Jet Quenching: A-A collision Modification of Fragmentation Function: Particle Production:

  4. Light Quark Energy Loss PHENIX, Nucl. Phys. A757 (2005) 184 Theoretical results from the light quark energy loss is consistent with the experimental data

  5. Heavy quark energy loss: Early Expectations Heavy quark has less dE/dx due to suppression of small angle gluon radiation “Dead Cone” effect B. Zhang, E. Wang, X.-N. Wang, PRL93 (2004) 072301 Y. Dokshitzer & D. Kharzeev PLB 519(2001)199 J. Adams et. al, PRL 91(2003)072304 M. Djordjevic, et. al. PRL 94(2005)112301

  6. No Significant Difference Between Heavy Quark Jet and Light Quark Jet STAR Charged hadrons from Light quark fragmentation Non-photonic electrons from heavy quark decays

  7. Question: Heavy Quark Energy Loss? Theoretical Calculation Energy loss fraction How Reasonable?

  8. II. Modification of Frag. Func. in Cold Nucleus Frag. Func. e-A DIS: e-

  9. Modified Fragmentation Function X.-N. Wang, X. Guo, NPA696 (2001); PRL85 (2000) 3591 Fragmentation function in vacuum Modification term

  10. Modified Frag. Function in Cold Nuclear Medium Modified splitting functions Two-parton correlation: LPM

  11. Rescaling of Modified Fragmentation Function Solid curve: Dashed curve:

  12. Comparison with HERMES Data , , E. Wang, X.-N. Wang, Phys. Rev. Lett. 89 (2002) 162301

  13. Heavy Quark Energy Loss in Cold Nucleus 2) Induced gluon spectra from heavy quark is suppressed by “dead cone” effect Dead cone Suppresses gluon radiation amplitude at B. Zhang, E. Wang, X.-N. Wang, PRL93 (2004) 072301; NPA757 (2005) 493 Mass effects: 1) Formation time of gluon radiation become shorter LPM effect is significantly reduced for heavy quark

  14. Heavy Quark Energy Loss in Nuclear Medium The dependence of the ratio between charm quark and light quark energy loss in a large nucleus The dependence of the ratio between charm quark and light quark energy loss in a large nucleus

  15. III. Modification of Frag. Func. in QGP Medium k k Cold Nucleus Medium QGP Medium

  16. Same Framework for Light and Heavy Quark Light quark: Heavy quark: Peterson form

  17. Generalized Jet Transport Parameter averaged transverse momentum transfer squared per unit distance Unintegrated gluon distribution function: Average tranverse momentum broading:

  18. Jet Energy Loss LPM effect

  19. Modified Frag. Function in QGP Medium Modified splitting functions Parameters:

  20. Modification of Frag. Func. for light quark in QGP can be approached by z Solid Curve: Dashed curve:

  21. Modified Frag. Func. for heavy quark in QGP vacuum medium rescaling medium/vacuum rescaling/vacuum vacuum medium rescaling medium/vacuum rescaling/vacuum E=50GeV E=10GeV z z c quark: can be approached by

  22. vacuum medium rescaling medium/vacuum rescaling/vacuum vacuum medium rescaling medium/vacuum rescaling/vacuum E=10GeV E=50GeV can be approached by b quark: z z

  23. Ratio of energy loss between heavy and light quark in QGP Solid Curve: Dashed curve: c b E • In the intermediate jet energy region the ratio increase rapidly with increasing energy. • In the very high jet energy region the effective energy loss of heavy quark is larger than one of light quark

  24. IV. Summary • The modified fragmentation function in strong interacting medium (cold nucleus and QGP) has been calculated in pQCD. • The modified fragmentation function in QGP medium can be approached by rescaling fragmentation function with effective energy loss fraction. Forlight quark , for heavy quark . • 3)The different effective energy fraction shift of the fragmentation function for light and heavy quark will help us to understand the different behavior of the light and heavy quark jet.

  25. Thank You

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