1. Enke Wang (Institute of Particle Physics, Huazhong Normal University) I.Jet Quenching in QCD-based Model II.Jet Quenching in High-Twist pQCD III.Jet Tomography of Hot and Cold Strong Interaction Matter IV.Modification of Dihadron Frag. Function Jet Quenching Physics

2. Fragmentation Function Evolution: DGLAP Equation

3. hadrons q q leading particle leading particle p-p collision hadrons q q Leading particle suppressed leading particle suppressed A-A collision Jet Quenching: Modification of Fragmentation Function: p

4. 28 YEARS AGO

5. I. Jet Quenching in QCD-based Model G-W (M. Gyulassy, X. –N. Wang) Model: Static Color-Screened Yukawa Potential

6. Opacity Expansion Formulism (GLV) Double Born Scattering GLV, Phys. Rev. Lett. 85 (2000) 5535; Nucl. Phys. B594 (2001) 371 Elastic Scattering

7. First Order in opacity Correction

8. Medium-induced radiation intensity distribution: Induced radiative energy loss: Induced gluon number distribution: Non-Abelian LPM Effect QCD: QED:

9. Radiated Energy Loss vs. Opacity First order in opacity correction is dominant!

10. Detailed Balance Formulism (WW) E. Wang & X.-N. Wang, Phys. Rev. Lett.87 (2001) 142301 Stimulated EmissionThermal Absorption B-E Enhancement Factor 1+N(k) Thermal Distribution Func. N(k)

11. Final-state Radiation Energy loss induced by thermal medium: = Net contribution: Energy gain Stimulated emission increase E loss Thermal absorption decrease E loss

12. First Order in Opacity Correction Single direct rescattering: Double Born virtual interaction: Key Point: Non-Abelian LPM Effect—destructive Interference!

13. Energy Loss in First Order of Opacity Energy loss induced by rescattering in thermal medium: Take limit: Zero Temperature Part: L 2 GLV Result Temperature-dependent Part: Energy gain

14. Numerical Result for Energy Loss Intemediate large E, absorption is important Energy dependence becomes strong Very high energy E, net energy gain can be neglected

15. Parameterization of Jet Quenching with Detailed Balance Effect Average parton energy loss in medium at formation time: Energy loss parameter proportional to the initial gluon density Modified Fragmentation Function (FF) (X. -N. Wang, PRC70(2004)031901)

16. Comparison with PHENIX Data PHENIX, Nucl. Phys. A757 (2005) 184

17. II. Jet Quenching in High-Twist pQCD e-e- Frag. Func.

18. Modified Fragmentation Function Cold nuclear matter or hot QGP medium lead to the modification of fragmentation function

19. Jet Quenching in e-A DIS X.-N. Wang, X. Guo, NPA696 (2001); PRL85 (2000) 3591 e-e-

20. Modified Frag. Function in Cold Nuclear Matter Modified splitting functions Two-parton correlation: LPM

21. Modified Frag. Function in Cold Nuclear Matter hadrons phph parton E are measured, and its QCD evolution tested in e + e -, ep and pp collisions Suppression of leading particles Fragmentation function without medium effect: Fragmentation function with medium effect:

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

23. Heavy Quark Energy Loss in Nuclear Medium LPM Effect 1) Larg or small : 2) Larg or small :

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

25. III. Jet Tomography of Hot and Cold Strong Interaction Matter E. Wang, X.-N. Wang, Phys. Rev. Lett. 89 (2002) 162301 Cold Nuclear Matter: Quark energy loss = energy carried by radiated gluon Energy loss

26. Comparison with HERMES Data HERMES Data: Eur. Phys. J. C20 (2001) 479,,

27. Initial Parton Density and Energy Loss jet1 jet2 Initial energy loss in a static medium with density 0 0.1 fm  0 15 2 A R    GeV/fm Initial parton density (Energy loss ) is 15~30 times that in cold Au nuclei !

28. Comparison with STAR data STAR, Phys. Rev. Lett. 91 (2003) 172302

29. IV. Modification of Dihadron Frag. Function h1h1 h2h2 jet A. Majumder, Enke Wang, X. –N. Wang, Phys. Rev. Lett. 99 (2007 ) 152301 Dihadron fragmentation: h1h1 h2h2

30. DGLAP for Dihadron Fragmentation h1h1 h2h2 h1h1 h2h2 h1h1 h2h2

31. Evolution of Dihadron Frag. Function

33. Medium Modi. of Dihadron Frag. Function

34. Nuclear Modification of Dihadron Frag. Func. e-A DIS

35. Hot Medium Modification

36. Thank You Thank You