Jet Quenching and Its effects in Strong Interaction Matter

1. Jet Quenching and Its effects in Strong Interaction Matter Enke Wang (Institute of Particle Physics, Huazhong Normal University) • Jet Quenching • Modification of Hadron Fragmentation Function • Jet Tomography of Strong Interaction Matter • An explanation of heavy quark energy loss puzzle • Summary and Discussion

2. I. Jet Quenching 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. 27 YEARS AGO

4. Brief History of Theoretical Research about Jet Quenching 1982: J. D. Bjoken: Fermilab-pub-82/59-THY Energy loss in elastic scattering 1992/1995: X.-N. Wang, M. Gyulassy: PRL68(92) 148, PRD45 (92)844, NPB420(94)583, PRD51(95)3436 Energy loss is dominated by gluon radiation 1995/1997: BDMPS (R. Baier, Yu. L. Dokshitzer, A. Mueller, S. Peigue, D.Schiff) :PLB345(95) 277, NPB478(96)577,NPB483(97)291,NPB484(97)265 Gluon multiple scattering and gluon radiation 2000: GLV(M. Gyulassy, P. Levai, I. Vitev): PRL85(00)5535, NPB594(01)371 U. Wiedemann: NPB588(2000)303 Opacity expansion 2001/2002: E. Wang, X.-N. Wang: PRL87(01)142301, PRL89(02)162301 Detailed Balance; Jet Tomography

5. Basic Idea for Jet Quenching leading particle hadrons q q hadrons leading particle Leading particle suppressed hadrons q q hadrons leading particle suppressed p-p collision A-A collision • At RHIC: • Hard/Semihard processes is important • High- Pt parton (jet) • Jet quenching • Jet production dominates particle yields • at high Pt Suppression of high Pt hadron spectra

6. 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:

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

8. First Order in opacity Correction

9. First Order in opacity Correction Induced gluon number distribution: Non-Abelian LPM Effect Medium-induced radiation intensity distribution: Induced radiative energy loss: QCD: QED:

10. Higher order in Opacity Reaction Operator Approach: (GLV) Induced gluon number distribution: Non-Abelian LPM Effect

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

12. Jet Quenching with Detailed Balance p x 0 E. Wang, X.-N. Wang, Phys. Rev. Lett. 87 (2001) 142301 Temperature and Density QGP System Gluon radiation: E loss Net energy loss of jet: Gluon absorption E absorption Detailed Balance

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

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

15. 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

16. 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)

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

18. II. Modification of Hadron Fragmentation Function e- Frag. Func. e-A DIS

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

20. Twist-four calculation e- X.-N. Wang, X. Guo, NPA696 (2001); PRL85 (2000) 3591

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

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

23. Heavy Quark Energy Loss in Nuclear Medium 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 time become shorter LPM effect is significantly reduced for heavy quark

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

25. 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

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

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

28. Expanding Hot Quark Gluon Medium R. Baier et al

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

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

31. Tomography of Jet quenching in QGP Medium in NLO • 1) Single jet  Single hadron spectra • 2) Dijet  Hadron-triggered away-side hadron spectra • 3) Gamma-jet  Photon-triggered away-side hadron spectra Single jet Dijet Gamma-jet

32. y emission surface Single hadron x parton jet coronathickness Surface Emission of Single Hadron Production H. Zhang, J. F. Owens, E. Wang and X.-N. Wang , Phys. Rev. Lett. 98 (2007) 212301 completely suppressed

33. y triggered hadron x associated hadron partonic di-jet punch-through jets tangential 25% left Surface Emission + Punch-through jet in Dihadron Production Color strength =dihadronyield from partons in the square

34. Prediction at LHC At LHC Surface emission bias single hadron dihadron punch-jets

35. Gamma-jet by NLO pQCD parton model LO (tree level): NLO corrections: (e.g. 23) hadrons with transverse momentum may be larger than that of the photon Fix triger:

36. Gamma-Hadron Suppressions Factor • NLO radiative corrections lead to hadrons with z_T>1, surface emission, • z_T<0.6, volume emission, more sensitive to \eps_0 • 0.6<z_T<1.4, competition of two mechanisms of hadron emssions. • Similarity in value between I_AA for dihadron and Gam-hadron. H.Z. Zhang, J.F. Owens, E. Wang and X.-N. Wang , PRL 103 (2009) 032302

37. Tomography of surface and volume emissions • The spatial transverse distribution of the initial Gama-jet production vertexes that contribute to the Gama-hadron pairs with given values of z_T. • The color strength : Gama-hadron yield • Projections of the contour plots onto y-axes . At large z_T, jet emissions in the outer corona, no energy loss. At small z_T, jets emisions near the center of the medium, energy loss.

38. Flow Y Reaction plane Flow X IV. An explanation of heavy quark energy loss puzzle QGP system is not static, it is a expanding system QED: Static Charge: Coulomb electric field Moving Charge: electric and magnetic field QCD: Static Target: static color-electric field Moving Target: color-electric and color-magnetic field

39. Puzzle for Heavy Quark Energy Loss 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

40. 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

41. Interaction Potential with Flow system fixed at target parton: Static potential system for observer: Lorentz boost from system

42. New Model Potential with Flow Four-vector potential : • The features of the new potential: • Collective flow produces a color-magnetic field • 2) non-zero energy transfor:

43. Dead Cone Reduce Significantly with Flow Dead Cone: Reason: Collective flow changes the poles of the propagator

44. Energy Loss vs. Flow Velocity

45. Average Flow Velocity and Effective Average Energy Loss Average Flow Velocity: 3D ideal Hydrodynamic simulation for 0-10% central events of Au-Au collisions at RHIC energy: Effective Average Energy Loss:

46. Numerical Results of Effective Average Energy Loss 3D ideal Hydrodynamic simulation for 0-10% central events of Au-Au collisions at RHIC energy

47. V.Summary and Discussion • Jet can be used as a hard probe to explore the QGP. • Jet quenching lead to modification of hadron fragmentation function, which result in the suppression of high transverse momentum spectra observed in experiment. • Different tomography picture of the QGP for single jet, dijet and gamma-jet: surface vs. volume emission. • New potential for the interaction of a hard jet with the parton target has been derived. Collective flow reduce significantly the dead cone from mass effect for heavy quark jet. Heavy quark energy loss increase obviously in the presence of collective flow. An explanation of heavy quark loss puzzle is given in the framework of jet quenching theory.

48. Discussion 1) Dihadron azimuthal correlations in head-on collisions in AMPT : Talk this afternoon by Qingjun Liu 2) Multiple parton scattering and modified fragmentation function in medium: Talk this afternoon by Weitian Deng 3) Gamma-jet tomography of high-energy nuclear collisions in NLO pQCD: Talk this afternoon by Hangzhong Zhang

49. Thank You