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

A-A collisions: Naturally provides jet and the QGP I. Jet Quenching Rutherford experiment a  atom discovery of nucleus SLAC DIS experiment e  proton discovery of quarks penetrating beam (jet) absorption or scattering pattern QGP Hard Probes of Quark Matter: 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

27 YEARS AGO

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

Basic Idea for Jet Quenching hadrons q Leading particle suppressed leading particle suppressed hadrons q leading particle leading particle 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

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

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

First Order in opacity Correction

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

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

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

Jet Quenching with Detailed Balance 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 x p Detailed Balance

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

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

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

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)

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

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

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

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

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

Modified Frag. Function in Cold Nuclear Matter hadrons ph 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:

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

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

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

III. Jet Tomography of Strong Interaction Matter 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 Energy loss

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

Expanding Hot Quark Gluon Medium R. Baier et al

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

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

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

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

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

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

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:

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

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.

IV. An explanation of heavy quark energy loss puzzle QGP system is not static, it is a expanding system Reaction plane Y X Flow 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

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

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

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

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:

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

Energy Loss vs. Flow Velocity

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

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

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.

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

Thank You