Jet

Discovery of Jet Quenching and Beyond

Xin-Nian WangLBNL, June 29, 05

Discovery of Jet Quenching and Beyond

• Introduction: A brief history

• Jet quenching pattern and implications

• Beyond the discovery of jet quenching

Xin-Nian Wang (LBNL)

Shanghai, June 28-29, 2005

The 59th Eastern Forum on Science and Technology

Jet Tomography

41( ) (0) ( )

4iq x em emW q d xe A j j x A

12

22 2

( )

1 ( )

DIS B

B

q qW g F x

q

p q p qp q p q F x

p q q q

qp

qxB

2

2

Dynamic System: Photon or dilepton emission

J/ suppression

( ) ( )emj x j x QCD Response: Quark scattering

A Chronicle of Jet Quenching

• 1982, Bjorken (unpublished): elastic dE/dx too small• 1990,Gyulassy, Pluemer: Evoking inelastic dE/dx• 1992, Gyulassy, XNW: Suppression of leading hadrons

due to jet quenching• 1994, Gyulassy, XNW: First calculation of radiative

parton energy loss with LPM• 1995, Gyulassy, Pluemer, XNW: Estimate of mono-jet rate

in AA at RHIC• 1996, Huang, Sarcevic, XNW: Medium modified

fragmentation function & gamma tagged jet quenching• 1996, Zakharov: Path integral formulation of dE/dx• 1997, Baier et al: non-abelian LPM in QCD- interaction

with gluonic clouds

A Chronicle- Con’ d

• 2000, XNW: First estimate of Cronin at RHIC• 2000, Gyulassy, Levai, Vitev: Opacity expansion I.• 2001, Wiedemann: Opacity expansion II• 2001, Guo, XNW: Higher-Twist expansion and

calculation of modified frag. function.• 2001, XNW, GVW: high pT v2 due to jet quenching • 2002: Suppression of high pT hadron in Au+Au• 2003: v2 at high pt observed • 2003: Suppression of back-side jet• 2003, June 18: d+Au results announced• 2004, azimuthal dependence of away-side jet• 2005, angular correlations within jets

Jet Quenching

• Jet Quenching – Suppression of high pT jet in dense medium

• Experimentally: – Medium modification of jet fragmentation

function (FF)– Suppression of the leading hadrons in FF

• Theoretically: – Parton energy loss before hadronization – Or absorption of leading hadrons from jets

Single Spectra Suppression

Gluon Shadowing and Jet Quenching in A+A Collisions at \sqrt{s}=200 AGeV

XNW and M. GyulassyPhys. Rev. Lett. 68, 1480 (1992)

ET

Away-side suppression or Mono-jet

Azimuthal Anisotropy

Jet Quenching and Azimuthal Anisotropy of Large pT Spectra in Non-central High-energy Heavy-ion Collisions

Phys. Rev. C 63, 054902 (2001) XNW

Non-suppression in p+A

Systematic study of high p(T) hadron spectra in p p, p A and A A collisions from SPS to RHIC energies

Phys. Rev. C 61, 064910 (2000) hep-ph/9812021, XNW

Experimental Evidence

Modified Fragmentation Function

2 ( , )21( , ) (virtual)

(1 ) ( )

Aqg LA S

L Ac q

T x xCzz x

z N f x

Modified splitting functions

2 2 2( , ) ( , ) ( , )h h hD z Q D z Q D z Q

2 122

40

( , ) ( , )2

h

Q

S hq h h L q h

z

zd dzD z Q z x D

z z

Guo & XNW’00

e-

Energy Loss

2 1 22

2

2 2 20 0

( ,(1 )

(

1 )

)

Q Aqg L

AA s

gq

TcT T T

Czz

Td dz

N

x x

f xk

Two-parton correlation:

0

320( )(

2ln)a

R

A s

EE C C d

BDPMGyulassy Vitev LevaiWang & WangWiedemann; Zakharov

2( , )~ 1 cos

( )( )

Aqg L

gAq f

T x

f

ydy y

x

x

Quark energy loss = energy carried by radiated gluon

Single spectra in A+A collisions

0

0

0

1 0 0

( , , ) ( , , )L

d

dEE b r d b r n

dx

0 0( , , ) ( , )partb r n b r

ParticipantDensity

2 2 2 2 21 2 1 22

( ) ( )ABA B a a b b

abcdT

dK d b d rd r t r t r dx d k dx d k

dyd p

/ 1 // 2( , , )1

( )( , , ) ab cda A a a b B b b h c c

c

df x k r f x k r

dD z

zt

Single spectra

/ /2 2

( , ) ( , )h c c c h d d d

c d

D z E D z E

z z

Dihadron spectra

Nuclear Modification Factor

NNAB

ABAB

NR

binary

)(2 bbTdN ABbin

Initial state effect: Shadowing & pt broadening: XNW, PRC61(00)064910

Fai, Papp, and Levai (02)

Vitev & Gyulassy (02)

Vitev (03)

Color dipole model

Kopeliovich et al (02)

Alberto Accardi (01)

Wang&Wang2001

Single hadron suppression

Suppression of away-side jet

cE

dE

Azimuthal Anisotropy

Single hadron

Intermediate pT: effects of parton coalescence

Partonic Energy Loss at RHIC

00( , ) ( ) ( )r r R r

E=10 GeV0

13.8 3.9 GeV/fmdE

dx

cold matter

0.5 GeV/fmdE

dx

0 0.2 fm/c

Gyulassy & Vitev;Barnafoldi et alMullerJeon et al

30

1150

40 /fm

gdN

dy

Enke Wang & XNW’2000

Beyond the discovery I: Energy Dependence of quenching

D. d’Enterria, Hard Probes 2004

63 GeV

Effect of non-Abelian energy loss

Eg=Eq

Eg=2Eq

Qun Wang & XNW ‘04

Beyond the Discovery II

dihadron

20-60%

STAR preliminary

20-60%

Azimuthal Mapping of jet quenching

Beyond the discovery III: Measuring Parton Energy Loss

ET

pTtrig

STA

R p

relim

inar

y

STA

R p

relim

inar

y

Beyond the discovery V: Mod. FF

Beyond the discovery IV: Abnormal angular distribution

Summary

• Discovery of Jet Quenching proves that dense matter is formed

• Jet quenching is caused by partonic energy loss• Dense matter at RHIC is 30 times higher than

cold nuclei• The matter is strongly interactive• Jet tomography become useful and power tool

for studying properties of dense matter

Theoretical work in China

• Enke Wang, Benwei Zhang, Hanzhong Zhang, W.C. Xiang etc (IOPP, Wuhan)

• S.Y. Li, Z.G. Shi (Shandong Univ.)

• Qun Wang (USTC)

Collaboration with experimental groups