Transcript Discovery of Jet Quenching and Beyond Jet Xin-Nian Wang LBNL, June 29, 05

Discovery of Jet Quenching and Beyond
Jet
Xin-Nian Wang
LBNL, June 29, 05
Discovery of Jet Quenching and Beyond
The 59th Eastern Forum on Science and Technology
Shanghai, June 28-29, 2005
• Introduction: A brief history
• Jet quenching pattern and implications
• Beyond the discovery of jet quenching
Xin-Nian Wang (LBNL)
Jet Tomography
1
4
iq x
em
em
W (q) 
d
xe
A
j
(0)
j

 ( x) A

4

WDIS
  q  q 
   g  2  F1 ( xB )
q 

1   p  q    p  q 

 p  2 q  p  2 q
pq 
q
q


 F2 ( xB )

q2
xB  
2pq
Dynamic System: Photon or dilepton emission
J/Y suppression
QCD Response:
jem ( x)  j ( x)
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• 1982, Bjorken (unpublished): elastic dE/dx too small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
Phys. Rev. Lett. 68, 1480 (1992)
XNW and M. Gyulassy
Gluon Shadowing and Jet Quenching in A+A Collisions at \sqrt{s}=200 AGeV
ET
Away-side suppression or Mono-jet
Azimuthal Anisotropy
Phys. Rev. C 63, 054902 (2001)
XNW
Jet Quenching and Azimuthal Anisotropy of Large pT Spectra in
Non-central High-energy Heavy-ion Collisions
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
eD( zh , Q2 )  D( zh , Q2 )  D( zh , Q2 )

Dq h ( zh , Q 2 )  S
2
Q2

0
d
dz 
 zh


(
z
,
x
)
D
L
q h 
z z 
 z
h
2 1

4







Guo & XNW’00
Modified splitting functions
A
T
1  z C A 2 S qg ( x, xL )
 ( z, xL ) 

A
(1  z )
Nc
f q ( x)
2
(virtual)
Energy Loss
Quark energy loss = energy carried by radiated gluon
Q2
zg 
d
0
1
2
T
 dz
0
1  (1  z )2
2
T

2
T
 kT2

A
CA s2 Tqg ( x, xL )
Nc
f qA ( x)
Two-parton correlation:

y
~
dy



(
y
)
1

cos

g

f qA ( x)
f

TqgA ( x, xL )
2



 2E 
E   Ca C A  d  ( )(   0 ) ln  2 
  
0
R
3
s
BDPM
Gyulassy Vitev Levai
Wang & Wang
Wiedemann; Zakharov
Single spectra in A+A collisions
dE
E (b, r ,  ) 
dx
 0 L
1d

0
  0
d
 ( , b, r  n )
 0 0
 0 0
 ( , b, r ) 
n part (b, r )

Participant
Density
Single spectra
d AB
2
2
2
2
2

K
d
b
d
r
d
r
t
(
r
)
t
(
r
)
dx
d
k
dx
d
k b
1
2 A 1 B 2 
a
a
b
2


dyd pT
abcd
d abcd 1
f a / A ( xa , ka , r1 ) fb / B ( xb , kb , r2 )
Dh / c ( zc )
dt
zc
Dihadron spectra
Dh / c ( zc , Ec ) Dh / d ( zd , Ed )
zc2
zd2
Nuclear Modification Factor
R
AB

 AB
N binary
AB
 NN
N
  d bT AB (b)
2
bin
Wang&Wang
2001
Initial state effect: Shadowing & pt broadening: XNW, PRC61(00)064910
Fai, Papp, and Levai (02)
Vitev & Gyulassy (02)
Vitev (03)
Alberto Accardi (01)
Color dipole model
Kopeliovich et al (02)
Single hadron suppression
Suppression of away-side jet
Ec
Ed
Azimuthal Anisotropy
Single hadron
Intermediate pT: effects of parton coalescence
Partonic Energy Loss at RHIC
 dE 

  13.8  3.9 GeV/fm
 dx 0
0
 ( , r )  0 (r )  ( R  r )

 0  0.2 fm/c
E=10 GeV
 dE 
 0.5 GeV/fm


 dx cold matter
Enke Wang & XNW’2000
Gyulassy & Vitev;
Barnafoldi et al
Muller
Jeon et al
dN g
dy
 1150
0  40 /fm3
Beyond the discovery I: Energy Dependence
of quenching
D. d’Enterria, Hard Probes 2004
63 GeV
Effect of non-Abelian energy loss
Qun Wang & XNW ‘04
Eg=Eq
Eg=2Eq
Beyond the Discovery II
dihadron
Azimuthal Mapping of jet quenching
STAR preliminary
20-60%
20-60%
Beyond the discovery III: Measuring Parton
Energy Loss
ET
pTtrig
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