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Single & Dihadron Suppression at RHIC and LHC
Xin-Nian WangLawrence Berkeley National Laboratory
Last call for prediction for LHC, CERN, May 29-June 2,2007
Collaborators: J. Owens, E. Wang, Z. Zhang, Phys. Rev. Lett. 98, 21230 (2007) [nucl-th/0701045]
Outline
• Jet quenching in twist expansion framework
• Single and dihadron suppression at RHIC and LHC
• A roadmap for jet study at LHC
Jet Quenching in A+A Collisions
hadrons
q
q
hadrons
leadingparticle
leading particle
N-N collision
hadrons
q
q
hadrons
Leading particle suppressed
leading particle suppressed
A-A collision
Alphabets of jet quenching
• Gyulassy-Levai-Vitev (GLV)– (Djordjevic, Wicks, Horowitz, …)
• Armesto-Salgado-Wiedeman (ASW)– (Dainess et al, Arleo, Renk, Eskola, …)
• Arnold-Moore-Yaffe (AMY)• High-Twist Expansion (THE)(XNW, Guo,
Majumder, Osborne, Owens, E. Wang, B. Zhang, H. Zhang,…)
Comparative study of jet quenching schemes; A. Majumder QM06 (nucl-th/0702066 )
Jet Quenching in High-Twist Expansion
2 1 22
40 0
1 (1 ) ( , )
( )
Q
s
Aqg L
s Aq
TT
E zd dz
E
T x x
f x
_2 1
( )1 2 1 2
( )2 1
( , ) (0) ( ) ( ) ( )2 2
1 ( ) ( )1
B L
L L
i x x p y
ix p y ix p y
Aqg L
y
dyT x x dy dy A y F y F y A
y
e
e e y y
2 122
40
( , ) ( , ) ( )2
H
Q
S hq h h L q h
z
zd dzD z Q z x D g h
z z
2 ( , ) 21( , ) (virtual)
(1 ) ( )
Aqg L A S
L Aq c
T x x Czz x
z f x N
Gluon distribution of the medium
(0) 1 )[1 cos( )]( , )
) (( )
(T LixAqg L ix p
Lq
pA
F Fe eT x x
dy x p ydf x
[1[ ( ) cos( , )
( )( ) ( ( )]( ) )]
Aqg L
s s T T L T T LLAq
x G xT x x
d y x p yx xx
G xy xf
21( , ) (0) ( , )
2T Tixp i i
T T i T
dx q d e p F F p
p
q ξξ ξ
2
2( ) ( , )
(2 )T
T
d qxG x x q
2 / 2ˆ ˆ( , ) , |( )
T TT x q Ep
q E y q x y
pT broadening and gluon distribution
2 2 2
2 2 ( ) ( , )
1 (2 )R T T
Tc
g C d q qdx x x q
N s
2 22
ˆ qdq dq q
dq
22
2ˆ 4 ( ) ( )
21s A
T Tc
T
qx
Cq x G x
pN E
4 22 4
4 2
12 (( ) ) (0) ( )
2 (2 ) 1iqR
c
d q g Ck q d e p A A p
s N
k=E
pq
Elastic Energy Loss
2 12 22
40 0
1 (1 )( )( c )) 1 os(
Q
A sT L L
c Tg L
C zd dz x G xz x p yd y
Ny
0( ) ( ) 1
( , )( )
( )L
Aq ix p y
Ag
LA x
LL
q
dy y xGT
x ex x
x G xf x
+ + +….
2 22
4
1 (1 )2 ( )
2A
q a q g s L a Lc
C d zdz x G x
N z
0
20 0
/2( ) ( ) ( 1)
2 1g L g Lp T
dp py G x d x
e
Elastic vs. Radiative Energy Loss
2
22
21 cos( )
1 cos( )12 (3)
( )2
ˆ( )
gel
Tg T
L
TLE x p ydy
dy
dy d
d
q y x p yT
21
2 12 (3)T
2 22
4
1 (1ˆ
)[1 cos( ) ( )]
2 (1 )Rad c s T
TT
qE N z y
dy d dzE Ez z
y
2
9 (3)ln 10
2 11rad c
sel
E N ELLT
E
For E=10 GeV, T=0.2 GeV, L=6 fm, s=0.3
Quark-quark Scattering
2 1 22 2
20 0
( )1 (1 )
1 cos(2
) ( )Q
Fs T Lq L
c T
C dz zdy yz d x p y
Nx
qf
z p
arXiv:0704.0106 [hep-ph]
Schafer, XNW and B.Zhang,
Gluon –parton scattering
Coupled equation for modified fragmentation functions forQuarks and gluons
NLO pQCD Calculation
0
0
0
1 0 0
( , , )L
q gd
dEE d b r n
dL
1-D expanding
0 0g
10
.20 0
1
( / 1.6) /(7.5 / )d
dEE E
dL
Energy loss parameter
0 0 0ˆ1.6 A sCq
Transport coefficient
Geometry: Hard Sphere: Good approximation to Wood-Saxon
Single and Dihadron hadron suppression at RHIC
00
zT=pTass/pT
trig
Sensitivity to initial density
2
20 0ˆ 1 2 GeVAq
2
Surface emission?
Surface vs. Volume
Multiplicity at LHC
2dN/dpart
Parton Shadowing at LHC
Single hadron suppression at LHC
Dihadron suppression at LHC
Dihadron suppression at LHC
A roadmap for jet study at LHC
Re-constructed jets open up a whole new world for jet quenching study
(I always believe what my experimental colleagues tell me)
Reconstructed jets:
(1) Single inclusive jets
(2) Di-jets
(3) Gamma-jets
(1) Measurements of jet shape
• RAA(ET) for jets: 1
Jet cone size R
RAA
For single hadrons
(2) Direct measurement of qhat
2 ˆ( , )T q Edy yq
J. Casalderrey-Solana and XNW, arXiv:0705.1352 [hep-ph].
33ˆ2 ( )
T
s q T
Majumder, Muller and XNW, arXiv:hep-ph/0703082
q-hat in a nucleus
2ˆ 0.01 GeV /Fq fm
20ˆ 1.0 GeV / ( =1 fm)Fq fm
e-
E. Wang & XNW PRL 89, 162301(2002)
(3) Modified fragmentation functions
XNW, Huang and Sarcevic, Phys.Rev. Lett. 77, 231 (1996)
Utopia?