Transcript 3 Particle Correlations

Jet correlation measurements
from RHIC/STAR
Fuqiang Wang
The Idea
well calibrated: can be
calculated
Au+Au by pQCD.
hadrons
p+p
leading
particle
hadrons
q
q
q
q
q q
hadrons
leading particle
•
•
di-jet, back-to-back.
well calibrated – pQCD.
Fuqiang Wang, USTC workshop, July 2008
• embed di-jet in AA
• interact with the medium
• probe medium properties
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Single hadron suppressed
AA over binary-scaled pp
High-pt mostly from jets.
x5
Strong jet-quenching
Fuqiang Wang, USTC workshop, July 2008
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Dihadron better sensitivity
Di-hadron
Single
y (fm)
y (fm)
x (fm)
Less surface bias
T. Renk, PRC 74 (2006) 034906
T. Renk and Eskola,hep-ph/0610059
x (fm)
dihadron
single hadron
H. Zhang et al., PRL 97 (2006) 252001
Fuqiang Wang, USTC workshop, July 2008
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Dihadron suppressed
pTtrig>4 GeV/c, 2<pTassoc<4 GeV/c
Fuqiang Wang, USTC workshop, July 2008
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Occasionally they do come out
STAR, PRL 97 (2006) 162301.
Fuqiang Wang, USTC workshop, July 2008
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Detour: if trigger on the di-jet…
3
STAR Preliminary
Au+Au
d+Au
T2A1_T1
2
1
STAR Preliminary
0.5
0
0
-2
Au+Au
12% central
|Df |<0.7
1.0 T1A1_T2
1
_dN_
Ntrig d(Dh )
1
_dN_
Ntrig d(Df )
Trigger 1: pT>5 GeV/c, Trigger 2: pT>4 GeV/c, Assoc: pT>1.5 GeV/c
STAR Preliminary
-1
0
1
2
Df
3
4
5
No modification from d+Au to Au+Au
-1.5
-1
-0.5
0
Dh
0.5
1
1.5
no ridge
No energy loss for triggered di-jets!
Tangential di-jets (or punch-through without interactions).
Fuqiang Wang, USTC workshop, July 2008
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Energy is not lost
STAR, PRL95 (2005) 152301
pTtrig=4-6 GeV/c, pTassoc=0.15-4 GeV/c
PRL95 (2005) 152301
Low pT
Broader, softer.
Fuqiang Wang, USTC workshop, July 2008
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Energy shows up in a strange way
near
near
pTtrig=3-4 GeV/c, pTassoc=1-2.5 GeV/c
M. Horner, QM06.
double peaked
away
deflected jets
away
near
away
mach cone
Fuqiang Wang, USTC workshop, July 2008
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3-particle correlation
d+Au
Au+Au 0-12%
near
away
Evidence of
Conical
emission
1.38 ± 0.02 (stat.)
± 0.06 (syst.)
Fuqiang Wang, USTC workshop, July 2008
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Why is it important?
length x 1016
time x 1022
Casalderrey-Solana, Shuryak, Teaney, hep-ph/0411315
Mach cone angle qM 
speed of sound cS = sin(qM)
equation of state
Fuqiang Wang, USTC workshop, July 2008
qM
v > cS
zone of
action
2
1
0
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dE/dx model, pQCD, N=4 SYM
Renk, Ruppert,
PRC 76, 014908
(2007)
r
x  ( x)
2
mD T
r
x gz ( x)
mD2 T
Neufeld, Muller,
Ruppert
u = 0.99955 c
Chesler & Yaffe
arXiv:0712.0050
u = 0.75 c
Fuqiang Wang, USTC workshop, July 2008
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The near-side ridge
STAR, PRL95 (2005) 152301.
Au+Au
ridge
d+Au
Fuqiang Wang, USTC workshop, July 2008
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Extend to very forward rapidity
Trigger: 3<pTtrig<4 GeV/c, 0.2<pTassoc< 2 GeV/c
d+Au MB
Au+Au central
PHOBOS preliminary

Away-side very similar.

Ridge extends to very
forward rapidity.
Fuqiang Wang, USTC workshop, July 2008
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What is the ridge?
In medium radiation +
Longitudinal flow push
N.Armesto et.al
PRL 93 (2004) 242301
Turbulent color fields
A.Majumder et.al
PRL 99 (2004) 042301
Fuqiang Wang, USTC workshop, July 2008
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3-particle correlation in Dh-Dh
3<pTTrig<10 GeV/c, 1<pTAsso<3 GeV/c, |Df|<0.7
dAu
AuAu 40-80%
AuAu 0-12%
STAR Preliminary
 The ridge is uniform
in every event.
 No significant
structures along
diagonals or axes.
Fuqiang Wang, USTC workshop, July 2008
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Near-side: jet + ridge
Aoqi Feng, CCNU
Au+Au 20-60%
STAR Preliminary
Away-side
in-plane fS=0
out-of-plane fS=90o
|Dh|<0.7 – |Dh|>0.7
Jet
|Dh|>0.7
Ridge
3<pTtrig<4, 1.5<pTtrig<2.0 GeV/c
Increasing away-side pathlength  increasing modification
Fuqiang Wang, USTC workshop, July 2008
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Ridge dominant only in-plane
Aoqi Feng, CCNU
out-of-plane
3<pTtrig<4, 1.5<pTtrig<2.0
GeV/c
STAR Preliminary
jet
20-60%
ridge
v2{4}
in-plane
STAR Preliminary
Jet consistent with d+Au.
v2{RP}
Ridge drops with trigger angle from RP.
Strong near-side jet-medium interaction in reaction plane
 large ridge.
Minimal near-side interaction perpendicular to reaction plane.
Fuqiang Wang, USTC workshop, July 2008
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Summary
• Strong jet quenching.
• Strong medium modification to jet
correlation.
• Evidence of conical emission –
Mach-cone shock wave.
• Ridge not well understood yet –
new results to come.
Fuqiang Wang, USTC workshop, July 2008
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