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1Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Multi-hadron Multi-hadron correlations at RHIC correlations at RHIC and LHCand LHC
Olga Barannikova
2Olga Barannikova
University of Illinois at ChicagoLHC09, PragueLHC09, Prague
OutlineOutline
Jet quenching in heavy ion collisionsEvolution of jet-type correlation analysesTheoretical interpretation of data
Multi-hadron correlations at RHIC
Jets studies via correlations at LHC
Outlook
3Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Motivation: early resultsMotivation: early results
Signature two-particle correlation result: Disappearance of the away side jet
in central Au+Au collisions Effect vanishes in peripheral/d+Au
collisions
4<pT trig<6 GeV/c 2<pT assoc<pT trigPRL 91 (2003)
072304
PRL 91 (2003)
072303
High pT hadron suppression: Final state effect in Au+Au
collisions Observation extends to all accessible
pT range
4Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Motivation: higher pMotivation: higher pTT??
4<pT trig<6 GeV/c 2<pT assoc<pT trig
Recovering the away side:• Away-side yield suppression• Little modification of the Near-side yields • No broadening on Near- or Away-sides
d+Au
1/N
trig
dN
/d(
)
Au+Au 20-40% Au+Au 0-5%
8 < pTtrig < 15 GeV/c, pT
assoc>6 GeV/c
PRL 97 (2006) 162301
5Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
High-pHigh-pT T – – vacuum fragmentation?vacuum fragmentation?
Dh1h2 zT ,pTtrig pT
trig d AAh1h2 dpT
trigdpT
d AAh1 dpT
trig
zT pTassoc
pTtrig
Near >
PRL 97 (2006) 162301
Near-side: No dependence on zT in the
measured range – no modification Away side:
Suppression ~ level of RAA
No dependence on zT in the measured range – no modification
6Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Jet modifications: pJet modifications: pT T
One high-pT, one low-pT trigger Reappearance of the away-side jet Double-hump structure hints at additional
physics phenomena
3<pT trig<4 GeV/c 1.3<pT assoc<1.8GeV/c
M. v Leeuwen,
Hangzhou ‘06
PHENIX
PRL 97, 052301 (2006).
1.0 GeV/c < pT assoc
7Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Au+Au 0-10%STAR preliminary
Intermediate pIntermediate pT T : the ridge: the ridge
d+Au min. bias
STAR preliminary
3 < pT,trigger < 4 GeV/c
Near-side correlation structure: Central Au+Au: cone-like + ridge-like Strong dependence of cone yield on trigger pT
Week dependence if ridge yield on trigger pT
J. Putschke QM ‘06
8Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Energy Loss in QCD MediumEnergy Loss in QCD Medium
Double-hump Away-side Long-range Ridge on Same-side
Mach Cone Possible “splash back”
Parton mult. scattering, recombination Chiu, Hwa PRC72:034903,2005
– Radial flow + jet-quenchingS.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531
Parton + longitudinal flow coupling Armesto et.al PRL93(2004) 242301
…
Quantitative measures energy loss…
Mach ConeStoecker, Nucl. Phys. A750(2005)121Casalderrey-Solana, Shuryak, Teaney, J. Phys. 27(2005)22 Ruppert, B. Muller, PLB 618 (2005)123Renk, Ruppert, PRC 76 (2007) 014908
Parton mult. scattering, recombination Chiu, Hwa, PRC 74(2006) 064909
Radial flow boost + jet quenching Armesto, Salgado, Wiedemann, PRL 93 (2004) 242301
Parton + longitudinal flow coupling
…
9Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
d+Au
Au+Au central
Away side: Away side: -- correlation correlation
nucl-exp:0805.0622
Experimental observation of conical emission = 1.37 ± 0.02 (stat.)± 0.06 (syst.)
Constrains the speed of sound cS ~ 0.2
10Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Near-side: Near-side: -- correlations correlations
No acceptance
No acceptance
No apparent substructure – no gluon fragments/flow coupling?
No cross-like term – ridge and cone decoupled?
P. Netrakanti QM’08
3<pTTrig<10 GeV/c 1<pT
Asso<3 GeV/c
11Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Use di-jets to study jet-medium effects “pin” the jet axis selecting back-to-
back triggers study correlation w.r.t. this axis
2+1 Correlation Technique2+1 Correlation Technique
Courtesy of
R .Hollis
“jet-axis”
trigger (T2)
primary
trigger (T1)
associates
associates Raw, uncorrected signal
-1-2 0 1 2 3 4 5
a.u
.
0.6
0.4
0.2
T1: pT>5GeV/c
T2: pT>4GeV/c± 0.2
O.B., QM’08
12Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Olga BarannikovaUniversity of Illinois at Chicago
2+1 Signal Construction:2+1 Signal Construction:
Raw Correlation Background
Signal
0 - 10% 10-20%
20-30% 30-40%
Flow
T1: pT>5GeV/c
T2: pT>4GeV/c
A: pT>1.5GeV/c-1 0 1 2 3 4 5-2
0.5
0.51.0
1.0
0
STAR Preliminary
Away-side!
Phys. Rev. C72 (2005) 014904
O.B., QM’08
13Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Correlated Background:Correlated Background:
Signal + Background
Background
Signal
a.u
. T1T2
0 2 4
Accounting for correlated background on T1 and T2 side
Correlated background approximated by di-hadron correlations T2A1, T1A1
2+1 Correlation
-1-2 0 1 2 3 4 5
2
1
0 1
_d
N_
N
trig
d
)
STAR Preliminary
-1-2 0 1 2 3 4 5
2
0 1
_d
N_
Ntr
ig d
)
-2
4
STAR Preliminary
14Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Di-jets in d+Au 200 GeV Minimum bias data
Slight narrowing of the same-side, big effect for away-side
Difference in yields Di-triggers sample higher
energy jets
Di-jets in d+Au CollisionsDi-jets in d+Au Collisions
T2A1_T1
T2A1
-1-2 0 1 2 3 4 5
1
0
1
_d
N_
Ntr
ig d
) 2
STAR Preliminary
Single trigger
vs.Di-jet trigger
O.B., QM’08
15
LHC09, PragueOlga Barannikova
University of Illinois at Chicago
Di-Jets in Au+Au CollisionsDi-Jets in Au+Au Collisions
Au+Au
d+Au
-1-2 0 1 2 3 4 5
1
0
1
_d
N_
Ntr
ig d
)
STAR Preliminary
2
3
200 GeV Au+Au & d+Au
Central Au+Au ~ d+Au. No away-side suppression! Shapes of near- and away-sides are similar
projection: no significant shape/yield modifications projection: no apparent ridge
O.B., QM’08
Au+Au 12% central
||<0.7
T2A1_T1T1A1_T2
-1-1.5 0 1-0.5 0.5 1.5
1
_d
N_
Ntr
ig d
)
STAR Preliminary
0
200 GeV Au+Au
16Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Model PredictionsModel Predictions
<E> deposition for back-to-back jets
The energy deposition : T1 , T2 Tune the sensitivity of 2+1 correlations to any medium recoil
T. Rank
PRC75 (2007) 054910
17Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Monte Carlo studies for LHCMonte Carlo studies for LHC
Generator level study “Generic” HI detector:
Charge hadron tracker
full azimuthal coverage within ||<2.5
pTassoc> 2GeV/c
RHIC-based efficiency/v2
assumptions
10% central Pb+Pb 5.5TeV
HYDJET
Lokhtin et al,hep-ph:0810.2082
18Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
15<pTTrig<20 GeV/c
Mixed Event Background (ZYAM normalization)
Correlation studies with HydjetCorrelation studies with Hydjet
Can compare UNQUENCHED and QUENCHED mode
Raw Signal
a. u
.
HYDJET
Lokhtin et al,hep-ph:0810.2082
19Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Unquenched Hydjet
Jet yields and energy measurementsJet yields and energy measurements
Jet-energy measurements via associated hadrons
pT in the correlation peak
Jet-multiplicity measurementsSensitivity to quenching?
Lower pT?
V. Chetluru
QM’08
20Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
Summary &Outlook:Summary &Outlook: Medium-induced jet modifications
Double-hump away side Ridge
Differential studies are afforded by multi-particle correlation techniques 3particle - consistent with mach cone 3 particle - no substructure in ridge
Change fragmentation/surface bias with di-jet triggers 2+1 correlations – unmodified di-jet observation Au+Au ~d+Au
Potent tool for the LHC
4-7 February 2009
22Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
One high-pT trigger (only) Away-side modification
• Mono-jets?
• Energy loss for away-side jet?
Di-jet trigger No modification on away-side
• Surface dominated?
• No energy loss for di-jets?
Preliminary Results:Preliminary Results:
T1: pT>5GeV/c
T2: pT>4GeV/c
A: pT>1.5GeV/c
T2A1
T2A1_T1
-1-2 0 1 2 3 4 5
2
0 1
_d
N_
Ntr
ig d
)
-2
4
STAR Preliminary
23Olga Barannikova
University of Illinois at ChicagoLHC09, Prague
4-7 February 2009
STAR Preliminary **
Surface EffectsSurface Effects
T1: pT>5GeV/c
T2: pT>4GeV/c
A: pT>1.5GeV/c
If the triggers have tangential bias: expect a term related to the surface
Surface ~ R2 ~ Npart2/3
** Shown are statistical errors only
Number of triggers per event (per number of binary collisions)
Single triggers and (all qualified) pairs behave similar to inclusives
STAR Preliminary **
T1= 5 GeV/c
1000 200 300 Npart
0
N
trig__
Nev
t Np
art
2/3
0.4
d+Au
x10 -3
STAR Preliminary **
#T1T2 pairs / #Single triggers
#Di-Jets / #Single triggers
1000 200 300
0.015
0.05
0.01
Npart
24Olga Barannikova
University of Illinois at ChicagoLHC09, Prague 24
October 6-10, 2008
3-particle correlation in 3-particle correlation in A1A2
T : Trigger particleA1: First Associated particleA2: Second Associated particle
Jet fragmentation in vacuum
In medium radiation + Longitudinal flow
Transverse flow boost
N.Armesto et.al Phys.Rev.Lett.93(2004) 242301
S.A.Voloshin, Phys.Lett.B. 632(2006)490E.Shuryak, hep-ph:0706.3531
STAR TPC acceptance for3-particle correlation in (||<1 and full azimuth)
Turbulent color field. Momentum Kick C.Y. Wong hep-ph:0712.3282A.Majumder et.al
Phys. Rev. Lett.99(2004)042301