The “Ridge” & “Cone”Theoretical model expectations2- and 3-particle correlation results
Reaction plane dependenceRidge and Cone
Summary
Di-hadron and three-particle correlations at RHIC
Pawan Kumar Netrakanti Nuclear Physics Division
B.A.R.C., Mumbai
Outline
WPCF-2011September 20th -24th, Tokyo
“Ridge” : Near-side correlations
Near-side “ridge” in central Au+Au collisions. Properties similar to bulkExtends even upto higher rapidities. Long range correlations.Ridge persists to very high pT trigger particle
d+Au Au+Au0-12%
QM09
pTTrig > 4 GeV/c
2<pTAssoc<pT
Trig GeV/cPhys. Rev. C 80 (2009) 064912.
04/21/232
“Ridge” : Theoretical model expectations
3
1)In medium radiation + longitudinal flow pushN.Armesto et.al Phys.Rev.Lett.93(2004) 242301
2)Turbulent color fields A.Majumder et.alPhys. Rev. Lett.99(2004)042301
4) Momentum Kick C.Y. Wong hep-ph:0712.3282
3) Recombination between thermal and shower partonsR.C. Hwa & C.B. Chiu Phys. Rev. C 72 (2005) 034903
5) Transverse flow boostS.A.Voloshin, Phys.Lett.B. 632(2006)490E.Shuryak, hep-ph:0706.3531
6) Glasma Flux tubeA. Dumitru et. al Nucl. Phys. A 810, 91 (2008)K. Dusling et. al Nucl. Phys. A 828, 161 (2009)
Can we distinguish between these physics interpretations? 3-particle correlation in
Jet
Ridge
TriggerAssoc.
????
????
STAR 3-particleAcceptance
04/21/23
“Cone” : Away-side correlations
4
Away-side structure in 2-particlecorrelations in central collisions.
Conical emission is a possibleexplanation for shape:
Mach-cone shock waves Čerenkov gluon radiation
Other explanations suggested: Large angle gluon radiation Deflected jets
deflected by radial flowpath-length dependent energy
loss Odd harmonics (v3 ,v5 …….)
STAR PRL 95 152301 PHENIX
PRL 97 052301
Au+Au
0 /2
04/21/23
Study di-hadron triggeredcorrelations as a function of event plane angle ()
s = |t - | ~0o : In-planes = |t - | ~90o: Out-of-plane
Path length dependence of energy loss
3-particle correlations in azimuthalangle
Di-hadron correlations w.r.t EP
04/21/235
in-plane S~0 out-of-plane S~90o
||<1
Background : Mixed events (v2)
Au+Aud+Au
||>0.7
||<0.7
arXiv : 1010.0690
STAR Preliminary
STAR Preliminary
Estimate of triangular flow
6
Using FTPC v2 (2.5 < || < 4.0)
Using Fourier v2{2,|>0.7}
• The above results represent the v2{2} and v4{2}=1.15v22 subtracted
signal.• Blue/green curves represent estimated/measured v3{2}.• Remainder v4{2-uncorr}:
2 24 2 4 4 2{ -uncorr} {2} { }v v v
STAR Preliminary
ZYAM background normalization
arXiv : 1010.0690
V3 2 / v
2 2=0
.1
vn subtracted di-hadron correlations
04/21/237
v3 flow background v4{uncorr} background
1/N
trigdN
/dΔ
φ
STAR PreliminarySTAR Preliminary
• Black: v2{2} and v4{2}=1.15v22 subtracted signal.
• Red : v3{2} and v4{2-uncorr} subtracted signal.• Results qualitatively consistent; near-side ridge slightly
reduced due to vn.
Au+Au 20-60%, pTtrig=3-4 GeV/c, pT
assoc=1-2 GeV/c, large ||>0.7, ZYAM background.
vn subtr. dihadron correl. w.r.t. 2 and 3
Dihadron correlation broadens from in- to out-of-plane in 2
while narrows in 3
1/N
trigdN
/dΔ
φ
8
STAR Preliminary
2 in-plane
2 out-plane
3 in-plane
3 out-plane
STAR Preliminary
Simple background normalization: <signal> = 0.
Au+Au 20-60%, pTtrig=3-4 GeV/c, pT
assoc=1-1.5 GeV/c, large ||>0.7
Three-particle - correlations
9
pp
Au+Au 80-50%
Au+Au 0-12%
Phys. Rev. Lett. 102 (2009) 52302
d+Au
Au+Au 50-30%
Au+Au 30-10%
3<pTTrig<4 GeV/c
1<pTAssoc<2GeV/c
04/21/23 Have to estimate the vn effects….and working on it
Projections and angle
10
No significant pT dependence of observed emission angle.Consistent with Mach-coneInconsistent with simple Čerenkov radiation
Au+Au 0-12%d+Au
Phys. Rev. Lett. 102 (2009) 52302
-0.07
0-12% Au+Au shows significantpeaks in off-diagonal projections at:1.370.02(stat.) +0.06 (sys.)radians.
Black: reaction plane frame 3-particle cummulant.
3<pTTrig<4 GeV/c
1<pTAssoc<2GeV/c
04/21/23
Three-particle - correlations
11
3<pTtrig<10 GeV/c 1<pT
assoc<3 GeV/c ||<0.7
Same-sign triplets (AAT)Ridge : 4* AAT
Like-sign triplets : Dominated by ridge
Same-sign associated pair and opposite sign trigger particle (AAT )
Jet-like: Total - Ridge
Phys. Rev. Lett. 105, 022301 (2010)
04/21/23
<Pjr>
<Pjr>
<Pjr>
<Pjr>
Average pair densities
12
3<pTtrig<10 GeV/c
1<pTassoc<3 GeV/c
||<0.7
Jet-like
<Pjr> : -0.004 0.025
<Pjj> : 0.077 0.026<Prr> : 0.114 0.039
Jet-ridge cross pairs
Ridge production appears to be uncorrelated with the presence of jet.
Ridge
Au+Au 0-12%
<Prr>
<Prr>
<Pjj>
Phys. Rev. Lett. 105, 022301 (2010)
04/21/23
Radial and angular dependence
13Ridge is broad. No prominent substructures in ridge.
R
-/2
+/2
Phys. Rev. Lett. 105, 022301 (2010)
04/21/23
Data and models
14
1)In medium radiation + longitudinal flow push
Model : Diagonal excess Data: Uniform
2)Turbulent color fields
5) Transverse flow boost 6) Glasma Flux tube
Data:Uniform. No jet-ridge cross pairs
Data : <Pjr> ~ 04) Momentum Kick 3) Recombination Model
Data:Broad Ridge, no jet-ridge cross pairs
Model: jet-ridge cross pairs. Model : Jet-ridge cross pairs
Model: Uniform, Jet-ridge cross pairs Model: Uniform. Jet-ridge cross pairs ????
Data:Uniform. No jet-ridge cross term
Model: uniform ridge, jet-ridge cross pairs.
Data <Pjr> ~ 0
????
????
04/21/23
Evolution of double peak structure from in-plane to out-of-plane Dihadron correlations w.r.t. 2 and 3 may indicate path-length/geometry effects Physics mechanism still under debate.
Summary
15Thank you
Jet and Ridge are “separated” by using the charge dependence. Ridge broad and uniform, jet narrow in . Ridge production appears to be uncorrelated to the presence of the jet. Ridge may have the path length dependence.
“Ridge”
“Cone”
Study of correlation of particles has improved the understanding of the heavy-ion collisions.
04/21/23
Back up
04/21/2316
Triangular flow
Odd harmonics may not be neglected.
ALICE, PRL 107, 032301 (2011)
17
Alver, Roland, PRC 81, 054905 (2010)
dN/d = 1 + 2v22cos(2) + 2v3
2cos(3) + 2v42cos(4)….
“Cone” : Theoretical model expectations
18Away-side
Mach Cone :• Mach angle depends on speed of sound
in medium • T dependent
• Angle independent of associated pT.
cvp
c partons
;2
M
parton
s
v
c cos
Trigger
MM
PNJL Model
Cerenkov gluon radiation : Gluons radiated by superluminal partons. Angle is dependent on emitted momentum.
)(
1
)(cos
pnvpn
c
v
c
partonc
parton
n Čerenkov angle vs emitted particle momentumI.M. Dremin (Nucl. Phys. A750: 233, 2006)
V. Koch et. al. (Phys. ReV. Lett. 96, 172302, 2006)
Can we distinguish between these physics interpretations? 3-particle correlation in
Medium
away
near
di-jets
2-particle correlation 3-particle correlation
Mediumaway
near
deflected jets
away
near
Medium
Conical Emission
vn subtracted dihadron Correlations(pT
trig=3-4 GeV/c, pTassoc=1-2 GeV/c, large ||>1)
Remark: Associated pT range ~ pTref. Case of data-data=0: jet-correl nonflow is
subtracted; what’s left are similar between centralities, and resemble a v1 component.
19
Au+Au80-50%
50-20% ZDC 12%
pTref=0.2-5 GeV/c
ALICE, PRL 107 (2011)
STAR Preliminary STAR Preliminary STAR Preliminary
Simple background normalization: average signal = 0.
vn subtracted dihadron correlations(pT
trig=3-6 GeV/c, pTassoc=2-3 GeV/c, ||>1)
Bkgd subtracted using two-particle vn{2} (flow+fluctuation). vn{4} may not be very relevant: fluctuation effect is negative; v3{4}~0. Near-side ridge in central collisions seems still visible. Ridge may be not
entirely due to vn. Away-side is suppressed at high-pT in central collisions. Shape modification at
intermediate-low pT. Residual non-flow should be present in the measured vn. Important next step is
to separate non-flow contribution.20
80-50%50-20% ZDC 12%
STAR Preliminary STAR Preliminary STAR Preliminary
Simple background normalization: <signal> = 0.
04/21/2321
Hydro, Boltzmann calculations: J. –Y. Ollitrault
STAR: Aihong Tang, Proc.24th Winter Workshop on Nuclear Dynamics