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