Cone is medium response, Ridge is medium itself.

Cone is medium response, Ridge is medium itself.

Fuqiang WangPurdue University

For the STAR Collaboration

Plan of talk

• Away-side cone: medium response to hard probes

• Near-side ridge: medium response or itself?

Bridger ridge, Montana

2Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

The away-side structure

3

p+p

Au+Au

Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

PHENIX

Df

High pTtrigger particle

associatedparticles Away-

side

triggerjet

0 p1-1 Df

Possible physics scenariospT

trig=3-4 GeV/c, pTassoc=1-2.5 GeV/c

Away-side

triggerjet

0 p1-1 Df

trigger jet

Mach coneaway

away

trigger jet

deflected jets away

event1

event2

Surface bias


Df1= f1-ftrig

Df2

p

p0

0

= f2-ftrig

3-particle azimuthal correlation

Df1

Df2

p0

0

p

away

trigger jet

deflected jets away

event1

event2

trigger jet

Mach cone

away away

signature of conicalemission


Evidence of conical emission

d+Au Au+Au central

Df1

Df2

p00

p

Away-side

STAR, PRL 102, 052302 (2009)

trigger


Conical emission angle

q = 1.37 ± 0.02 (stat.) ± 0.06 (syst.)

STAR, PRL 102, 052302 (2009)

Away-side

trigger

q

Constant cone angle vs pT suggests Mach Cone shock waves may be the underlying mechanism.


Higher trigger pT

4 < pTtrig < 6 GeV/c

1 < pTassoc < 2.5 GeV/c

6 < pTtrig < 10 GeV/c

1 < pTassoc < 2.5 GeV/c

1 < pTassoc < 2 GeV/c


Theory calculations

Parton energy loss:Renk et al. PRC 76, 014908 (2007)

pQCD + hydro:Neufeld et al.arXiv:0807.2996 quark v = 0.99955

(z -

ut)

x (rx)mD

2 T

x gz (rx)

mD2 T


AdS/CFT Correspondence

N = 4 Super-Yang-Millstheory in 4d with SU(NC)

Maldacena (1997), Gubser, Klebanov,Polyakov; Witten (1998)

YM observables at infinite NC and infinite coupling can be computed using classical gravity.

A string theory in 5d AdS

Measure heavy quark Mach-cone shock waves: Experimental consequence of string theory?

Chesler & Yaffe

arXiv:0712.0050

Heavy quark u = 0.75c


qM = 1.37

p

HGcS = 0.45

QGPcS = √1/3 = 0.58

Mixed phasecS = 0

Speed of sound?

cS far smaller than HG or QGP. Must have mixed phase (phase transition).

2 /Sc p EOS: p()

speed of soundcS ~ 0.2

However, model calculations indicate that Mach Cone angle can be altered by medium flow.


Investigating flow effect on cone angle

Fit to large Dh azimuthal correlations

2 Gaus: Ridge at 0 and ridge at p, same shape, diff. magnitudes2 Gaus: identical conical emission peaks symmetric about p.

STAR Preliminary


Au+Au 20-60%, 3<pTtrig<4, 1<pT

trig<2 GeV/c

• Cone angle takes off after trigger fs=45o.

• Split in pT after fs=45o.• Cone angle ~constant

over pT at fs<45o.

STAR Preliminary

STAR Preliminary


Is there a back-to-back RIDGE?

RP

Trig.

Ridge

Away 2

Away 1

Near Jet

Away-Side Ridge


Connection between near- and away-side

Away-side

0 p1-1 Df

STAR Preliminary


∆φ ∆φ ∆φ ∆φ ∆φ ∆φ

• Separate 1st and 2nd quadrants trigger particles• Azimuthal correlation for large |Dh|>0.7• Near-side ridge Gauss repeated at “+π”• Subtract back-to-back symmetric ridge peaks

∆φ ∆φ ∆φ ∆φ ∆φ ∆φ

STAR Preliminary


Away-side asymmetric cone positions

• Evidence of flow effect on conical emission.• Important to disentangle flow effect and conical emission angle.

1st cone peak

2nd Cone peak

φs

∆φ

STAR Preliminary

RP

trigger2nd Cone

1st cone


Df

trigger particlepT > 3 GeV/c

assoc. particlepT =1-2 GeV/c

d+Au

Au+Au ridge

Df Dh

The longitudinal ridge

h ~ 1h ~ 0

High-pT

trigger particle

Dh

associated particle

|Df|

<0.7

Bridger ridge, Montana


What’s already known about ridge

M. Daugherity (STAR), QM’08, J.Phys.G35:104090,2008

STAR, arXiv:0909.0191

• Ridge present in untriggered correlation.

• Ridge increases with centrality.• Ridge pt spectrum is a bit harder than bulk. • Ridge particle composition similar to bulk.

Ridge extended to very large DhPHOBOS, arXiv:0903.2811

STAR Preliminary

2.7<|Df|<3.9pT

assoc > 1.0 GeV/c

STAR, arXiv:nucl-ex/0701061


New insights from RP-dependent dihadron correlations

jet

ridge

Dh cut to “separate” jet and ridge

Dh

|∆η|>0.7 = ridge + away-sideJet = (|∆η|<0.7) – Accept.*(|∆η|>0.7)

assuming ridge is uniform in ∆η.Dh

Feng, QM’06. STAR Preliminary

Au+Au 20-60%, 3<pTtrig<4, 1.5<pT

trig<2.0 GeV/c

d+Au


Ridge decreases with RP

Ridge drops when trigger particle moves away from RP.

in-plane out-of-planetrigger |fs|

STAR Preliminary


A model prediction motivated by data

in-planejet flow alignedmore ridge

out-o

f-pla

neje

t flow

misa

ligne

dle

ss ri

dge

Chiu,Hwa, arXiv:0809.3018Correlated Emission Model (CEM)

Alignment of jet propagation and medium flow produces the ridge.

If correct, would produce measureable asymmetry in near-side ridge correlation peak.

Correlated Emission Model (CEM)


Remove away-side from large Dh correlation

RidgeJet

Konzer, QM’09. STAR Preliminary|∆η|>0.7

∆f=fassoc – ftrig

Trig. pt=3-4 GeV/c, assoc pt=1-1.5 GeV/c

φs = 0 to -15 -15 to -30 -30 to -45 -45 to -60 -60 to -75 -75 to -90

-1 0 1 π

0.05

0

Au-Au 20-60%

ZYAM

• Jet remains constant• Ridge Decreases

• Jet symmetric• Ridge asymmetric


Correlation Asymmetry

0 1 1 0

0 1 1 0

N NA

N Nf f

f f

-

-

-

in-plane

trigger pt=3-4 GeV/c

Jet

Ridge

|fs|= ftrig – ψRP out-of-plane

CEM model

Ridge: assoc pt=1-1.5 GeV/cRidge: assoc pt=1.5-2 GeV/cJet: assoc pt=1.5-2 GeV/c

STAR Preliminary

• Away-side is Asymmetric (not shown in plot).

• Jet is symmetric.

• Ridge is Asymmetric!

• Ridge may be due to jet-flow alignment.

v2 syst.


New insights from 3-particle Dh-Dh correlation

How does long Dh come about?

Many models on the market. |Df|<0.73<pT

trig<10 GeV/c, 1<pTassoc<3 GeV/c

d+Au Central Au+Au

Netrakanti, QM’09. arXiv:0907.4744STAR Preliminary

3-particle Dh-Dh correlations

N. Armesto et al., Phys. Rev. Lett. 93 (2004) 242301

Fuqiang Wang Nucleus-Nucleus 2009, August 2009 29

3<pTtrig<10 GeV/c

1<pTassoc<3 GeV/c

|Df|<0.7

3-particle Dh-Dh correlations

Charge independent (All)

AALike = (AALikeTLike + AALikeTUnlike)

AAUnlike = All - AALike

dAu AuAu 12%

STAR Preliminary

Netrakanti, QM’09. STAR Preliminary

Separate jet and ridgeJet has charge ordering ridge does not

ridge

Same-sign triplets: Only ridge, no jet.

jet

Netrakanti, QM’09. arXiv:0907.4744.STAR Preliminary

Ridge is structureless

No prominent subtructures in ridge. (jet) = 0.25 0.09 (ridge) = 1.53 0.41

Radial Projection Angular Projection

STAR Preliminary

Netrakanti, QM’09. arXiv:0907.4744. STAR Preliminary

Rx


Ridge-jet cross pairs

2

2

Assuming Poisson statistics:

(0.8 / ) 1.26 0.50

(0.3 / ) 2 (0.8 / ) (0.3 / ) 0.16 0.17 0.09 0.53, 0.08

x x x

y y x y zz yy z

-

33

0.190.31

0.130.27

0.060.04

From 3-particle - correlation:

N pairs 1.42

N ridge pairs 1.26

N jet pairs and jet-ridge pairs 0.16

h h-

-

-

D D

From 2-particle correlation:N assoc 1.1N ridge 0.8N jet-like 0.3

hD

Let fraction of events containing ridgefraction of events containing jetfraction of events containing both ridge and jet

xyz

0.050.11

0.150.20

0.050.04

With systematic errors:

0.50

0.53

0.08

x

y

z

-

-

-

Ridge and jet appear to be anti-correlated.

Netrakanti, QM’09. arXiv:0907.4744. STAR Preliminary

Fuqiang Wang

Experimental facts1) Ridge increases with centrality.2) Ridge spectrum a bit harder than bulk.3) Ridge particle composition similar to bulk.4) Ridge present in untriggered correlation.5) Ridge is mainly in-plane.6) Ridge is asymmetric in Df.7) Ridge is very wide.8) Ridge is random.9) No jet-ridge cross-talk.10) Ridge may be back-to-back.11) Ridge seems unrelated to jet.

Now let’s go to models…


In-medium rad. + long. Flow push

• Ridge increases with centrality.

• Ridge spectrum a bit harder than bulk.

• Ridge particle composition similar to bulk.


• Ridge is mainly in-plane.

• Ridge is asymmetric in Df.

• Ridge is very wide.

• Ridge is random.

• No jet-ridge cross-talk.

• Ridge may be back-to-back.

• Ridge seems unrelated to jet.

N. Armesto et al., Phys. Rev. Lett. 93 (2004) 242301

xx

x

x35Fuqiang Wang

Turbulent color field












A. Majumder et al., Phys. Rev. Lett. 99 (2004) 042301

x

x36Fuqiang Wang

Recombination of thermal+shower partons

37












R.C. Hwa, C.B. Chiu, Phys. Rev. C 72 (2005) 034903

x

x

x

Fuqiang Wang

Momentum kick model

38












C.Y. Wong hep-ph:0712.3282

xx

x

x

Fuqiang Wang

Transverse flow boost

39












S.A. Voloshin, Phys. Lett. B 632 (2006) 490; E. Shuryak, Phys. Rev. C 76 (2007) 047901

xFuqiang Wang

Glasma flux tube fluctuation + radial flow

40












R. Venugopalan et al., arXiv:0902.4435

ridgeridge

Fluctuation of color flux tubes excess ridge particles

(larger in-plane due to flow?)x

Fuqiang Wang

Summary and open questions• Conical emission of correlated particles.

Medium response to hard probes. Suggests Mach cone shock waves.– What distortion to Mach angle by medium? – How to extract speed of sound? EOS?

• Ridge is uniform in pseudo-rapidity.Likely medium itself at early time.– Is it due to color flux tubes?– What additional work to falsify this and other

models, or learn something from them?


Backups

v2 systematic uncertainties


On-diag projection

Off-diag projection

On-diag projection

Off-diag projection

Jet-like 3-p correlation RP-frame cumulant Lab-frame cumulant

3 1 2 3 1 2 2 1 2 1 2 1 1 2 2 2 1 1 1 1 1 1 2ˆ ( , , ) ( , , ) ( , ) ( ) ( , ) ( ) ( , ) ( ) 2 ( ) ( ) ( )t t t t t t - - -


Df

trigger particlepT > 3 GeV/c

assoc. particlepT =1-2 GeV/c

Large combinatorics

N jet particles ~ 1, N bkgd particles ~ 20

pTtrig=3-4 GeV/c, pT

assoc=1-2 GeV/c

Extremely difficult analysis. Careful subtraction of bkgd. Extensive assessment of systematics.

Combinatorial pair bkgd is huge!


What’s left on the away-side?

first peak

second peak

φs φs φs

Differential pathlength sensitivity

2

3

4

0 p/2

0.1

0.2

Peak position

Peak areaPeak

0.4

0.5

0.6

Peak distance


• Jet constant with fs.• Ridge decreases with fs.• Cone increases with fs.

• Jet decreases with pT.• Ridge constant with pT.• Cone decreases with pT.

STAR Preliminary

STAR Preliminary


Black : Raw signal

Pink : Mixed-event background

Blue : Scaled bkgd by ZYA1

Red : Raw signal – bkgd

2-particle correlationAuAu ZDC central (0-12%) triggered data, 3<pT

Trig<10 GeV/c, 1<pTAsso<3 GeV/c

Dh acceptance corrected

STAR Preliminary

|Df|<0.7

|Df|<0.7

Ridge


3-particle correlation background

Raw Raw Raw signal Raw Bkg Hard-Soft Bkg1 Bkg1 Bkg1 Bkg2

correlated

Soft-Soft

- -


Jet and Ridge contributions

AAlikeTlike : No JetOnly Ridge

Ridge (T- A+) A+) = Ridge (T+ A+) A+)Ridge (T+ A- ) A-) = Ridge (T- A- ) A-)Ridge (T+ A-) A+) = Ridge (T+ A+) A+)Ridge (T- A+ ) A-) = Ridge (T- A- ) A-)

Netrakanti, QM’09. STAR Preliminary


Cone is medium response, Ridge is medium itself.

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