Jet Correlations

Jet CorrelationsJet Correlations

Mike Miller (Yale University)Mike Miller (Yale University)

2Mike Miller January 2004

In QCD Medium Additional kT

Significant energy loss? high pT suppression

Sensitive to color Sensitive to color properties of mediumproperties of medium

“So, why jets?”

coneRWhy Jets?

Hard probeearly time Calculable: pQCD Abundant at RHIC, LHC

kT: “Radiative Corrections”

pre- and post-scattering di-jet:

Fragmentation:

z hadron

parton

p

p


Moment Analysis of QCD MatterconeR 2 ( )

( )

T g

g

k x dx

E x x dx

I. Vitev, nucl-th/0308028

Induced Gluon Radiation ~collinear gluons in cone “Softened” fragmentation

in je

i j t

t

n e

: increases

z : decreases

chn

Gyulassy et al., nucl-th/0302077

Fragmentation:

z hadron

parton

p

p


Partonic vs. Hadronic MechanismsHottest Questions:

Fragment inside/outside of medium?

Partonic vs. hadronic model of Final State interaction?

coneR

A Better Question: To what degree do partonic

and hadronic interactions contribute to quenching?

Discussion only recently started!

Fragmentation:

z hadron

parton

p

p


4 Ways to “Skin a Cat Jet”

1) Integral Distributions:<pT>, <Nch>

2) Single Particle Spectra:d/dpT RAA, RdA

3) 2-Particle Correlations:dN/d()

4) Jet Reconstruction:d/dET, Frag. Func.

trigger

“Trigger” = 0

Adler et al., PRL90:082302 (2003), STAR

near-side

away-side


, 200 GeVNNAu Au s

Disappearance of the away-sideDisappearance (at mid-rapidity) is dominated Disappearance (at mid-rapidity) is dominated by final state effect(s)!by final state effect(s)! Jet Quenching Jet Quenching

Adams et al., Phys. Rev. Let. 91 (2003)Adler et al., PRL90:082302 (2003), STAR

1/N

trig

gerd

N/d

()

Background subtracted

2nd order correlations due to elliptic flow of entire eventcompeting background

p+p2-jets

Peripheral Au+Au2-jets

Central Au+Au? 1-jet!1-jet!

Near side jet “identical” ppdAuAuAu

d+Au2-jets

di-hadron


Questions Raised at QM02

Initial state effects?

What should 2-particle correlation look like?

Partonic/nuclear kT

jT

Measurable at SPS?

Final state energy loss?

Baryons vs. Mesons?

PID?

Background subtraction?

Jets correlated with reaction plane?

And many more…

This talkThis talk Discussed in parallelDiscussed in parallel


Suppression larger out-of-plane

Path Length Dependence

nGLVE L

di-hadron, 20-60% Central Background SubtractedSee J. Bielcikova et al., (nucl-ex/0311007) for background derivation

STAR Preliminary

s =200 GeVNN

Measured

Reflected

K. Filimonov DNP03

In-plane

Out-of-plane


2.5 4 GeV/c

1 2.5 GeV/c

trigT

assocT

p

p


nGLVE L

Quenching: Consistent with path length DependenceQuenching: Consistent with path length Dependence


In-plane

Out-of-plane


hadron

hadron

Δφ

Jet Fragmentation: “Shape”

Reconstructed jets

sinhadronT T jet hadj p

-sinjetT T jet jetk p

di-hadron

2 2Fa

TTy Near r

pk

z

sin Nearyj p

Jet “width”

Jet-coplanarity

: of colliding

partons

a b

Ty T Tk p p��Tk

: of hadron to jet axis

Ty Tj p

Tj

parton

parton


kT, jT at RHIC from p+p Data

J. Rak, Wed.

J. Rak, DNP03

s=200 GeV

di-hadron

Statistical Errors Only

near-side away-side

nearfar


kT, jT at RHIC from p+p DataStatistical Errors Only

PHENIX preliminary

|jTy| = 35911 MeV/c

|kTy| = 96449 MeV/c

PHENIX preliminary

|jTy| = 35911 MeV/c

|kTy| = 96449 MeV/c

kT, jT from p+p, d+Au, Au+Au from “0”-hadron, di-hadron, jet, di-jet

Friday:Friday: Completing the reference measurements!Completing the reference measurements!

J. Rak, DNP03

s=200 GeV

Good agreement with previous measurements: PLB97 (1980)163 PRD 59 (1999) 074007

di-hadron

0

p+pd+Au

di-jet

STAR PreliminaryT. Henry, Fri.

10 GeVjetTE


s =200 GeV, Au+AuNN di-hadron correlations

<|jTy|>=400 MeV

-n

ear

-nea

rAu+Au near-side: Jet-like at all centralities?

Follows fragmentation prediction:

1sinTy

T

j

p

Yes, but… widens in

(see c07)


Quenching at SPS?charged-pion pairs

pT>1.2 GeV/c

, 158 A GeV/cPb Au

Accepted by PRL, nucl-ex/0303014, CERES

Near angle correlations:Near angle correlations: Present at all centralitiesConsistent with fragmentation

Away side correlations:Away side correlations:Present at all centralitiesWidth broadens with centrality

mid-central

central

width yield

+ WA98 Spectra: R+ WA98 Spectra: RAAAA>1 >1

See See p36p36

No, but…No, but…Broadening at RHIC!Broadening at RHIC!


Quenching at SPS?

Where is the enhancement at RHIC?Where is the enhancement at RHIC?


Di-Hadrons at “all” pT

See F. Wang, Fri. QM04

< 0.15 < GeV/c assoc trigT Tp p

+ mixed event background subtraction

+ elliptic flow background subtraction

Study “fragmentation” in p+p, Au+AuFull range in pT

Transport from high-pT to low-pT?Change in jet “size”?

Study Study ppTT distribution in near- distribution in near-

and away-side jet conesand away-side jet cones

di-hadron correlations4 6 GeV/ctrig

Tp

1.1


Di-Hadrons at “all” pT

Near-Side Away-Side

s =200 GeVNN

F. Wang, DNP03

0 1 2 3 4(GeV/c)Tp

0 1 2 3 4

STAR Preliminaryp+p40-80% Au+Au0-5% Au+Au

di-hadron correlations

See F. Wang Friday

4 6 GeV/ctrigTp


pT Distribution in Near-Side Jet

Near-Side

s =200 GeVNN

Au

Au

/pp

0 1 2 3 4(GeV/c)Tp

0 1 2 3 4

F. Wang, DNP03

STAR Preliminary

ratio

p+p40-80% Au+Au0-5% Au+Au


Near-SideNear-Side0-5% / pp 0-5% / pp 2 2

40-80% / pp 40-80% / pp 1.2 1.2““enhancementenhancement””

See F. Wang Friday

4 6 GeV/ctrigTp


pT Distribution in Away-Side Jet

Near-Side Away-Side

s =200 GeVNN

Au

Au

/pp

0 1 2 3 4(GeV/c)Tp

0 1 2 3 4

F. Wang, DNP03

ratio ratio

STAR Preliminaryp+p40-80% Au+Au0-5% Au+Au

See F. Wang Friday


suppressed

enhanced

Away-Side (Away-Side (ppTT>2)>2)

AuAu/pp <1AuAu/pp <1““Disappearance”Disappearance”

Away-Side (Away-Side (ppTT<2)<2)

AuAu/pp >1AuAu/pp >1““Enhancement!Enhancement!””

Near-SideNear-Side0-5% / pp 0-5% / pp 2 2

40-80% / pp 40-80% / pp 1.2 1.2““enhancementenhancement””

4 6 GeV/ctrigTp


Au+Au 0-5%

(1/N

trig)

dN/d

()

STAR Preliminary

p+p trig4 6 GeV/c

0.2 4 GeV/c

T

assocT

p

p

Background subtracted Background subtracted

Away-side looks jet-like in p+p, not central Au+Au!Away-side looks jet-like in p+p, not central Au+Au!

So what’s going on?So what’s going on?

Is The Away-Side Jet-Like?

See F. Wang Friday


Is The Away-Side Jet-Like?

Au+Au 0-5%

(1/N

trig)

dN/d

()

STAR Preliminary

p+p

Fit to near side: const. + gaussian + Borghini-cos(fixed)trig4 6 GeV/c

0.2 4 GeV/c

T

assocT

p

p

Background subtracted Background subtractedstat. mom.conserv.stat. mom. conserv.

free fit

2 21 2, cosmeasuredT

total

C p p dpN

N

��

1~ 10

Amplitude:Amplitude: -Depends on -Depends on ppTT “window” “window”

-Can be tested-Can be tested-Work in progress-Work in progress(see )(see )

Momentum conservation: 1 22 1 2 2

cos, 2 T T

total T

p pC p p

N p

��Borghini et al., nucl-th/0004026

See F. Wang Friday


What could this mean?

Au+Au 0-5%

(1/N

trig)

dN/d

()

STAR Preliminary

p+p

Fit to near side: const. + gaussian + Borghini-cos(fixed)trig4 6 GeV/c

0.2 4 GeV/c

T

assocT

p

p

Background subtracted Background subtractedstat. mom.conserv.stat. mom. conserv.

free fit

Pessimist:Pessimist:A fundamentally boring A fundamentally boring result…result…AnotherAnother background background

Optimist:Optimist:Maybe the most exciting Maybe the most exciting result yet!result yet!

Away-side energy re-distributed over many particles, broad in Away-side energy re-distributed over many particles, broad in angle, angle, but it is still there!but it is still there!

See F. Wang Friday


Conclusions2-particle correlations

Successful measure of hard-scattering, fragmentation

Away-side quenching in central Au+AuIndicative of strong final state interactionsIn/out-of plane consistent with path length dependence

Semi-hard scattering at SPSPresent at all centralitiesLarge away-side broadening

Near-side correlations in Au+AuConsistent with fragmentation at all centralities

pT distribution in near- and away-side jet conesConsistent with modified fragmentation?


The Real Conclusions

2-particle correlationsRobust jet probe from p+p to central Au+Au

QM02Disappearance of away-side jet

QM04Finding the “lost-energy” on the away-side

Qualitative consistency between PHENIX and STAR

“Transport” from high pT low pT

But… away-side has lost jet-like shape!


Future Directions at RHIC

Minimize ambiguities, sensitivitiesHigher trigger pT only jet production

higher trigger pT smaller kT effects

Higher statistics test of path length dependence

Away-side pT “transport”d+Au?

Trigger-pT dependence?Punch through above momentum conservation?

Calibrate the jet-energy scale: photon-jetMass effect: heavy quarks vs. light quarks EColor charge: quark vs. gluon jets?


Old…


Back side correlations between charged hadrons:Back side correlations between charged hadrons:1/N

trigger*dN/d(∆Φ)

1/N

trigger*dN/d(∆Φ)

1/N

trigger*dN/d(∆Φ)

1/N

trigger*dN/d(∆Φ)

∆Φ (radians)

∆Φ (radians)∆Φ (radians)

∆Φ (radians)

3.7 GeV < P3.7 GeV < PT T trigger trigger <4.5 GeV<4.5 GeV

2.5 GeV < P2.5 GeV < PT T associated associated <3.7 GeV<3.7 GeV



6.5 GeV < P6.5 GeV < PT T trigger trigger <10 GeV<10 GeV




Fig. 11 Charged Hadrons correlations for different trigger PFig. 11 Charged Hadrons correlations for different trigger PTT rangerange

Fig. 12 Same side and back Fig. 12 Same side and back side as function of Trigger Pside as function of Trigger PTT

same side is calculated by integrating the Gaussian component and the back side is calculated by integrated the cosine component. Notices that there is a back side signal for the higher PT correlation

Trigger PT

)cos(2

)( cos2

)(

1

2

2

C

BGeCD

Fitting Function:

Trigger PT

In Fig.13. The fitting Ccos is compared to estimation due to the momentum conservation[6].

Fig. 13Fig. 13


In-plane

Out-of-plane


nGLVE L

Quenching: Consistent with path length Dependence!Quenching: Consistent with path length Dependence!



STAR Preliminary

s =200 GeVNN

Measured

Reflected

K. Filimonov DNP03


In-plane

Out-of-plane


nGLVE L

Quenching: Consistent with path length Dependence!Quenching: Consistent with path length Dependence!



STAR Preliminary

s =200 GeVNN

Measured

Reflected

K. Filimonov DNP03


Away-Side Quenching (2002)



, 200 GeVNNAu Au s 2nd order correlations due to elliptic flow of entire eventcompeting background

1/N

trig

gerd

N/d

()p+p

2-jetsPeripheral Au+Au

2-jetsCentral Au+Au

? 1-jet!1-jet!

di-hadron


Away-Side Quenching (2002)



, 200 GeVNNAu Au s 2nd order correlations due to elliptic flow of entire eventcompeting background

1/N

trig

gerd

N/d

()p+p

2-jetsPeripheral Au+Au

2-jetsCentral Au+Au

? 1-jet!1-jet!

di-hadron


Conclusions2-particle correlations

Successful measure of hard-scattering, fragmentation

Jet-like correlations at all centralities in Au+Au

Away-side correlationspT distribution in near- and away-side jet cones

Consistent with modified fragmentation?


Unraveling final state mechanisms at RHIC

Minimize ambiguities, sensitivitiesHigher trigger pT only jet production

higher trigger pT smaller kT effects

Higher statistics test of path length dependence

Away-side pT “transport”d+Au?

Trigger-pT dependence?Punch through above momentum conservation?

Calibrate the jet-energy scale: photon-jetMass effect: heavy quarks vs. light quarks EColor charge: quark vs. gluon jets?

Documents

Jet Correlations