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A guide through pT landscale of di-hadron correlation

Jiangyong Jia Stony Brook University

EIC, 2007

and what can we learn about the partonic medi

um?

and what can we learn about the partonic medi

um?

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Should I worry about non-flow in correlation?

PHENIX: event plane measured at 3<|<4, tracks in ||<0.35Embed PYTHIA dijet into HIJING event to estimate the non-flow due to jets

•HIJING event is weighed with measured v2(pt,,b)•PYTHIA has 10 GeV dijet•Dijet->Biased Event plane->Fake v2 for trigger of the embedded jets. •Use away-side pp jet to approximate the ridge

Near jet

Away jetΦ

η

Ridge

Hijing+flow

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Should I worry about non-flow in correlation?

PHENIX: event plane measured at 3<|<4, tracks in ||<0.35Embed PYTHIA dijet into HIJING event to estimate the non-flow due to jets

•HIJING event is weighed with measured v2(pt,,b)•PYTHIA has 10 GeV dijet•Dijet->Biased Event plane->Fake v2 for trigger of the embedded jets. •Use away-side pp jet to approximate the ridge

3.04.00.42.8Fake v2

nucl-ex/0609009

Near jet

Away jetΦ

η

Ridge

Hijing+flow

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What v2 to use in correlation?

C() = (1+2<v2tv2

a>cos2) + J()

Non-flow due to jet is small with BBC Event plane

Other Non-flow and v2 fluctuations contribute to C(), so should be included in the two source model.

If minijets are important, then it should be much longer range in , or many minijets emitted in a correlated way?

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RAA

pT

1

Jet

Flow+coalescense

How the energy of the 80% jet redistributed to low pT? How to separate the Hard and Soft contribution down to low pT?

Production mechanisms: Jet (>5 GeV/c) and Flow+coalescense

0.2

Sources of single particles

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RAA

pT

1

Jet

Flow+coalescense

How the energy of the 80% jet redistributed to low pT? How to separate the Hard and Soft contribution down to low pT? Jet correlation: Energy dissipation to low pT

partonic stage: Jet energy couple with hydro-flow hadronization stage: Correlation affected by the coalescence process

Jet correlation provide constraints on the Geometrical bias

Production mechanisms: Jet (>5 GeV/c) and Flow+coalescense

0.2

Sources of single particles

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Sources of “jet” pairs Jet fragmentation contribution:

Near jet and away jet Medium-induced contributions:

Near-side Ridge, away-side Cone. Energy at low pT

How they evolve/compete in pT1 vs pT2 landscape?

Ridge

Cone

Near jet

Away jet

0

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High pT : Geometrical bias

IAA RAA, Why??STAR, Phys. Rev. Lett. 97 (2006) 162301

I AA

Transmission, Absorption shift

T. Renk notation

0.2

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PRC.71:034909,2005

Absorption picture always predicts IAA<RAA.

Need shift term!

High pT : Geometrical bias

IAA RAA, Why??STAR, Phys. Rev. Lett. 97 (2006) 162301

I AA

pT

RAA

Transmission, Absorption shift

T. Renk notation

0.2

Shift term is neededFor fixed RAA, a larger eloss required for a flatter spectra

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Energy shift0 spectra

n= 8.1 in dn/ptdpt

n=4.8 in dn/dpt for 5-10 GeV/c trigger

Per-trigger spectra

Away spectra flatter than single spectra

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Energy shift

0 spectran= 8.1 in dn/ptdpt

2( )

( ) 1n

TAA T

T

E pR p

p

8.1 2

1( )1 ( ) 0.23T

AA TT

E pR p

p

n=4.8 in dn/dpt for 5-10 GeV/c trigger

Per-trigger spectra

4.8 1

1( )1 ( ) 0.35T

AA TT

E pI p

p

• Bigger fractional eloss + flatter spectra --> Iaa ~ Raa• For -jet, IAA>RAA!• constrains the geometry bias by combing Iaa and Raa

nucl-ex/0410003

50% bigger

Away spectra flatter than single spectra

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Correlation landscape in pTA, pTB

Suppression in HR, enhancement in SR Peak location D independent of pT, jet reappearance not d

ue to merging of side peaks?

Dip grows

Jet emerges

arXiv:0705.3238 [nucl-ex]

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Correlation landscape in pTA, pTB

Head region: Suppression of jetShoulder Region: Response of the medium

pTA

pTB

Many possible routes! A single number summarizing the shape: RHS

Dip: RHS<1; Peak: RHS>1; flat: RHS=1 Jet shape symmetry :

RHS (pTA, pT

B) = RHS (pTB, pT

A)

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Awayside modification pattern vs pT

1<pTA,B < 4 -> RHS<1 -> Shoulder region dominant!

pTA,B >5 -> RHS>1 -> Head region dominant!

pTA,B < 1 -> RHS~1 -> SR feed in + radiated gluons?

arXiv:0705.3238 [nucl-ex]

Cone

Flat

Peakpt,1 pt,2>5

1<pt,1 pt,2<4

Competition between “Head” and “shoulder”.Suppression and enhancement

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Near side

Jet spectra shape: Near and Shoulder region

Near-side: flat with Npart (>100), increase with pTA.

Jet fragmentation S region: flat with Npart (>100) , independent of pT

A! Universal slope, reflects property of the medium?

Mean-pT at intermediate pT (1<pTB< 5) vs. Npart

arXiv:0705.3238 [nucl-ex]

2<pTA<3

3<pTA<4

4<pTA<5

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Near side Away shoulder

Jet spectra shape: Near and Shoulder region

Near-side: flat with Npart (>100), increase with pTA.

Jet fragmentation S region: flat with Npart (>100) , independent of pT

A! Universal slope, reflects property of the medium?

Mean-pT at intermediate pT (1<pTB< 5) vs. Npart

arXiv:0705.3238 [nucl-ex]

2<pTA<3

3<pTA<4

4<pTA<5

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Chemistry of Shoulder

Similar shape for asso Baryon and Meson

0-20%2.5-4x1.6-2 GeV/c

Jet frag.<Bayron/meson< bulk medium.

W. Holtzmann

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Chemistry of the Shoulder?

ud

uu

d

uud d

u

uud d

u

Bulk medium are boosted by shock wave, which then coalesce into hadrons? => jet frag.<Bayron/meson<Bulk

Coalescence plays a big role here.

Cooper-Fryer

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Parton-medium interaction

1) Radiative energy loss -> High pT suppression2) Lost energy converted into flow -> Intermediate pT enhancement3) Remaining propagate -> Gluon feedback at low pT

Propagation mode

Collective mode

Coupling with medium: Mach flow / deflection.

Deflected jet

Punch-through jet

Large angle radiation

Deflection: Deflection angle decrease with increasing pT?No enhancement in multiplicity?

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Radiation contribution

A. Polosa, C. Salgado, hep-ph/0607295, sudokov splitting

C. Salgado, U. Wiedemann, hep-ph/0310079

I. Vitev, gluon feedback

Can be large angle => But for hard jets, radiation almost collinear

Can explain multiplicity

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Near side: jet+ ridge

Near side Components

jet peak

Elongated ridge

3 < pt,trigger < 4 GeV

pt,assoc. > 2 GeV

Au-Au 0-10% STAR preliminary

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Near-side shape modification

Trigger pT =

2.5-4 x 2-3 GeV/c

width broadening limited to intermediate pT

Broaden at intermediate pTunmodified at high pT

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Modifications decrease with increasing trigger pT (flattening) Modification limited to pT

A,B 4 GeV/c, similar to the away-side Shoulder.

STAR: This is due to the Ridge.

Near-side yield modification: IAA

Jet

Ridge

Dilution effects due to soft triggers

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Intermediate pT : dilution effect

Jetpairs

JetpairsAA

AAcoll pp

JN

per-jet yield

Quantification via IAA is complicated when the trigger jet is modified.

per-trig yield

Dilutions effects Triggers have recombination contribution Boost from the radial flow? Trigger jet multiplicity is enhanced due to interaction with medium

AA AAT T

ppT

ppT

Jetpairs

JeN N

N

N

tpairs AA AA AA AA

AA

T T a a

coll pp

R I R IN

IAA reflects modification on Pairs √ and Triggers x AAAA

AA

JI

R

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Near side Iaa

We calculate the pair suppression factor, Jaa, from Iaa and Raa

RAA

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Near side Jaa

At high pT, both hadrons comes from same jet! The JAA represent the suppression on the jet (>pt1+pt2). Since Jet suppression is constant at high pT, Jaa should approach the constant RAA level at high pT!

Real enhancement is factor of 4-5 at low pT? (no suppression of jet pairs!) Imply intermediate pT single enhancement not due to jets?!

Leading hadron suppressionJet pair suppression

=

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Role of hadronization in correlation?

Bulk hadronization mechanisms can affect both the single (Thermal+Thermal Reco) and pairs (Thermal+Shower reco). Can it modify the correlation?

If so, how to isolate the pure partonic medium effect?

X.N. Wang et.al : in medium fragmentation

Parton-medium interaction

Hadronization via Coalescence

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Jet contribution at low pT? Once we map out the jet properties in pT1, pT2, can we combine c

orrelation results with single particle measurements and estimate the jet contribution or contribution initiated by jet, as function of pT.

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RAA

pT

1

Jet

Flow+coalescense

0.2

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We know the ratio of jet pair/combinatoric pair vs pT1, pT2. How to translate this into single yield from jet?

2 2coll AA

coll AA

N JJet Pairs

Combinatoric Pairs N R

Jet contribution at low pT?

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Ridge and cone : different mechanism?

Both have similar property in pT and PID composition and softer than jet. They are results of same matter, ridge and cone mechanism should play a role on bot

h sides. Reduced/no surface bias for intermediate pT correlation.

Ridge

Cone

Near jet

Away jet

0

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Summary

Jet correlation @ high pT provide constraints on the <eloss> and geometrical bias

Jet correlation @ intermediate pT shows complex evolution due to competition between Jet quenching and medium response on both near- and away-side.

Constrain the particle production mechanism by combing single and correlation landscape in pT.

Physics varying drastically with pT, good model should describe the full pT dependence.

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Backup

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Head region: jet punch-through Low pTB range, decrease with Npart

Turn on of jet quenching, soft contribution dominates High pTB range, flat with Npart

Punch through jet dominate and has same slope (soft contribution dies out)

STAR Preliminary

||<0.4

dn/d

Fuqiang

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Details of the suppression and enhancement

AAAA

pp

PerTriggerYieldI

PerTriggerYield

HR exhibits early onset of suppression, relative to p+p, approach Raa at high pT: jet quenching!

H+S (entire away side) exhibits overall enhancement due to SR, up to pT

A,B <4 GeV/c

IAA depends on the integration window!

arXiv:0705.3238 [nucl-ex]

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Integration range and pT matters! One might reach misleading conclusion if only focus on limited pT.

No Modification seen in HR for this pTA x pTB bin but: Would see enhancement for this pTA x pTB bin in the SR+HR, and At high pT, would see a suppression even in SR+HR, and At low pT, would see an enhancement even in HR.

Thus it is important to map out the full pTA, pTB and space!

HRSR

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pT evolution of jet function

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