In-Medium Properties of Jets

Medium Properties

Fuqiang Wang

In-Medium Jets

from

In-Medium Properties of Jets

16 November 2006 Quark Matter 2006, Shanghai, China – Fuqiang Wang 2

Outline

• “punch-through” at high pT

• “disappearance” at intermediate pT

• enhancement at low pT

• medium collective response

mid-rapidity (the most interesting region): will not cover forward-rapidity jet-correlation.

away-side (strongest modification): will not cover near-side correlation, long range correlation.

charged hadrons (large statistics): will not cover identified hadron, or -h, or e-h correlations.


punch-through at high pT

• clear away-side peak – dijets

• little modification on near side

• suppression of away-side yield

• but little modification to away-side shape

8 < pT(trig) < 15 GeV/cSTAR, PRL 97 (2006) 162301.

J. Jia (PHENIX), nucl-ex/0510019.


6<pT(trig)<8 GeV/c

Au+Au 40-80%

Magestro (STAR), QM 2005.

8 < pT(trig) < 15 GeV/c

no change in away-side shape

away-side widths similar for central and peripheral, also for different pT.

1

2

3

2

3

1. finite prob. of not interacting: fragmentation as in vacuum?

2. fragment in medium, then hadrons lose energy with insignificant broadening at large pT?

3. lose some energy, and then fragment?

1


“disappearance” at intermediate pT

• near-side unchanged• away-side nearly disappeared -

consistent with “surface emission”• d+Au ~ p+p: final state effect• qualitatively intuitive for jet-

suppression, but quantitatively not simple.

away-side yield seen

above background

Cu+Cu top 10%

Cu+Cu less suppressed, consistent with pathlength

difference.


reaction plane dependence

Hint of stronger suppression out-of-plane than in-plane, consistent with energy loss picture.

STAR, PRL93 (2004) 252301.

|trig-RP|Hint of stronger double-peak structure out-of-plane than in-plane.



enhanced, broadened, softened at low pT

<pT> from away jets

<pT> from medium decay

hard

soft similar

Aw

ay s

ide <

pT>

(G

eV

/c)

pTtrig=4-6 GeV/c

pTassoc=0.15-4 GeV/c

hard-soft: approach thermalization.

soft-soft (larger x-section): higher degree of thermalization.

STAR, PRL95 (2005) 152301.F.Wang (STAR), QM’05, nucl-ex/0510068.

• Enhanced correlated yields.• Broadened and softened away-side.


double-humped for some pT rangestrigger pT =2.5-4 GeV/c, associated pT =1.0-2.5 GeV/c

PHENIX, PRL97 (2006) 052301.

STAR Preliminary

5-10%

10-20% 20-40%

40-60% 60-80%

J.G. Ulery (STAR), QM’05, nucl-ex/0510055;M. Horner, parallel 3.2, Nov.19.

0-5%

awayhump

dashed=PHENIX, solid=STAR*0.35

PHENIX, nucl-ex/0611019.

• Away-side center does not drop (stays roughly constant).

• The hump increases with centrality: shock wave excitation?


<pT> is dipped at !

Hadrons in the double-hump are harder: shock wave push?


2.5<pT(trig)<4 GeV/c

Aw

ay s

ide

<p

T>

(G

eV

/c)

F.Wang (STAR), QM’05, nucl-ex/0510068.


shock wave push?

near-sidetrigger

away-side jet axis

projection

Mediumaway

near

deflected jets

deflected jets: well confined in each event but deflected at varying angle.

preferential selection of jet particles: those directed inwards are harder to get out because of energy loss.high pT

parton

Rudy Hwa

Double-peak structure can also be generated by large angle gluon radiation: Vitev, Phys. Lett. B630 (2005) 78; A.D. Polosa and C.A. Salgado, hep-ph/0607295; …or deflected jets.

Perfect fluid of hot and dense matter at RHIC: cS, supersonic jets, jet-quenching.RHIC appears to have all the conditions to generate Mach-cone shock waves.

Scheid, Muller, Greiner, Phys. Rev. Lett. 32, 741 (1974); Hofmann, Stoecker, Heinz, Scheid, Greiner, PRL 36, 88 (1976).Many recent studies: Stoecker, nucl-th/0406018; Casalderrey-Solana, Shuryak, Teaney,

hep-ph/0411315; Ruppert, Muller, hep-ph/0503158; Chaudhuri, Heinz, nucl-th/0503028; Renk, Ruppert, PRC73 (06) 011901, Y.G. Ma, et al., nucl-th/0601012. …


Δ1

Trigger

Δ2

discrimination by 3-particle correlation

Mediumaway

near

deflected jets

away

near

Medium

mach cone

Medium

away

near

di-jets

Need 3-particle correlation to discriminate different physics mechanisms.

0

0

π

π

Δ1

Δ2

Δ1

Δ2

0

π

0 π

0

π

0 π Δ1

Δ2


3-particle correlation backgrounds

Δ1

Δ

pTtrig=3-4 GeV/c

pTassoc=1-2 GeV/c

-+ triggerflow

triggerflow

bkgd

jet

bkgd x bkgd jet x bkgd

1/N

trig d2N

/d

1 d

2

Δ1

Trigger

Δ2

Jason Ulery (STAR), HP’06, nucl-ex/0609047; J.G. Ulery, FW, nucl-ex/0609017.Claude Pruneau, STAR talk, Parallel 1.3, Nov.15; Jason Ulery, STAR poster # 44.

raw = (jet+bkgd) x (jet+bkgd)

jet x jet = raw –(bkgd x bkgd) – (jet x bkgd)


3-particle correlation signal

pp d+Au

Au+Au 50-80% Au+Au 30-50%

Au+Au 10-30% Au+Au 0-10%

J.G. Ulery (STAR), HP’06, nucl-ex/0609047;Claude Pruneau, STAR talk, Parallel 1.3;

Jason Ulery, STAR poster # 44.

• Elongation along away diagonal: kT broadening, deflected jets.

• Evidence of conical emission in central Au+Au collisions.

pTtrig=3-4 GeV/c, pT

assoc=1-2 GeV/cAu+Au central 0-12% ZDC

Δ2

Δ1

1/N

trig d2N

/d

1 d

2


ZDC central 12% Au+AuAu+Au central 0-12% ZDC

Δ2

Δ1

1/N

trig d2N

/d

1 d

2

=(1+2)/2=(12)/21/N

trig d

Ntr

iple

t/d

projection alongoff-diagonal diagonal

=(1+2)/2

1/N

trig d

Ntr

iple

t/d

=(12)/2

• Major sources of systematic errors: flow, background normalization.

• Conical emission signal in central Au+Au.

• Other contributions (such as deflected jets) present.


cone angle

Cone angle consistent with no pT dependenc Conical emission consistent with Mach-cone shock waves, not simple Cerenkov gluon radiation.Cone angle: ~ 1.45 ~ 80o

cos() ~ 0.12 =??? cS

Au+Au 0-12% ZDC

Δ2

Δ1

Jason Ulery, STAR poster # 44.

1/N

trig d2N

/d

1 d

2 cone a

ngle

(ra

dia

ns)

(Npart/2)1/3

pTassoc (GeV/c)

cone a

ngle

(ra

dia

ns) Au+Au ZDC 12%

Au+Au 0-50%


(Npart/2)1/3

Au+Au 0-12% ZDC

Δ1

Δ2

3-particle signal strength

1/N

trig d2N

/d

1 d

2

Away Cone Deflected+ Cone

J.G. Ulery (STAR), HP’06, nucl-ex/0609047; STAR poster # 44.

sig

nal /

rad

ian

2


polar coord. analysis

Same Side

Away Side

*

*

N.N. Ajitanand (PHENIX), poster # 39.

• Background from mixed-events.• Background subtracted.• 3-particle correlation in PHENIX

acceptance, consistent with MC.


Conclusions

• Di-jets present in heavy ions at sufficiently high pT. Angular distribution little modified, correlated yield per trigger strongly suppressed.

• At intermediate pT, di-jets strongly suppressed that no appreciable di-jets survive.

• Rich phenomena at low pT: enhanced, broadened (even double-humped), and softened. The <pT> is the lowest at .

• Three-particle jet-correlation: Evidence for conical emission. Cone angle ~ 1.45.


backups


Enhancement at low pt

STAR, PRL95 (2005) 152301.

Enhanced and broadened away-side distribution at low pT.


3-particle signal strength

• Major sources of systematic errors: flow, background normalization.

• Mach cone signal in central Au+Au collisions.

• Contribution from deflected jets present.

Au+Au 0-12% ZDC

Δ1

Δ2

J.G. Ulery (STAR), Hard Probes 06, nucl-ex/0609047; QM’06 poster # 44.

ZDC

1/N

trig d2N

/d

1 d

2


Flow systematics

• Flow is varied between the modified reaction plane result and the 4- particle cumulant result.

• Result is robust with the variation in v2.

reaction plane v2

4-particle cumulant v2

_ _

Jason Ulery (STAR), Hard Probes 2006.


Background normalization systematic

• Normalization within |Δ±1|<0.175 assuming zero yield at minimum.

• Default uses a normalization range of 0.35.

• Normalization range of 0.70 used to check systematic.

• Result is robust with respect to normalization range.

default

wide norm. region

Jason Ulery (STAR), Hard Probes 2006.


Au+Au 0-12%

(1+2)/2

(1-2)/2

Δ2

Δ1

v2(jet) = v2(trig) v2(jet) = 0

(1+2)/2

(1-2)/2

Filled: v2(jet) = v2(trig)Open: v2(jet) = 0

(1-2)/2

(1+2)/2


cumulant vs jet-like with

no flow

3 1 2 3 1 2

2 2 1 2 2 2

ˆˆ ( , ) ( , )

ˆ ˆ ˆ ˆ( ) ( )

J

J J J J

3 1 2 2 1 2 2

3 1 2 2 1 2 2 2 2

If

ˆ ˆ ˆ( , ) ( ) ( )

then

ˆ ˆ ˆ ˆˆ ( , ) ( ) ( )

J J J

J J J J

J.G. Ulery, FW, nucl-ex/0609017.


cumulant vs jet-like with

flow

J.G. Ulery, FW, nucl-ex/0609017.

3 1 2 3 1 2

2 2 1 2 2 2

(2) (2)1 2 1 2 2 2 2 4 4 2

(1) (1)1 2 2 2 2 2 1 4 4 1

(1) (2)2 1 2 2 2

ˆˆ ( , ) ( , )

ˆ ˆ ˆ ˆ( ) ( )

ˆ ˆ( ) 2 cos 2( ) 2 cos 4( )

ˆ ˆ( ) 2 cos 2( ) 2 cos 4( )

ˆ ˆ2 2 c

trig trig

trig trig

J

J J J J

B J J v v v v

B J J v v v v

J B J v v

(1) (2)1 2 4 4 1 2

2 (1) (2) (2) (1) (1) (2)1 2 2 4 1 2 2 2 4 1 2 2 2 4 1 2

os 2( ) 2 cos 4( )

2 cos 2( 2 ) 2 cos 2(2 ) 2 cos 2( ) .trig trig trig

v v

B v v v v v v v v v

In-Medium Properties of Jets

Documents

jet bkgd x jet bkgdjet

rapidity jetcorrelation

pt rangestrigger pt

different pt

shock wave push

deflected jets

associated pt

shock wave excitation