1. In-Medium Properties of Jets
from
Fuqiang Wang
tool  goal.

2. Quark Matter 2006, Shanghai, China – Fuqiang Wang
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, Dh long range correlation.
charged hadrons (large statistics):
will not cover identified hadron, or g-h, or e-h correlations.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

3. punch-through at high pT
STAR, PRL 97 (2006)
8 < pT(trig) < 15 GeV/c
clear away-side peak – dijets
little modification on near side
suppression of away-side yield
but little modification to away-side shape
J. Jia (PHENIX), nucl-ex/
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

4. no change in away-side shape
data look clean and simple, the underlying physics may not!
away-side widths similar for central and peripheral, also for different pT.
8 < pT(trig) < 15 GeV/c
6<pT(trig)<8 GeV/c
Au+Au 40-80%
Magestro (STAR), QM 2005. 1 1 2 2 3 3
finite prob. of not interacting: fragmentation as in vacuum?
fragment in medium, then hadrons lose energy with insignificant broadening at large pT?
lose some energy, and then fragment?
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

5. “disappearance” at intermediate pT
Cu+Cu less suppressed, consistent with pathlength difference.
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 less suppressed, consistent with pathlength difference.
Cu+Cu top 10%
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

6. reaction plane dependence
J. Jia (PHENIX), nucl-ex/
STAR, PRL93 (2004)
Difference hangs on only 1 data point.
|ftrig-fRP|
Hint of stronger suppression out-of-plane than in-plane, consistent with energy loss picture.
Hint of stronger double-peak structure out-of-plane than in-plane.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

7. enhanced, broadened, softened at low pT
STAR, PRL95 (2005)
F.Wang (STAR), QM’05, nucl-ex/
<pT> from away jets
<pT> from medium decay
hard
soft
similar
Away side <pT> (GeV/c)
pTtrig=4-6 GeV/c
pTassoc= GeV/c
Enhanced correlated yields.
Broadened and softened away-side.
hard-soft: approach thermalization.
soft-soft (larger x-section): higher degree of thermalization.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

8. double-humped for some pT ranges
trigger pT =2.5-4 GeV/c, associated pT = GeV/c
STAR Preliminary
5-10%
10-20%
20-40%
40-60%
60-80%
J.G. Ulery (STAR), QM’05, nucl-ex/ ; M. Horner, parallel 3.2, Nov.19.
0-5%
PHENIX, PRL97 (2006)
PHENIX, nucl-ex/
away
hump
dashed=PHENIX, solid=STAR*0.35
Away-side center does not drop (stays roughly constant).
The hump increases with centrality: shock wave excitation?
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

9. <pT> is dipped at p !
J. Jia (PHENIX), nucl-ex/
2.5<pT(trig)<4 GeV/c
F.Wang (STAR), QM’05, nucl-ex/
<pT> (GeV/c)
Away side
Hadrons in the double-hump are harder: shock wave push?
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

10. Quark Matter 2006, Shanghai, China – Fuqiang Wang
shock wave push?
Scheid, Muller, Greiner, Phys. Rev. Lett. 32, 741 (1974); Hofmann, Stoecker, Heinz, Scheid, Greiner, PRL 36, 88 (1976).
Many recent studies: Stoecker, nucl-th/ ; Casalderrey-Solana, Shuryak, Teaney,
hep-ph/ ; Ruppert, Muller, hep-ph/ ; Chaudhuri, Heinz, nucl-th/ ; Renk, Ruppert, PRC73 (06) , Y.G. Ma, et al., nucl-th/ …
near-side
trigger
away-side jet axis Df
projection
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.
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/ ; …or deflected jets.
Medium
away
near
deflected jets
high pT parton
Rudy Hwa
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.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

11. discrimination by 3-particle correlation
Need 3-particle correlation to discriminate different physics mechanisms. π
Δ1
Δ2 π
Δ1
Δ2
Medium
away
near
di-jets
Medium
away
near
deflected jets
Δ1
Trigger
Δ2
away
near
Medium
mach cone
Δ1
Δ2 π
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

12. 3-particle correlation backgrounds
Jason Ulery (STAR), HP’06, nucl-ex/ ; J.G. Ulery, FW, nucl-ex/
Claude Pruneau, STAR talk, Parallel 1.3, Nov.15; Jason Ulery, STAR poster # 44.
bkgd
jet
Δ1
Trigger
Δ2
1/Ntrig d2N/dDf1dDf2
Δ2
raw = (jet+bkgd) x (jet+bkgd)
jet x jet = raw –
(bkgd x bkgd) –
(jet x bkgd)
pTtrig=3-4 GeV/c
pTassoc=1-2 GeV/c
Δ1
bkgd x bkgd
jet x bkgd - +
trigger
flow
trigger
flow
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

13. 3-particle correlation signalpp
d+Au
Au+Au 50-80%
Au+Au 30-50%
Au+Au 10-30%
Au+Au 0-10%
3-particle correlation signal
J.G. Ulery (STAR), HP’06, nucl-ex/ ;
Claude Pruneau, STAR talk, Parallel 1.3;
Jason Ulery, STAR poster # 44.
pTtrig=3-4 GeV/c, pTassoc=1-2 GeV/c
Au+Au central 0-12% ZDC
Δ2
Δ1
1/Ntrig d2N/dDf1dDf2
Elongation along away diagonal: kT broadening, deflected jets.
Evidence of conical emission in central Au+Au collisions.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

14. ZDC central 12% Au+Au Conical emission signal in central Au+Au.
=(1+2)/2
=(1-2)/2
1/Ntrig dNtriplet/dDf
projection along
off-diagonal diagonal
Au+Au central 0-12% ZDC
Δ2
Δ1
1/Ntrig d2N/dDf1dDf2
=(1+2)/2-p
1/Ntrig dNtriplet/dDf
=(1-2)/2
Major sources of systematic errors: flow, background normalization.
Conical emission signal in central Au+Au.
Other contributions (such as deflected jets) present.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

15. cone angle Cone angle consistent with no pT dependenc 
Jason Ulery, STAR poster # 44.
Au+Au 0-12% ZDC
Δ2
Δ1
cone angle (radians)
(Npart/2)1/3
pTassoc (GeV/c)
Au+Au ZDC 12%
Au+Au 0-50%
1/Ntrig d2N/dDf1dDf2
Cone angle consistent with no pT dependenc 
Conical emission consistent with Mach-cone shock waves, not simple Cerenkov gluon radiation.
Cone angle: q ~ 1.45 ~ 80o
cos(q) ~ =??? cS
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

16. 3-particle signal strength
Au+Au 0-12% ZDC
Δ1
Δ2
J.G. Ulery (STAR), HP’06, nucl-ex/ ; STAR poster # 44.
1/Ntrig d2N/dDf1dDf2
Away
Cone
Deflected
+ Cone
signal / radian2
(Npart/2)1/3
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

17. polar coord. analysis Background from mixed-events.
N.N. Ajitanand (PHENIX), poster # 39.
Same Side
Away Side
Background from mixed-events.
Background subtracted.
3-particle correlation in PHENIX acceptance, consistent with MC.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

18. Quark Matter 2006, Shanghai, China – Fuqiang Wang
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 p.
Three-particle jet-correlation: Evidence for conical emission. Cone angle ~ 1.45.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

19. Quark Matter 2006, Shanghai, China – Fuqiang Wang
backups
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

20. Enhancement at low pt
STAR, PRL95 (2005)
Enhanced and broadened away-side distribution at low pT.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

21. 3-particle signal strength
J.G. Ulery (STAR), Hard Probes 06, nucl-ex/ ; QM’06 poster # 44.
Au+Au 0-12% ZDC
Δ1
Δ2
1/Ntrig d2N/dDf1dDf2
ZDC
Major sources of systematic errors: flow, background normalization.
Mach cone signal in central Au+Au collisions.
Contribution from deflected jets present.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

22. Quark Matter 2006, Shanghai, China – Fuqiang Wang
Flow systematics
reaction plane v2
Flow is varied between the modified reaction plane result and the 4- particle cumulant result.
Result is robust with the variation in v2. _
4-particle cumulant v2
Jason Ulery (STAR), Hard Probes 2006.
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

23. Background normalization systematic
default
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.
Jason Ulery (STAR), Hard Probes 2006.
wide norm. region
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

24. Quark Matter 2006, Shanghai, China – Fuqiang Wang
Au+Au 0-12%
(1+2)/2
(1-2)/2
Δ2
Δ1
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
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

25. cumulant vs jet-like with no flow
J.G. Ulery, FW, nucl-ex/
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang

26. cumulant vs jet-like with flow
J.G. Ulery, FW, nucl-ex/
16 November 2006
Quark Matter 2006, Shanghai, China – Fuqiang Wang