understanding jet energy loss with angular correlation studies in phenix
DESCRIPTION
Understanding Jet Energy Loss with Angular Correlation Studies in PHENIX. Ali Hanks for the PHENIX Collaboration 24 th Winter Workshop on Nuclear Dynamics South Padre Island, TX April 8th, 2008. Outline. Motivation and some background. Away-side "Mach-cone" effect. - PowerPoint PPT PresentationTRANSCRIPT
Understanding Jet Energy Loss Understanding Jet Energy Loss with Angular Correlation Studies with Angular Correlation Studies
in PHENIXin PHENIX
Ali Hanksfor the PHENIX Collaboration
24th Winter Workshop on Nuclear Dynamics South Padre Island, TX April 8th, 2008
April 8, 2008Ali Hanks - WWND
OutlineOutline
• Motivation and some background
• Away-side "Mach-cone" effect
• Near-side "ridge"
• Correlations with photons
• Conclusions
April 8, 2008Ali Hanks - WWND
Jet fragmentation in Au+AuJet fragmentation in Au+Au
• Near-side
– jet + ridge (medium response?)
• Away-side– Head region (suppressed - jet modification)
– Shoulder region (medium response)
p+p Au+Au
April 8, 2008Ali Hanks - WWND
ppTT evolution of correlations evolution of correlationsIn
crea
se tr
igge
r p T
Yield enhanced
Shoulder structure remains
Jet reemerges
April 8, 2008Ali Hanks - WWND
ppTT evolution of correlations evolution of correlationsIncrease partner pT
Yield suppressed
Jet reemerges
Yield enhanced
April 8, 2008Ali Hanks - WWND
Away-side modificationAway-side modification
• Modified jet yield vs pT
– enhancement at low pT
– suppression at high pT
• Agrees well with expected jet energy loss and induced gluon radiation
• Shoulder is ehanced up to pT~ 4GeV/c
I AA
April 8, 2008Ali Hanks - WWND
Away-side head vs shoulderAway-side head vs shoulder
• Shoulder enhanced up to pT ≈ 4GeV/c
April 8, 2008Ali Hanks - WWND
Away-side peak positionsAway-side peak positions
• Fit Method 1:
– 2 guassian away-side seperated by D
• Fit Method 2:
– 3 guassian away-side
• one fixed by p+p centered at
• 2 seperated by D
Weak pTdependence best explained by mach-cone models
April 8, 2008Ali Hanks - WWND
Away-side compositionAway-side composition
• Shape similar for mesons and baryons– provides constraint on
models describing modification of away-side
• Baryon to Meson ratio similar to the bulk– incosistent with vacuum
fragmentation
– consistent with jet induced medium excitation
April 8, 2008Ali Hanks - WWND
Near-side Near-side • Broadening in
up to pT ≈ 4GeV/c
• Subtracting p+p distribution leaves flat background
– consistent with ~flat ridge + unmodified jet
April 8, 2008Ali Hanks - WWND
The ridge and shoulder connectionThe ridge and shoulder connection• ridge and shoulder pT spectra are
softer in Au+Au than in p+p– Shoulder is close to inclusive
– ridge may be harder than shoulder
• ridge and shoulder balance
April 8, 2008Ali Hanks - WWND
Going to high pGoing to high pTT
• Suppression at high pT agrees with
jet energy loss expectations
• Widths unmodified within errorsI AA
• But broadening is predicted
April 8, 2008Ali Hanks - WWND
Geometric Bias?Geometric Bias?
• -jet– photon non-interacting so no bias effect on trigger
– possible associated hadron surface bias at high pT
• 2+1 correlations: additional condition of high pT particle on
away-side– reduce surface bias
– still susceptible to tangential bias
trigger
additional away-side particle
partner
tangential bias
surface biasMach coneridge
intermediate pT high pT
Solutions (?):
April 8, 2008Ali Hanks - WWND
1/N
trig
dN
/d
(A
.U.)
Run 6 p+p @ 200 GeV
-jet correlations in p+p-jet correlations in p+p• Photon momentum balances with away-side jet
– sensitive to the FF
• Statistical subtraction
– Technique works over large pT range in p+p
– Rγ = N(inclusive γ)/N(decay γ)
Run 6 p+p @ 200 GeV
Per
-Tri
gger
Yie
ld (
A.U
.)
pT trigger
Leading order (LO)
compton annihilation
April 8, 2008Ali Hanks - WWND
-jet correlations in Au+Au-jet correlations in Au+Au
Run7 Au+Au 200 GeV12-15 X 3-5 GeV
CF
(A
.U.)
Run7 Au+Au 200 GeV7-9 X 3-5 GeV
CF
(A
.U.)
• Suggests away-side suppresion in Au+Au– sensitive to energy loss of jet
inclusive -h
April 8, 2008Ali Hanks - WWND
Fragmentation photonsFragmentation photons
• Medium induced modifications highly sensitive to energy loss of jets
• Direct measurement will improve experimental sensitivity
• p+p measurement important test of pQCD
– LHC--RHIC
Next to leading order (NLO)
Medium induced modifications:
April 8, 2008Ali Hanks - WWND
Fragmentation photonsFragmentation photons• First measurement of it's kind at
RHIC– next step measure jet shape properties
– ultimately apply procedure to Au+Au
Nfrag/Ninc ≈ 0.1 at intermediate pT
April 8, 2008Ali Hanks - WWND
ConclusionsConclusions
Modification to two particle correlations seen in Au+Au collisions on both the near and away-side
– away-side pT dependence consistent with mach cone scenario
while challenging gluon radiation and deflected jet models
– modification at intermediate pT suggests dominance of jet
induced medium excitations
– high pT dominated by jet fragmentation
• away-side suppresion consistent with energy loss
• unmodified near-side and no observation of broadening in away-side suggests geometric bias
– -jet and h- correlations can provide new insight
April 8, 2008Ali Hanks - WWND
Backup SlidesBackup Slides
April 8, 2008Ali Hanks - WWND
2+1 correlations2+1 correlations
April 8, 2008Ali Hanks - WWND
Near-side modificationNear-side modification
• Enhancement at low pT
• "Suppression" at high associated pT
and low trigger pT
– dillusion effect?
I AA
• Broadening in Df at low trigger and associated pT
• Agrees with p+p at high pT
April 8, 2008Ali Hanks - WWND
Near side compositionNear side composition
April 8, 2008Ali Hanks - WWND
Going to higher pGoing to higher pTT - the near-side - the near-sideI A
A
April 8, 2008Ali Hanks - WWND
Ridge cont'dRidge cont'd
April 8, 2008Ali Hanks - WWND
Ridge vs Shoulder cont'dRidge vs Shoulder cont'd
0712.3033 nucl-ex
Near-side Away-side
April 8, 2008Ali Hanks - WWND
Predictions from theoryPredictions from theory