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1
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?
2
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
3
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
4
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?
5
53
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
6
53
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
7
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
8
High pT : Geometrical bias
IAA RAA, Why??STAR, Phys. Rev. Lett. 97 (2006) 162301
I AA
Transmission, Absorption shift
T. Renk notation
0.2
9
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
10
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
11
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
12
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]
13
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
15
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
17
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
18
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
19
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?
20
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
21
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
22
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
23
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
24
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
25
Near side Iaa
We calculate the pair suppression factor, Jaa, from Iaa and Raa
RAA
26
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
=
27
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
28
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.
53
RAA
pT
1
Jet
Flow+coalescense
0.2
29
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?
30
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
31
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.
32
Backup
33
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
34
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]
35
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
36
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pT evolution of jet function
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