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Jet%20Correlations

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Title: Jet%20Correlations


1
Jet Correlations
  • Mike Miller (Yale University)

2
Why Jets?
  • Hard probe?early time
  • Calculable pQCD
  • Abundant at RHIC, LHC

3
Moment Analysis of QCD Matter
4
Partonic vs. Hadronic Mechanisms
  • Hottest Questions
  • Fragment inside/outside of medium?
  • Partonic vs. hadronic model of Final State
    interaction?
  • A Better Question
  • To what degree do partonic and hadronic
    interactions contribute to quenching?
  • Discussion only recently started!

5
4 Ways to Skin a Cat Jet
1) Integral Distributions ltpTgt, ltNchgt
2) Single Particle Spectra d?/dpT ? RAA, RdA
3) 2-Particle Correlations dN/d(??)
4) Jet Reconstruction d?/dET, Frag. Func.
6
Disappearance of the away-side
Disappearance (at mid-rapidity) is dominated by
final state effect(s)! Jet Quenching
2nd order correlations due to elliptic flow of
entire event ?competing background
Adler et al., PRL90082302 (2003), STAR
  • pp
  • 2-jets

1/NtriggerdN/d(??)
  • Peripheral AuAu
  • 2-jets

di-hadron
  • Central AuAu
  • 1-jet!

Background subtracted
7
Questions Raised at QM02
  • Initial state effects?
  • What should 2-particle correlation look like?
  • Partonic/nuclear kT
  • jT
  • Measurable at SPS?
  • Final state energy loss?
  • Baryons vs. Mesons?
  • PID?
  • Background subtraction?
  • Jets correlated with reaction plane?
  • And many more

8
Path Length Dependence
Background Subtracted See J. Bielcikova et al.,
(nucl-ex/0311007) for background derivation
di-hadron, 20-60 Central
STAR Preliminary
Out-of-plane
In-plane
K. Filimonov DNP03
9
Path Length Dependence
Background Subtracted See J. Bielcikova et al.,
(nucl-ex/0311007) for background derivation
di-hadron, 20-40 Central
Out-of-plane
In-plane
Quenching Consistent with path length Dependence
10
Jet Fragmentation Shape
parton
parton
11
kT, jT at RHIC from pp Data
Statistical Errors Only
di-hadron
J. Rak, Wed.
J. Rak, DNP03
PHENIX preliminary
Df
near-side
away-side
12
kT, jT at RHIC from pp Data
Statistical Errors Only
PHENIX preliminary ?jTy? 359?11
MeV/c ?kTy? 964?49 MeV/c
di-hadron
Good agreement with previous measurements
PLB97 (1980)163 PRD 59 (1999) 074007
J. Rak, DNP03
PHENIX preliminary
kT, jT from pp, dAu, AuAu from ?0-hadron,
di-hadron, jet, di-jet ?Friday Completing the
reference measurements!
13
AuAu near-side Jet-like at all centralities?
Yes, but widens in ?? (see c07)
14
Quenching at SPS?
charged-pion pairs
mid-central
central
pTgt1.2 GeV/c
Accepted by PRL, nucl-ex/0303014, CERES
15
Quenching at SPS?
16
Di-Hadrons at all pT
See F. Wang, Fri. QM04
di-hadron correlations
  • mixed event background subtraction
  • elliptic flow background subtraction
  • ?Study fragmentation in pp, AuAu
  • Full range in pT
  • Transport from high-pT to low-pT?
  • Change in jet size?

Study pT distribution in near- and away-side jet
cones
17
Di-Hadrons at all pT
di-hadron correlations
Near-Side
Away-Side
F. Wang, DNP03
STAR Preliminary
See F. Wang Friday
18
pT Distribution in Near-Side Jet
di-hadron correlations
Near-Side
F. Wang, DNP03
STAR Preliminary
ratio
AuAu/pp
See F. Wang Friday
19
pT Distribution in Away-Side Jet
di-hadron correlations
Near-Side
Away-Side
F. Wang, DNP03
STAR Preliminary
ratio
ratio
AuAu/pp
See F. Wang Friday
20
Is The Away-Side Jet-Like?
STAR Preliminary
pp
AuAu 0-5
(1/Ntrig) dN/d(Df)
Background subtracted
Background subtracted
Df
Df
Away-side looks jet-like in pp, not central
AuAu!
So whats going on?
See F. Wang Friday
21
Is The Away-Side Jet-Like?
STAR Preliminary
Fit to near side const. gaussian
Borghini-cos(fixed)
pp
AuAu 0-5
(1/Ntrig) dN/d(Df)
Background subtracted
Background subtracted
Df
Df
Amplitude -Depends on pT window -Can be
tested -Work in progress (see )
See F. Wang Friday
22
What could this mean?
STAR Preliminary
Fit to near side const. gaussian
Borghini-cos(fixed)
pp
AuAu 0-5
(1/Ntrig) dN/d(Df)
Background subtracted
Background subtracted
Df
Df
Optimist Maybe the most exciting result yet!
Pessimist A fundamentally boring resultAnother
background
See F. Wang Friday
23
Conclusions
  • 2-particle correlations
  • Successful measure of hard-scattering,
    fragmentation
  • Away-side quenching in central AuAu
  • Indicative of strong final state interactions
  • In/out-of plane consistent with path length
    dependence
  • Semi-hard scattering at SPS
  • Present at all centralities
  • Large away-side broadening
  • Near-side correlations in AuAu
  • Consistent with fragmentation at all centralities
  • pT distribution in near- and away-side jet cones
  • Consistent with modified fragmentation?

24
The Real Conclusions
  • 2-particle correlations
  • Robust jet probe from pp to central AuAu
  • QM02?Disappearance of away-side jet
  • QM04?Finding the lost-energy on the away-side
  • Qualitative consistency between PHENIX and STAR
  • Transport from high pT ? low pT
  • But away-side has lost jet-like shape!

25
Future Directions at RHIC
  • Minimize ambiguities, sensitivities
  • Higher trigger pT ? only jet production
  • higher trigger pT ? smaller kT effects
  • Higher statistics test of path length dependence
  • Away-side pT transport
  • dAu?
  • Trigger-pT dependence?
  • Punch through above momentum conservation?
  • Calibrate the jet-energy scale photon-jet
  • Mass effect heavy quarks vs. light quarks ?E
  • Color charge quark vs. gluon jets?

26
Old
27
Back side correlations between charged hadrons
3.7 GeV lt PT trigger lt4.5 GeV
5.4 GeV lt PT trigger lt6.5 GeV
2.5 GeV lt PT associated lt3.7 GeV
2.5 GeV lt PT associated lt3.7 GeV
Trigger PT
Fig. 12 Same side and back side as function of
Trigger PT
1/NtriggerdN/d(?F)
1/NtriggerdN/d(?F)
same side is calculated by integrating the
Gaussian component and the back side is
calculated by integrated the cosine component.
Notices that there is a back side signal for the
higher PT correlation
?F (radians)
?F (radians)
4.5 GeV lt PT trigger lt5.4 GeV
6.5 GeV lt PT trigger lt10 GeV
2.5 GeV lt PT associated lt3.7 GeV
2.5 GeV lt PT associated lt3.7 GeV
1/NtriggerdN/d(?F)
1/NtriggerdN/d(?F)
Trigger PT
Fig. 13
?F (radians)
?F (radians)
In Fig.13. The fitting Ccos is compared to
estimation due to the momentum conservation6.
Fig. 11 Charged Hadrons correlations for
different trigger PT range
Fitting Function
28
Path Length Dependence
Background Subtracted See J. Bielcikova et al.,
(nucl-ex/0311007) for background derivation
di-hadron, 20-60 Central
STAR Preliminary
K. Filimonov DNP03
Quenching Consistent with path length Dependence!
29
Path Length Dependence
Background Subtracted See J. Bielcikova et al.,
(nucl-ex/0311007) for background derivation
di-hadron, 20-60 Central
STAR Preliminary
In-plane
K. Filimonov DNP03
Quenching Consistent with path length Dependence!
30
Away-Side Quenching (2002)
2nd order correlations due to elliptic flow of
entire event ?competing background
Adler et al., PRL90082302 (2003), STAR
1/NtriggerdN/d(??)
di-hadron
  • Central AuAu
  • 1-jet!

Background subtracted
31
Away-Side Quenching (2002)
2nd order correlations due to elliptic flow of
entire event ?competing background
Adler et al., PRL90082302 (2003), STAR
1/NtriggerdN/d(??)
di-hadron
  • Central AuAu
  • 1-jet!

Background subtracted
32
Conclusions
  • 2-particle correlations
  • Successful measure of hard-scattering,
    fragmentation
  • Jet-like correlations at all centralities in
    AuAu
  • Away-side correlations
  • pT distribution in near- and away-side jet cones
  • Consistent with modified fragmentation?

33
Unraveling final state mechanisms at RHIC
  • Minimize ambiguities, sensitivities
  • Higher trigger pT ? only jet production
  • higher trigger pT ? smaller kT effects
  • Higher statistics test of path length dependence
  • Away-side pT transport
  • dAu?
  • Trigger-pT dependence?
  • Punch through above momentum conservation?
  • Calibrate the jet-energy scale photon-jet
  • Mass effect heavy quarks vs. light quarks ?E
  • Color charge quark vs. gluon jets?
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