Hot Quarks 2004, Taos Ski Valley, New Mexico

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Hot Quarks 2004, Taos Ski Valley, New Mexico
Di-Hadron Correlations at High pt
Kirill Filimonov
Lawrence Berkeley National Laboratory

• Di-hadron correlations in pp,dAu,AuAu at 200 GeV
• What should we expect in AuAu at 62 GeV?

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How it all started
Reconstructing jets in AuAu on a statistical
basis
STAR, PRL 90082302,2003 AuAu _at_ 200 GeV/c 0-5
most central 4 lt pT(trig) lt 6 GeV/c 2 lt
pT(assoc.) lt pT(trig)
STAR, PRL 9003201,2003 AuAu _at_ 130 GeV/c 0-10
most central 4 lt pT(trig) lt 6 GeV/c 2 lt
pT(assoc.) lt pT(trig)
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Suppression of back-to-back jets
Peripheral Au Au

• Near-side well-described
• Away-side suppression in central collisions

STAR, PRL 90082302,2003
STAR
near side
Central Au Au
away side
Away side jets are suppressed!
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Back-to-back jet suppression is a final state
effect
STAR, Phys.Rev.Lett.91072304,2003
Back-to-back jets are strongly suppressed in
central AuAu collisions but not in dAu
collisions
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Di-hadron correlations wrt reaction plane
STAR, nucl-ex/0404007 pTtrigger4-6
GeV/c, 2ltpTassociatedltpTtrigger, ?lt1
Flow pattern is shifted by ?/2 J. Bielcikova,
S.Esumi, KF, S.Voloshin, and J.P.Wurm Phys.Rev.C69
021901,2004
Back-to-back suppression depends on the reaction
plane orientation energy loss dependence on the
path length
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Theoretical challenges
F.Wang, STAR Preliminary 4 lt pt(trig) lt 6 GeV/c
STAR, PRL 90082302,2003
Near
Lowering the trigger threshold increases the
near-side jet correlation strength
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Going down to 62 GeV Inclusive Spectra
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RCP and RAA at 62 GeV
Inclusive spectra of charged particles and ?0
are suppressed in central collisions relative to
the scaled peripheral AuAu and pp collisions
What to expect from di-hadron measurements at 62
GeV?
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Di-hadron azimuthal correlations in Pythia

• Pythia 6.131, pp at 200 and 62 GeV
• Kinematic selection CKIN(3)4.0 GeV
• -minimum pt for hard 2?2 processes
• Initial state radiation on/off
• Final state radiation on/off
• Primordial kt1GeV on/off

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Parton spectra in pp at 200 and 62 GeV
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT0
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Di-hadron azimuthal distributions

• ?,?-,K,K-,p,pbar only, ?lt0.9
• pTtrig4-6 GeV/c, 2 GeV/cltpTassoltpTtrig

Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT0
Near-side peak is suppressed by about a factor
of 3
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Near and away side parton pt-distributions
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT0
NEAR
Near - ??lt?/2 Away- ??-?lt?/2
NEAR ltpTgt11.4 GeV/c ltpTgt 9.2
GeV/c AWAY ltpTgt 9.2 GeV/c ltpTgt
7.0 GeV/c
AWAY
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Suppression of near-side from parton spectra
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT0
Yield ratio ltNeargt/ltawaygt0.3 _at_200 GeV
0.1 _at_62 GeV
Factor of 3!
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KT- effect on the di-hadron distribution
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT0
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KT- effect on the di-hadron distribution
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS0,KT1
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Final State radiation effect
Pythia 6.131 pp 200 GeV pp 62 GeV IS0,FS1,KT0
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Initial State radiation effect
Pythia 6.131 pp 200 GeV pp 62 GeV IS1,FS0,KT0
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All effects combined
Pythia 6.131 pp 200 GeV pp 62 GeV IS1,FS1,KT1
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pp-reference at 62 GeV
pt triggergt2.5 GeV/c, pt associatedgt1.0 GeV/c
pt trig, asso may be too low for comparison with
AuAu
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What to expect in Au-Au at 62 GeV?

• Much weaker near-side correlations than for Au-Au
  at 200 GeV
• Similar strength of away-side correlations in
  peripheral collisions at both energies
• Away-side peak should still be suppressed in
  central Au-Au collisions at 62 GeV
• Measurements are much more statistics hungry but
  youll see it very soon -)