STAR STAR Back-to-Back Di-Jet Back-to-Back Di-Jet Triggered Multi- Triggered Multi- Hadron Correlations Hadron Correlations as Medium Probes in as Medium Probes in STAR STAR Olga Barannikova University of Illinois at Chicago for the STAR Collaboration Physics motivations Data analysis: Results: Summary di-jet events background subtraction correlations in d+Au and Au+Au interpretations
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STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium Probes in STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium.
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Difference in associated yield Di-triggers sample higher energy jets
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 13 / 19
STARSTAR
One high-pT trigger only: Away-side modification.
Di-jet trigger: jet peaks on both near and away side!
Preliminary result: central Au+AuPreliminary result: central Au+Au
T1: pT>5 GeV/c, T2: pT>4 GeV/c, A: pT>1.5 GeV/c
Di-jet trigger
T2
A1
T1
Single trigger
A1
T2
T2A1_T1
T2A1
-1-2 0 1 2 3 4 5
2
0 1
_d
N_
Ntr
ig d
)
-2
4
STAR Preliminary
200 GeV ZDC central 12%
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 14 / 19
STARSTAR Au+Au vs d+Au comparisonAu+Au vs d+Au comparison
T1A1_T2
T2A1_T1
-1-2 0 1 2 3 4 5
2
0 1
_d
N_
Ntr
ig d
)
STAR Preliminary
200 GeV Au+Au, 12% central
Di-jets are suppressed. Once select di-jets, away-side associated particles NOT suppressed. Shapes of near- and away-sides similar. Central Au+Au ~ d+Au.
No energy loss for triggered di-jets!Tangential di-jets (or punch-through without interactions).
T1: pT>5 GeV/c, T2: pT>4 GeV/c, A: pT>1.5 GeV/c
Au+Au
d+Au
-1-2 0 1 2 3 4 5
1
0
1
_d
N_
Ntr
ig d
)
STAR Preliminary
2
3
200 GeV Au+Au & d+Au
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 15 / 19
Di-jet triggered correlations: near-side ~ away-side no significant modifications? no associated particle suppression?
~10% Centrality
-1-2 0 1 2 3 4 5
1
_d
N_
Ntr
ig d
)
2
STAR Preliminary
0
4
T2A1
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 19 / 19
STARSTAR
Summary:Summary:
New analysis of 2+1 correlations:Events triggered with 2 high-pT particles (T1: pT>5 GeV/c, T2: pT>4 GeV/c) and look at a third, associated particle (A1: pT>1,5 GeV/c).
Preliminary results show a di-jet structure, with no modification of associated particles tangential jets, or punch-through without interactions.
New technique allows further exploration of the “surface bias”, and will probe the medium in a more controlled way.
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 20 / 19
STARSTAR Au+Au vs d+Au comparisonAu+Au vs d+Au comparison
T1A1_T2
T2A1_T1
-1-2 0 1 2 3 4 5
2
0 1
_d
N_
Ntr
ig d
)
STAR Preliminary
200 GeV Au+Au, 12% central
sameaway
sameaway
Au+Au
d+Au
-1-2 0 1 2 3 4 5
1
0
1
_d
N_
Ntr
ig d
)
STAR Preliminary
2
3
200 GeV Au+Au & d+Au
Di-jets are suppressed. Once select di-jets, away-side associated
particles NOT suppressed. Shapes of near- and away-sides similar. Central Au+Au ~ d+Au.
No energy loss for triggered di-jets!
Tangential di-jets (or punch-through without interactions).
T1: pT>5 GeV/c, T2: pT>4 GeV/c, A: pT>1.5 GeV/c
Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 21 / 19
STARSTAR
STAR Preliminary **
Surface effectSurface effect
T1: pT>5GeV/c
T2: pT>4GeV/c
A: pT>1.5GeV/c
If the triggers have tangential bias: expect a term related to the surface
Surface ~ R2 ~ Npart2/3
** Shown are statistical errors only
Number of triggers per event (per number of binary collisions)
Single triggers and (all qualified) pairs behave similar to inclusives