1. Jet Correlations from PHENIX: From Low-pT to High-pT
Nathan Grau, Columbia University, Nevis Labs
For the PHENIX Collaboration
Focus entirely on A+A collisions
High-trigger pT correlations
Can we do jet tomography?
What does theory tell us?
Low-trigger pT correlations
Away-side shape modification
RP dependence
Many thanks to Paul Constantin, Wolf Holzmann, Jiangyong Jia, Jiamin Jin, and Hua Pei for work I’m showing.
Also thanks to Brian Cole, Barbara Jacak, Craig Ogilvie, Paul Stankus, and Mike Tannenbaum for useful discussions.
Correlations and Fluctuations
N.Grau 07/07/06

2. Correlations and Fluctuations
Jet Quenching
nucl-ex/
Moderate pT jets are suppressed
Pedestal&flow subtracted
STAR PRL 91, (2003)
Lower pT jets are suppressed and broadened
nucl-ex/ accepted
Single particle suppression pattern persists to 20 GeV
Correlations and Fluctuations
N.Grau 07/07/06

3. Constructing Jet CorrelationsDf
Mixed events – corrects pair acceptance
Hard scattering
Resonance decays
Df (rad)
Elliptic flow
Total
C(Df)
Sum over all events  jets measured on a statistical basis
Correlations and Fluctuations
N.Grau 07/07/06

4. High-pT Jet Correlations
Correlations and Fluctuations
N.Grau 07/07/06

5. Correlations and Fluctuations
Away-Side Jet in Au+Au!
C(Df) strength ~ S/B of jets
Red and blue lines are the uncertainty in v2
Jets seen above the background for trigger >5 GeV/c and associated >2 GeV/c
Correlations and Fluctuations
N.Grau 07/07/06

6. Clear Away-Side in Cu+Cu!
Larger jet S/B in central Cu+Cu than central Au+Au
v2 modulation is smaller as well
Correlations and Fluctuations
N.Grau 07/07/06

7. Away-Side Yield Suppression
PHENIX
8 < pT(trig) < 15 GeV/c
h-h correlations in Au+Au
Near-side unmodified
Away-side yield is suppressed!
nucl-ex/
J. Jia Hard Probes 2006
Correlations and Fluctuations
N.Grau 07/07/06

8. Expected Broadening of Away-Side
I. Vitev hep-ph/
Consequence of energy loss is broadening of the away-side correlations
multiple scattering of the parton
gluon radiation
Red – gluons from energy loss.
Black – scattering of parent partons
Correlations and Fluctuations
N.Grau 07/07/06

9. Lack of Away-Side Broadening!
D. Magestro QM2005
8 < pT(trig) < 15 GeV/c
Trigger 5-10 GeV/c
Widths do not change between p+p and Au+Au?!?
Correlations and Fluctuations
N.Grau 07/07/06

10. Punch-through Events (I)
T. Renk hep-ph/
Monte Carlo includes radial expansion reducing the effect of DE ~ L2
Non-zero probability to lose no energy
Away-side only sensitive to none-zero energy loss?
Production vertices of events with trigger > 8 GeV
Red circles indicate an associated hadron (> 4 GeV) suffering no E-loss
Correlations and Fluctuations
N.Grau 07/07/06

11. Punch-through Events (II)
Comparison of MC to STAR away-side yields.
Yield suppression sensitive to the probability of punch-through
Correlations and Fluctuations
N.Grau 07/07/06

12. Non-zero Probability for E-loss
Important quantitative question not answered by theorists:
ASW
qhat = 15 GeV/fm2 and L=2
P(0) ~30-40%!
GLV
P(0) ~ 0%!
Can these data help constrain this result?
Weidemann, Vitev Hard Probes 2006
Correlations and Fluctuations
N.Grau 07/07/06

13. Correlations and Fluctuations
Lower pT Correlations
h-h Correlations in Au+Au (upper plots)
C(Df) strength ~ jet S/B
Few % S/B at lowest pT Correlations.
h-h Correlations with background subtracted (lower plots)
Correlations and Fluctuations
N.Grau 07/07/06

14. Different Colliding Systems and Energies
200 GeV
GeV
200 GeV
Correlations and Fluctuations
N.Grau 07/07/06

15. Parameterize the Away-Side Shape
trigg
assoc D D
assoc
Could be a “bent” jet or a mach/ Cherenkov cone
Parameterize the away-side shape as a double Gaussian that are offset symmetrically around Df = p by fit parameter D.
Correlations and Fluctuations
N.Grau 07/07/06

16. Physical Mechanism of the Away-Side Structure
Deflection due to flowing medium
Sensitive to jet + bulk interaction
hep-ph/ , Armesto, Salgado, Wiedemann
Shoulder position dependent on the RP orientation.
Cones
Mach cones
measure speed of sound
nucl-th/ Stoecker, hep-ph/ Muller, Ruppert, hep-ph/ (2004) Casalderrey-Solana, Shuryak, Teaney
Cerenkov Cones
measure index of refraction
nucl-th/ Koch, Majumder, Wang
Both would conclude shoulder position independent of RP orientation.
Distinguish by pT dependence to the shape.
Do we understand the root-s and system size evolution?
Correlations and Fluctuations
N.Grau 07/07/06

17. Au+Au Reaction Plane Dependence (I)
Look at 4th bin since it has the smallest v2.
Dip exists at most central before substraction!
Correlations and Fluctuations
N.Grau 07/07/06

18. Au+Au Reaction Plane Dependence (II)
Know v2 depending on triggers RP orientation.
J. Bielcikova et al, Phys. Rev. C69:021901, 2004
Correlations and Fluctuations
N.Grau 07/07/06

19. Mach Cones in From Theory
Mach shocks do not produce the two-particle correlation structure?
Hydro calculation of energy lost by jets
Remnant jet
Backsplash
U. Heinz HP2006
Correlations and Fluctuations
N.Grau 07/07/06

20. For the future: 3-Particle Correlations (I)
3-particle correlations = 3 jet + 2 jetx1 thermal + 1 jetx2 thermal + 3 thermal.
Determining background is difficult
3 jet correlation signal-to-background worse than 2 jet correlation signal-to-background
Looking for few % effect.
Correlations and Fluctuations
N.Grau 07/07/06

21. For the future: 3-Particle Correlations (II)
High pT (2.5<pT<4) p1
p2-a
p3-a
Correlation Variables :
Study the 3-particle correlations in the “high-pT reference frame”
Project associated particles to perpendicular plane
(1<pT<2.5)
Correlations and Fluctuations
N.Grau 07/07/06

22. For the future: 3-Particle Correlations (III)
θ* = 120
θ* = 60
θ* = 180
v2 subtracted Correlation Function
θ* = 120
θ* = 60
θ* = 180
PHENIX Preliminary
20-40 %
Correlations and Fluctuations
N.Grau 07/07/06

23. For the future: Direct g-h
PRL (2005) g
Hadrons
Direct photons not suppressed in the medium.
Much less “trigger bias” i.e. less biased toward skin emission
Photon measures jet energy  measured away-side D(z) modification
Correlations and Fluctuations
N.Grau 07/07/06

24. Inclusive g-h Correlations in Au+Au
C(Df) Df Df
C(Df)
g: 5-10 GeV/c
h: 1-2 GeV/c
g: 5-10 GeV/c
h: 3-5 GeV/c
Comparison with p0 triggered data necessary to extract direct photon correlations.
NB: a dip at p exists in the left CF after subtraction
Correlations and Fluctuations
N.Grau 07/07/06

25. Summary of pT Evolution
h± --- h± p0 --- h±
C: 0-20% 1 2 3 4 5 6 7 8
PT Partner
PT Trigger
The jet functions in Au+Au collisions evolve with both partner and trigger pT
Away-side peak visible
Away-side shoulders visible
Neither visible
Based on PHENIX preliminary
and nucl-ex/
P. Stankus CIPANP06
Correlations and Fluctuations
N.Grau 07/07/06

26. Summary and Conclusions
High-pT triggered correlations show
Au+Au away-side not broadened
A suppressed away-side yield consistent with punch-through jets.
What is learned about the medium from this data?
Low-pT triggered correlations show a strongly modified away-side shape
independent of system size and collision energy
Independent of trigger orientation to the RP
Still left to do with current data
Three particle correlations: Sorting out deflected, vs. mach/cerenkov
Further RP studies: Can we show DE ~ L2,L,Ln?
Direct g-h: D(z) modification
Correlations and Fluctuations
N.Grau 07/07/06

27. Correlations and Fluctuations
Backup
Correlations and Fluctuations
N.Grau 07/07/06

28. Comparison of g- and p0- Triggered Widths
Near-side widths are consistent between g-triggered and p0-triggered.
Dominant inclusive photon correlation is decay from jet fragments
Correlations and Fluctuations
N.Grau 07/07/06

29. Correlations and Fluctuations
g-h Near Side Yields
PRL (2005)
~50% direct photons above 5 GeV/c in the most central.
Also seen in g-triggered near side yield ratio to p0 -triggered yield.
Correlations and Fluctuations
N.Grau 07/07/06

30. For the future: RP-Dependence At Higher pT
Qualitatively: No hint of a volcano shape in any RP bin
Correlations and Fluctuations
N.Grau 07/07/06