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Jet Correlations from PHENIX

• Focus entirely on A+A collisions• High-trigger pT correlations

– Can we do jet tomography?

• Low-trigger pT correlations– Away-side shape modification– RP dependence

• An outlook– Direct -h correlations, non-photonic e-h correlations

Nathan Grau, Columbia University, Nevis Labs

For the PHENIX Collaboration

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ConstructingJet Correlations

ddN

ddNC

d

dN

N mix

realpairs

trig /

/1

Mixed events – corrects pair acceptance

Hard scattering Resonance decays

(rad)

Elliptic flowTotal

C(

)

Sum over all events jets measured on a statistical basis

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Jet Quenching

• Single particle suppression pattern persists to 20 GeV• Moderate pT jets are suppressed• Due to energy loss of partons in the medium

Pedestal&flow subtracted

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Away-Side Jet in Au+Au!

• C() 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

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Clear Away Side in Cu+Cu!

• Larger jet S/B in central Cu+Cu than central Au+Au

• v2 modulation is smaller as well

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Lack of Away-Side Broadening

8 < pT(trig) < 15 GeV/c

Widths do not change between p+p and Au+Au?!?

Trigger 5-10 GeV/c

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Expected Broadening of Away Side

Able to fit IAA from STAR.Red – gluons from energy loss.

Black – scattering of parent partons

I. Vitev hep-ph/0501255

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Away Side Yield Suppression

• Away-side yield is suppressed?!?

• What mechanism can suppress yields without broadening them?– Tangential jets?

– Punch through?

8 < pT(trig) < 15 GeV/c

D. Magestro QM2005

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Punch-through Events (I)

• Monte Carlo includes radial expansion reducing the effect of E ~ L2

• Non-zero probability to lose no energy

• Does the away side carry away any information from the interior of the collision zone?

Production vertices of events with trigger > 8 GeV

Red circles indicate an associated hadron (> 4 GeV) suffering no E-loss

T. Renk hep-ph/0602045

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Punch-through Events (II)

• Yield suppression sensitive to the probability of punch-through

• Lower pT pairs are apparently more sensitive to energy loss…

Comparison of MC to STAR away-side yields.

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Lower pT Correlations

• h-h Correlations in Au+Au (upper plots)– C() strength ~ jet S/B– Few % S/B at lowest pT Correlations.

• h-h Correlations with background subtracted (lower plots)

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Different Colliding Systems and Energies

Au+Au @ 200 GeV

Cu+Cu @ 200 GeV

Au+Au @ 62.4 GeV

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Parameterize the Away-Side Shape

trigg

assoc

D

Dassoc

Parameterize the away-side shape as a double Gaussian that are offset symmetrically around = by fit parameter D.

Could be a “bent” jet or a mach/ Cherenkov cone

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Au+Au Reaction Plane Dependence (I)

Look at 4th bin since it has the smallest v2.

Dip exists at most central before substraction!

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Au+Au Reaction Plane Dependence (II)

Know v2 depending on triggers RP orientation.

Shape independent of RP orientation

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Au+Au Reaction Plane Dependence At Higher pT

• No hint of a volcano shape in any RP bin

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For the future: Direct -h

• 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

Hadrons

gqq

qqg

PRL 94 232301 (2005)

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Inclusive -h Correlations in Au+Au

C

(

C(

: 5-10 GeV/ch: 1-2 GeV/c

Comparison with 0 triggered data necessary to extract direct photon correlations.

: 5-10 GeV/ch: 3-5 GeV/c

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Comparison of - and 0- Triggered Widths

Near-side widths are consistent between -triggered and 0-triggered.

Dominant inclusive photon correlation is decay from jet fragments

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-h Near Side Yields

PRL 94 232301 (2005)

~50% direct photons above 5 GeV/c in the most central.

Also seen in -triggered near side yield ratio to 0 -triggered yield.

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For the future: Non-Photonic e-h

Use jet correlations to further understand heavy quark energy loss.

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Summary and Conclusions

• High-pT triggered correlations show– Au+Au away-side that is not broadened– A suppressed yield consistent with punch-through jets.– What is learned from these correlations then?

• 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– Further RP studies: Can we show E ~ L2,Ln?– Direct -h: D(z) modification– e-h Correlations: Heavy quark energy loss