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Jet Correlations from PHENIX. Nathan Grau, Columbia University, Nevis Labs For the PHENIX Collaboration. Focus entirely on A+A collisions High-trigger p T correlations Can we do jet tomography? Low-trigger p T correlations Away-side shape modification RP dependence An outlook

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Jet correlations from phenix
Jet Correlations from PHENIX

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?

  • Low-trigger pT correlations

    • Away-side shape modification

    • RP dependence

  • An outlook

    • Direct g-h correlations, non-photonic e-h correlations

N Grau

Constructing jet correlations



Elliptic flow


Hard scattering

Resonance decays

Df (rad)

ConstructingJet Correlations

Mixed events – corrects pair acceptance

Sum over all events  jets measured on a statistical basis

N Grau

Jet quenching

Pedestal&flow subtracted

Jet Quenching

  • Single particle suppression pattern persists to 20 GeV

  • Moderate pT jets are suppressed

  • Due to energy loss of partons in the medium

N Grau

Away side jet in au au
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

N Grau

Clear away side in cu cu
Clear Away Side in Cu+Cu!

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

  • v2 modulation is smaller as well

N Grau

Lack of away side broadening

8 < pT(trig) < 15 GeV/c

Lack of Away-Side Broadening

Trigger 5-10 GeV/c

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

N Grau

Expected broadening of away side

Black – scattering of parent partons

Red – gluons from energy loss.

Expected Broadening of Away Side

I. Vitev hep-ph/0501255

Able to fit IAA from STAR.

N Grau

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

Away Side Yield Suppression

D. Magestro QM2005

N Grau

Punch through events i
Punch-through Events (I)

T. Renk hep-ph/0602045

  • Monte Carlo includes radial expansion reducing the effect of DE ~ 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

N Grau

Punch through events ii
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.

N Grau

Lower p t correlations
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)

N Grau

Different colliding systems and energies

Cu+Cu @ 200 GeV

Au+Au @ 62.4 GeV

Different Colliding Systems and Energies

Au+Au @ 200 GeV

N Grau

Parameterize the away side shape






Parameterize the Away-Side Shape

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.

N Grau

Au au reaction plane dependence i
Au+Au Reaction Plane Dependence (I)

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

Dip exists at most central before substraction!

N Grau

Au au reaction plane dependence ii

Shape independent of RP orientation

Au+Au Reaction Plane Dependence (II)

Know v2 depending on triggers RP orientation.

N Grau

Au au reaction plane dependence at higher pt
Au+Au Reaction Plane Dependence At Higher pT

  • No hint of a volcano shape in any RP bin

N Grau

For the future direct g h



For the future: Direct g-h

PRL 94 232301 (2005)

  • 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

N Grau

Inclusive g h correlations in au au





Inclusive g-h Correlations in Au+Au

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.

N Grau

Comparison of g and p 0 triggered widths
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

N Grau

G h near side yields

PRL 94 232301 (2005)

g-h Near Side Yields

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

Also seen in g-triggered near side yield ratio to p0 -triggered yield.

N Grau

For the future non photonic e h
For the future: Non-Photonic e-h

Use jet correlations to further understand heavy quark energy loss.

N Grau

Summary and conclusions
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 DE ~ L2,Ln?

    • Direct g-h: D(z) modification

    • e-h Correlations: Heavy quark energy loss

N Grau