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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 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

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  1. 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

  2. Df Total Elliptic flow C(Df) 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. Cu+Cu @ 200 GeV Au+Au @ 62.4 GeV Different Colliding Systems and Energies Au+Au @ 200 GeV N Grau

  13. assoc D trigg D assoc 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

  14. 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

  15. Shape independent of RP orientation Au+Au Reaction Plane Dependence (II) Know v2 depending on triggers RP orientation. N Grau

  16. Au+Au Reaction Plane Dependence At Higher pT • No hint of a volcano shape in any RP bin N Grau

  17. g Hadrons 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

  18. C(Df) C(Df) Df Df 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

  19. 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

  20. 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

  21. For the future: Non-Photonic e-h Use jet correlations to further understand heavy quark energy loss. N Grau

  22. 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

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