1. What do we Learn From Azimuthal Correlation Measurements in PHENIX Roy. A. Lacey Nuclear Chemistry, SUNY, Stony Brook

2. R. Lacey, SUNY Stony Brook A Cue from Lattice QCD: Phase Transition Probes that indicate equilibrated nuclear matter with ε > 1 GeV/fm 3 are of particular Interest MotivationMotivation

3. R. Lacey, SUNY Stony Brook In-plane Out-of-plane Correlation Function Harmonic Jet Function Azimuthal Correlations Provide Direct Access to the Properties of the High Energy Density Matter Created at RHIC Why is the Correlation Probe Compelling ? Why is the Correlation Probe Compelling ? Azimuthal Correlations are derived from Harmonic and di-jet contributions

4. R. Lacey, SUNY Stony Brook What Information do Correlation Measurements Provide ? A Direct Route for the Study of Jets Characterization of Jet Topologies in pp, dA & AA Quantification of Medium Induced Modifications to Topologies  Crucial for study of the properties of the medium Tomographic Imaging of Hot and Dense Partonic Matter Reliable Pressure Estimates: Thermalization Opacity of the Medium EOS Simultaneous Study of Harmonic and Jet Correlations is Crucial

5. R. Lacey, SUNY Stony Brook The Energy Density is Well Above the Predicted Value for the Phase Transition ! Substantial Energy Energy Density Created at RHIC ! Substantial Energy Energy Density Created at RHIC ! PRL87, 052301 (2001) Central collisions peripheral collisions time to thermalize the system (  0 ~ 0.2 - 1 fm/c)  Bjorken  ~ 5 - 15 GeV/fm 3 ~ 35 – 100 ε 0 Extrapolation From E T Distributions

6. R. Lacey, SUNY Stony Brook time to thermalize the system (  0 ~ 0.2 - 1 fm/c)  Bjorken  ~ 5 - 15 GeV/fm 3 Extrapolation From E T Distributions Is the Energy Thermalized ? Is the Energy Thermalized ? A Reliable Pressure Measurement gives Insight:  Elliptic Flow

7. R. Lacey, SUNY Stony Brook Correlation Functions Substantial Signals Attributable to Flow and Jets are observed ? PHENIX PRELIMINARY

8. R. Lacey, SUNY Stony Brook V 2 data Substantial Signals Atributable to Flow are observed ? Indicative of Early Themalization -  Large Pressures, Jets correlate with RP phenix preliminary nucl-ex/0305013

9. R. Lacey, SUNY Stony Brook v2 apparently Saturates Are we in the v2 plateau ? Energy Dependence

10. R. Lacey, SUNY Stony Brook Comparison with results from SPS

11. R. Lacey, SUNY Stony Brook  Very Large Pressure Gradients Non Trivial !!  Scaling not Incompatible with Recombination Scaling Tests How Large is the Pressure ? How Large is the Pressure ? Hydro Limit

12. R. Lacey, SUNY Stony Brook  Scaled v2 should give similar values !! Is the Opacity Large ? Is the Opacity Large ? Hydro Limit Molnar et al.

13. R. Lacey, SUNY Stony Brook  Scaled v2 compatible with large Opacities Is the Opacity Large ? Is the Opacity Large ? PHENIX Preliminary

14. R. Lacey, SUNY Stony Brook Jet Correlations p+p d+A A+A Remarkable Probes for High-density Matter Auto-Generated on the right time-scale Operational Strategy Observable

15. R. Lacey, SUNY Stony Brook near-side away-side hadron parton Jet Correlations Jet Correlations Fragmentation : Azimuthal Correlations Carry Invaluable Information about the di-jet Azimuthal Correlations Carry Invaluable Information about the di-jet.

16. R. Lacey, SUNY Stony Brook Fragmentation : The Predicted Influence of the Medium is Specific The Predicted Influence of the Medium is Specific. Jets in Au+Au Collisions Jets in Au+Au Collisions Induced Gluon Radiation ~ collinear  gluons in cone “Softened” fragmentation I. Vitev, nucl-th/0308028 Gyulassy et al., nucl-th/0302077

17. R. Lacey, SUNY Stony Brook Jet Correlations p+p d+A A+A Operational Strategy Observable

18. R. Lacey, SUNY Stony Brook pp and dAu correlation functions 3.0<p T <6.0 p+p h +- d+Au Away side peak d+Au    h  1.0<p T <1.5 1.5<p T <2.0 Fit = const + Gauss(0)+Gauss(  ) Jet function assumed to be Gaussian Fixed correlations Fixed correlations: 5.0<p Ttrigg <16.0 GeV/c Assorted correlations Assorted correlations: Distinct Di-jet peaks

19. R. Lacey, SUNY Stony Brook  N,  A  |j Ty | ,  |k Ty |  in p+p PHENIX preliminary  |j Ty |  = 359  11 MeV/c  |k Ty |  = 964  49 MeV/c PHENIX preliminary  |j Ty |  = 359  11 MeV/c  |k Ty |  = 964  49 MeV/c  |j Ty |  and  |k Ty |  in good agreement with prior measurements: PLB97 (1980)163 PRD 59 (1999) 074007 AA PHENIX preliminary

20. R. Lacey, SUNY Stony Brook d+Au  |j Ty |  similar to that for pp – No Surprise !! pp

21. R. Lacey, SUNY Stony Brook d+Au No significant k T -broadening seen in dAu data I.Vitev I.Vitev nucl-th/0306039

22. R. Lacey, SUNY Stony Brook Area under curve Total Area fraction of pairs that are correl. jet pairs correlated jet-pairs over combinatoric background conditional yields are corrected for  -acceptance & efficiency, and are reported in the PHENIX  -acceptance ( |  | < 0.35 ). Conditional-Yields Conditional-Yields

23. R. Lacey, SUNY Stony Brook Calibrated Signal Calibrated Signal Expected Yield Dependence

24. R. Lacey, SUNY Stony Brook Fragmentation : Is the Away-side Jet Broadened in Au+ Au Collisions ? Is the Away-side Jet Broadened in Au+ Au Collisions ? Associated charged hadrons and mesons show centrality dependent broadening of away-side jet  Modification d+Au

25. R. Lacey, SUNY Stony Brook Centrality Dependence of conditional Jet yields Charged hadron yields show apparent away-side suppression ? Charged hadron yields show apparent away-side suppression ? Escaping Jet “Near Side” Suppressed Jet “Away Side” q q

26. R. Lacey, SUNY Stony Brook Several Trigger Requirements have been exploited Flavor Composition of Jets in Au + Au Flavor Composition of Jets in Au + Au AssociatedMesonsAssociatedBaryons Trigger Hadron Trigger Baryon Trigger Meson AssociatedHadrons

27. R. Lacey, SUNY Stony Brook AssociatedMesons PHENIX Preliminary AssociatedBaryons Correlation Functions for associated Baryons are Dominated by Harmonic Contributions Flavor Composition of Jets in Au + Au Flavor Composition of Jets in Au + Au

28. R. Lacey, SUNY Stony Brook Centrality Dependence of conditional Jet yields Charged hadron yields show apparent away-side suppression Charged hadron yields show apparent away-side suppression Hadron yields dominated by Mesons Hadron yields dominated by Mesons Similar near- and away-side for associated baryons. Similar near- and away-side for associated baryons. Escaping Jet “Near Side” Suppressed Jet “Away Side” q q

29. R. Lacey, SUNY Stony Brook The Observed baryon to meson ratio is higher for away-side jets Baryon to Meson Ratio for Away-side Jet

30. R. Lacey, SUNY Stony Brook Story is different !!

31. R. Lacey, SUNY Stony Brook High energy-density matter is created at RHIC. Correlation measurements Suggests a State of Matter Correlation measurements Suggests a State of Matter not heretofore seen Pressure Gradients Develop in Partonic matter -> elliptic flow -> v2 Au+Au Collisions at RHIC High Density Thermalized partonic material formed Early Hard Scattered Partons Traverse partonic material  Jet-quenching (early) & v2  Jet-quenching (early) & v2 q q leadingparticle d + Auleadingparticle Expansion followed by Hadronization

32. R. Lacey, SUNY Stony Brook

35. In-plane Out-plane X.N. Wang Angular Dependent Jet Modification should be an Important Observable Di-Jet Tomography: The Next Frontier

36. R. Lacey, SUNY Stony Brook High Density partonic material formed q q leadingparticle d + Auleadingparticle Jet Quenching and Flow have a common denominator (eccentricity) Expectations:  Evidence for High Energy-Density  Evidence for Quenching  High & low pT particles correlated  v2 essentially independent of pT Ref  v2 Factorization  ~ Eccentricity Scaling of v2 for high pT  Away-side Jet suppression in central collisions  Suppression Dependence on Orientation  Modification of Jet Properties