What do we Learn From Azimuthal Correlation Measurements in PHENIX

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

2. A Cue from Lattice QCD: Phase Transition Motivation Probes that indicate equilibrated nuclear matter with ε > 1 GeV/fm3 are of particular Interest

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

4. What Information do Correlation Measurements Provide ? • Reliable Pressure Estimates: • Thermalization • Opacity of the Medium • EOS • 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 Simultaneous Study of Harmonic and Jet Correlations is Crucial

5. PRL87, 052301 (2001) Extrapolation From ET Distributions time to thermalize the system (t0 ~ 0.2 - 1 fm/c) eBjorken~ 5 - 15 GeV/fm3 ~ 35 – 100 ε0 Substantial Energy Energy Density Created at RHIC ! peripheral collisions Central collisions The Energy Density is Well Above the Predicted Value for the Phase Transition !

6. Extrapolation From ET Distributions time to thermalize the system (t0 ~ 0.2 - 1 fm/c) A Reliable Pressure Measurement gives Insight:  Elliptic Flow eBjorken~ 5 - 15 GeV/fm3 Is the Energy Thermalized ?

7. PHENIX PRELIMINARY PHENIX PRELIMINARY Correlation Functions Substantial Signals Attributable to Flow and Jets are observed ?

8. phenix preliminary nucl-ex/0305013 V2 data Substantial Signals Atributable to Flow are observed ? Indicative of Early Themalization - Large Pressures, Jets correlate with RP

9. Energy Dependence v2 apparently Saturates Are we in the v2 plateau ?

10. Comparison with results from SPS

11. Hydro Limit How Large is the Pressure ? Scaling Tests • Very Large Pressure Gradients Non Trivial !!  Scaling not Incompatible with Recombination

12. Hydro Limit Molnar et al. Is the Opacity Large ? • Scaled v2 should give similar values !!

13. PHENIX Preliminary Is the Opacity Large ? • Scaled v2 compatible with large Opacities

14. Observable Jet Correlations • Remarkable Probes for High-density Matter • Auto-Generated on the right time-scale Operational Strategy A+A p+p d+A

15. Fragmentation: away-side near-side Jet Correlations parton hadron hadron parton Azimuthal Correlations Carry Invaluable Information about the di-jet.

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

17. Observable Jet Correlations Operational Strategy A+A p+p d+A

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

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

20. pp d+Au |jTy| similar to that for pp – No Surprise !!

21. I.Vitev nucl-th/0306039 I.Vitev d+Au No significant kT-broadening seen in dAu data

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

23. Calibrated Signal Expected Yield Dependence

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

25. q q Centrality Dependence of conditional Jet yields Escaping Jet “Near Side” Suppressed Jet “Away Side” • Charged hadron yields show apparent away-side suppression ?

26. Trigger Hadron Trigger Baryon Trigger Meson Associated Mesons Associated Baryons Associated Hadrons Flavor Composition of Jets in Au + Au Several Trigger Requirements have been exploited

27. Flavor Composition of Jets in Au + Au Associated Mesons PHENIX Preliminary Associated Baryons Correlation Functions for associated Baryons are Dominated by Harmonic Contributions

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

29. Baryon to Meson Ratio for Away-side Jet The Observed baryon to meson ratio is higher for away-side jets

30. Story is different !!

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

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

36. High Density partonic material formed leading particle d + Au q q leading particle 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 pTRef • v2 Factorization • ~ Eccentricity Scaling of v2 for high pT • Away-side Jet suppression in central collisions • Suppression Dependence on Orientation • Modification of Jet Properties