Multi-Particle Azimuthal Correlations at RHIC !!

1. Multi-Particle Azimuthal Correlations at RHIC !! What do they tell us about Possible Quenching? Roy A. Lacey USB - Chem (SUNY Stony Brook)

2. Outline • Motivation • General • Specific • Correlation Technique • Assorted-pT method • Fixed-pT method • Advantages of the Methods • Correlation Results • - Compatible with Jets, Flow, etc. ? • - What have we learned ? See W. Holzman’s Poster Roy A. Lacey HIC03

3. Today’s Cold Universe Motivation - General The Big Picture What can we learn from experiments about this past history? Roy A. Lacey HIC03

4. schematic view of jet production leading particle hadrons q q hadrons • Jets: • Primarily from gluons at RHIC • Sensitive to the QCD medium (dE/dx) • Flow: • Primarily from pressure build-up • Reflect conditions in collision zone (EOS) • CGC: • Provides insights on Saturation Physics leading particle Motivation - Why Study Correlations Correlation Studies can provide information on the particle production mechanism,the EOS, Initial State effects, QGP formation…. (Very Important Signal) Roy A. Lacey HIC03

5. Reminder - Single Particle Distributions Au + Au Experiment d + Au Control Experiment Striking difference between d+Au and Au+Au results. • Cronin effect dominate in d+Au • High-pT Jet Suppression dominate in Au+Au. Final Data Preliminary Data Roy A. Lacey HIC03

6. y x What Insights do Correlation Measurements Provide ?? Energy loss can result in an anisotropy which can serve as a probe of the medium Roy A. Lacey HIC03

7. STAR @ 200 GeV y x V2 from calculations which assume quenching The Problem B. Muller nucl-th/0208038 Extreme Quenching not Sufficient to Account for Observed Npart Dependence of V2 Roy A. Lacey HIC03

8. Study Correlation • Functions: • Uncertainties associated with Acceptance, efficiency, etc Reduced (STAR) Wang et al., PRC 44, 1091 (1991) Lacey et al. PRL 70, 1224 (1993) Au+Au ??? Measure Distributions PHENIX uses an Azimuthally Asymmetric Detector Measuring Azimuthal Correlations Roy A. Lacey HIC03

9. First Application of the Azimuthal Correlation Technique at RHIC Constructing Correlation Functions Wang et al., PRC 44, 1091 (1991) Lacey et al. PRL 70, 1224 (1993) Roy A. Lacey HIC03

10. Asymmetry ( ) Anisotropy ( ) Approach - 1 Definition Azimuthal Distributions and Correlation Functions are Characterized by an Anisotropy and an Asymmetry. Roy A. Lacey HIC03

11. Saturation Model Mini-Jets, lead to strong anisotropy and an asymmetry Information in Correlation Functions HIJING Hydro or Transport With large Opacity Flow leads to strong anisotropy – no asymmetry Jets lead to strong anisotropy and an asymmetry • The anisotropy of the correlation function can reflect • both flow and Jet contribution • The Asymmetry provides crucial Jet Information Roy A. Lacey HIC03

12. Extracting v2 via Fixed Correlations v2 characterize the Anisotropy pT Roy A. Lacey HIC03

13. Extracting v2 via Assorted Correlations pT Reference pT Roy A. Lacey HIC03

14. PHENIX Preliminary d+Au Assorted-pT Correlation Functions Di-jet structure develops with increasing pT Roy A. Lacey HIC03

15. d+Au Au+Au Min Bias 60-90% Comparison of d+Au and Au+Au ` Peripheral Au+Au is essentially identical d+Au Roy A. Lacey HIC03

16. Escaping Jet “Near Side” d+Au Au+Au Min Bias 0-5% Suppressed Jet “Away Side” Comparison of d+Au and Au+Au Apparent “away-side suppression Roy A. Lacey HIC03

17. d+Au Au+Au Min Bias 20- 40% Comparison of d+Au and Au+Au Mid-Central events indicate sizeable harmonic contributions Roy A. Lacey HIC03

18. Comparison of 130 and 200 GeV Results PHENIX Preliminary Anisotropy (v2) essentially identical Roy A. Lacey HIC03

19. Differential v2 Minimum Bias Model performance depend on pT range  All models Require Humongous Energy Densities Roy A. Lacey HIC03

20. Centrality Dependence of v2 • Different Models predict different scaling • behavior for the centrality dependence of v2 • Hydro/Molnar --- eccentricity scaling • Minijet – Overlap Area scaling eccentricity y x It is important to test for these different scaling behavior ! Roy A. Lacey HIC03

21. Cent Cent PHENIX PRELIMINARY PHENIX PRELIMINARY Centrality Dependence Compatible with: Npart scaling scaling Scaling compatible with quenching and Flow Roy A. Lacey HIC03

22. “v2 pT Scaling” “High” and “low” pT charged hadrons show similar scaling Common denominator ? Roy A. Lacey HIC03

23. v2 Scaling “v2 Centrality Scaling” Molnar et al. V2 Scaling observed in models Roy A. Lacey HIC03

24. “v2 centrality Scaling” 00-05 Preliminary Two Different scaling patterns are obtained --- Respective dominance of Jets and flow-like contributions Roy A. Lacey HIC03

25. R2 pT PHENIX PRELIMINARY Reference Range Dependence v2 does not show significant dependence on pTRef Very Important --- v2(rxpln) ~ v2(corr) Roy A. Lacey HIC03

26. R2 pT Assorted Correlation Functions for p+p & Au+Au • Asymmetry of Correlation • function sensitive to: • pTRef • Charge Selection • Consistent with presence of • Jets Jets correlated with Reaction plane Roy A. Lacey HIC03

27. Observables: • high & low pT particles are correlated • v2 independent of pT reference range • scaling of v2 • away-side jet suppressed in central collisions proven proven proven proven Summary/Picture Jets are correlated with the Reaction Plane due to Quenching … then thermalized matter expands From pressure build up -> elliptic flow -> v2 Jet-quenching early Jets “remember” geometry (-> v2) Consistent picture for quenching, v2, jets Roy A. Lacey HIC03