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

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

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

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

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

Roy A. Lacey HIC03 y x 200 GeV Extreme Quenching not Sufficient to Account for Observed N part Dependence of V 2 B. Muller nucl-th/ The Problem V2 from calculations which assume quenching

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

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

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

Roy A. Lacey HIC03 pT v 2 characterize the Anisotropy Extracting v2 via Fixed Correlations

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

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

Roy A. Lacey HIC03 `d+Au Min Bias Au+Au60-90% Peripheral Au+Au is essentially identical d+Au Comparison of d+Au and Au+Au

Roy A. Lacey HIC03 Comparison of d+Au and Au+Au Escaping Jet “Near Side” Suppressed Jet “Away Side” d+Au Min Bias Au+Au0-5% Apparent “away-side suppression

Roy A. Lacey HIC03d+Au Min Bias Au+Au % Mid-Central events indicate sizeable harmonic contributions Comparison of d+Au and Au+Au

Roy A. Lacey HIC03 Comparison of 130 and 200 GeV Results Anisotropy (v 2 ) essentially identical PHENIX Preliminary

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

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

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

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

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

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

Roy A. Lacey HIC03 v 2 does not show significant dependence on pT Ref Very Important --- v 2 (rxpln) ~ v 2 (corr) Reference Range Dependence pT R2R2 PHENIX PRELIMINARY

Roy A. Lacey HIC03 Assorted Correlation Functions for p+p & Au+Au Asymmetry of Correlation function sensitive to: pT Ref Charge Selection Consistent with presence of Jets pT R2R2 Jets correlated with Reaction plane

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