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Three-Particle Correlation Measurements at RHIC

Three-Particle Correlation Measurements at RHIC. Jason Glyndwr Ulery Purdue University 8 August 2007 XXXVII International Symposium on MultiParticle Dynamics. Outline. Motivation Three 3-Particle Analyses at RHIC PHENIX Analysis STAR Cumulant Analysis STAR 2-Component Analysis

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Three-Particle Correlation Measurements at RHIC

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  1. Three-Particle Correlation Measurements at RHIC Jason Glyndwr Ulery Purdue University 8 August 2007 XXXVII International Symposium on MultiParticle Dynamics

  2. Outline • Motivation • Three 3-Particle Analyses at RHIC • PHENIX Analysis • STAR Cumulant Analysis • STAR 2-Component Analysis • Summary and Conclusions ISMD Jason Glyndwr Ulery

  3. RHIC Discovery STAR PRL 90 (2003) 082302 STARPRL 91 (2003) 072304 pTAssoc>2 GeV/c • Perfect Liquid: v2, jet-quenching • Jets make a good probe of the medium • Can be calculated in pQCD so calibrated. • Expected to be modified by the medium. • Two-particle correlations at RHIC show medium modification. Inclusive pTAssoc STAR PRL 95 (2005) 152301 Ulery (STAR) DNP 2004 STAR PRL 95 (2005) 152301 ISMD Jason Glyndwr Ulery

  4. Motivation near near Medium Medium away away Deflected Jets Conical Emission PHENIX PRL 97, 052301 (2006) Horner (STAR) QM2006 2.5<pTTrigger<4 GeV/c 1<pTAssoc<2.5 GeV/c 3<pTTrigger<4 GeV/c 1<pTAssoc<2.5 GeV/c 0-12% Au+Au 0-5% PHENIX • Broadened and maybe double humped structure on the away-side in 2-particle correlations. • Could be caused by: • Large angle gluon radiation (Vitev and Polsa and Salgado). • Deflected jets, due to flow (Armesto, Salgado and Wiedemann) and/or path length dependent energy loss (Chiu and Hwa). • Hydrodynamic conical flow from mach cone shock-waves (Stoecker, Casalderrey-Solanda, Shuryak and Teaney, Renk, Ruppert and Muller). • Cerenkov gluon radiation (Dremin, Koch). • Three-particle correlations to distinguish them. ISMD Jason Glyndwr Ulery

  5. Three 3-Particle Analyses at RHIC Δ1 STAR 2-Component PHENIX Analysis STAR Cumulant Performed in - space =-Trigger Performed in polar coord. space defined by trigger Performed in - space =Trigger- Mathematically defined 2-component approach 2-component approach Systematics due to flow normalization Systematics due to flow normalization Difficult interpretation of results PHENIX Preliminary Δ2 Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 Ajitanand (PHENIX) HP06, IWCF’06 Pruneau (STAR) QM’06 ISMD Jason Glyndwr Ulery

  6. PHENIX Raw Signals Same Side Near-Side Away Side * * *= Au+Au • Uses a polar coordinate system based on the trigger particle direction. • Natural coordinate system if away-side axis is know. • 2.5<pTTrig<4 GeV/c • 1<pTAssoc<2.5 GeV/c 40-60 % 10-20 % 0-5 % Ajitanand (PHENIX) HP06, IWCF’06 ISMD Jason Glyndwr Ulery

  7. PHENIX Simulations Ajitanand (PHENIX) HP06, IWCF’06 Simulated Mach Cone *=0 • Simulations with PHENIX acceptance. • With perfect acceptance expect: • Peak at *=0 for deflected jet • No * dependence for conical emission. Simulated Deflected jet ISMD Jason Glyndwr Ulery

  8. PHENIX Results * Projections v2 subtracted 2-particle dominated 2-particle dominated v2 and 2-particle subtracted Deflected Mach-cone PHENIX PRL 97, 052301 (2006) Ajitanand (PHENIX) HP06, IWCF’06 • 3-particle/2-particle ~ 1/3, very large • Residual background? v2 subtracted Au+Au 10-20% • Shape consistent with simulated mach-cone. ISMD Jason Glyndwr Ulery

  9. STAR Cumulant Pruneau (STAR) QM’06 • Done in - space where =Trigger-Associated • Trigger particles of 3<pT<4 GeV/c. • Associated particles of 1<pT<2 GeV/c. • Mathematically Defined. • Measures all three-particle correlations. C3(12,13) = 3(12,13) - 2(12)1(3) – 2(13)1(2) - 2(12- 13)1(1) - 2 1(1)1(2)1(3) ISMD Jason Glyndwr Ulery

  10. STAR Cumulant Results Au+Au 50-80% Au+Au 10-30% Au+Au 0-10% • Non-zero 3-particle correlation. • Results contain all possible 3-particle correlations; jet, flow and jet  flow. • Further interpretation requires model assumptions. • Non-Poisson fluctuations can leave residual 2-particle correlations. Pruneau (STAR) QM’06 ISMD Jason Glyndwr Ulery

  11. STAR 2-Component Δ1 Trigger • Trigger particle 3<pT<4 GeV/c with pairs of associated particle 1<pT<2 GeV/c.. • - space • Event=particles jet-like correlated with trigger + background particles • Raw signal contains (Jet+Bkgd)  (Jet+Bkgd). • To obtain JetJet we must subtract BkgdBkgd and JetBkgd (and BkgdJet.) Δ2 Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 ISMD Jason Glyndwr Ulery

  12. JetBackground (Hard-Soft)One particle is jet-like correlated the other is from background. Hard-Soft Jet-like correlated • JetBackground term • 2-particle jet-like signal (mini panel) folded with normalized 2-particle background. Δ2 Raw Background ZYA1 Δ1 Δ Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 ISMD Jason Glyndwr Ulery

  13. BackgroundBackground (Soft-Soft)Both associated particles are from background. • Trigger particle from one event mixed with pairs of background particles from an another event of the same centrality. • Contains all correlations independent of the trigger. • Flow, minijets, other jets… Δ2 Δ1 Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 ISMD Jason Glyndwr Ulery

  14. BackgroundBackground (Flow) Δ2 Δ1 Δ2 Δ1 v2Triggerv2Associated • Flow correlations between trigger and associated particles. • v2 is taken as average of reaction plane and 4-particle measurements. • Systematics uncertainty from the 2 measurements. v4 = 1.15 v22 Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 v4Triggerv4Associated + v2v2v4 ISMD Jason Glyndwr Ulery

  15. Conical Flow vs Deflected Jets near near near Medium Medium Medium away away away di-jets Renk, Ruppert hep-ph /0702102 deflected jets Conical Emission ISMD Jason Glyndwr Ulery

  16. STAR 2-Component Results Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 Au+Au Central 0-12% Triggered pp d+Au Away Au+Au 50-80% Au+Au 30-50% Near Au+Au 10-30% Au+Au 0-10% ISMD Jason Glyndwr Ulery

  17. Yields Open symbols, 0-12% ZDC are shifted Off-diagonal 1.45 rad. On-diagonal 1.45 rad. • Yields show significant off-diagonal signal in central Au+Au collisions. Away Average Signal in 0.7x0.7 Squares ISMD Jason Glyndwr Ulery

  18. Projections d+Au Au+Au 10-30% Au+Au 0-12% • On-diagonal and off-diagonal projections. • Yellow bands are systematic errors. • Significant off-diagonal peaks. (1+2)/2 (1-2)/2 Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 ISMD Jason Glyndwr Ulery

  19. Angle and Yields Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 • Gaussians fit to off-diagonal projections extract conical emission angle. • No apparent centrality dependence on angle. ZDC (1-2)/2 ISMD Jason Glyndwr Ulery

  20. Associated PT DependenceConical Emission: Mach-cone or Cerenkov Gluons Au+Au 0-12% 3<pTTrig<4 GeV/c 0.5<pTAssoc<0.75 GeV/c 0.75<pTAssoc<1.0 GeV/c 1.0<pTAssoc<1.5 GeV/c 1.5<pTAssoc<2.0 GeV/c • Mach-cone: • angle independent associated pT • Cerenkov gluon radiation: • decreasing angle with associated pT. • Angle is consistent with increasing or no dependence on associated particle pT. Ulery (STAR), QM’05, HP’06, QM’06 Poster, IWCF’06 ISMD Jason Glyndwr Ulery

  21. Summary and Conclusions • Three 3-particle analyses at RHIC. • PHENIX Analysis • Shape consistent with conical emission simulation. • STAR Cumulant Analysis • Non-zero 3-particle correlations. • STAR 2-Component Analysis • Consistent with conical emission at about 1.45 radians in central Au+Au. • PT independent angle suggests Mach-cone emission. ISMD Jason Glyndwr Ulery

  22. ISMD Jason Glyndwr Ulery

  23. STAR 2-Component Systematics • Major sources of systematic error are from the elliptic flow measurement and the normalization. • Off-diagonal signal robust with respect to variations in v2 and normalization. • Other sources include: • effect on the trigger particle flow from requiring a correlated particle (±20% on trigger particle v2) • uncertainty in the v4 parameterization • multiplicity bias effects on the soft-soft background Reaction Plane v2 4-Particle v2 Wide Normalization Ulery IWCF’06 ISMD Jason Glyndwr Ulery

  24. Extreme Systematics • No jet flow systematic has the jet not flowing with the medium. • No v2Triggerv2Associated has no subtraction of the v2 terms. • Signal persists even in these extreme cases. No Jet Flow No v2Triggerv2Associated (1-2)/2 Ulery IWCF’06 ISMD Jason Glyndwr Ulery

  25. Widths ISMD Jason Glyndwr Ulery

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