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Surface Effects on Jet Production (2+1 correlation study)

Surface Effects on Jet Production (2+1 correlation study). Olga Barannikova for the STAR Collaboration. Outline. Motivation Evolution of jet-type correlation analyses Theoretical interpretation of data Data Analysis Results Energy loss in di-jet events Summary. M. v Leeuwen,

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Surface Effects on Jet Production (2+1 correlation study)

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  1. Surface Effects on Jet Production(2+1 correlation study) Olga Barannikova for the STAR Collaboration

  2. Outline • Motivation • Evolution of jet-type correlation analyses • Theoretical interpretation of data • Data Analysis • Results • Energy loss in di-jet events • Summary Olga Barannikova University of Illinois at Chicago

  3. M. v Leeuwen, Hangzhou ‘06 3<pTtrig<4 GeV/c 1.3<pTassoc<1.8 • One high-pT, one low-pT trigger • Reappearance of the away-side jet • Double-hump structure hints at additional physics phenomena Motivation 4<pTtrig<6 GeV/c 2<pTassoc<pTtrig PRL 91 (2003) 072304 • Signature two-particle correlation result: • Disappearance of the away side jet in central Au+Au collisions • Evidence for strongly interacting medium • Effect vanishes in peripheral/d+Au collisions Olga Barannikova University of Illinois at Chicago

  4. Energy Loss Mechanisms • Jet Quenching • Dissipation jet energy when propagating through the medium • Mach-Cone • Could result in double-hump structure on away-side • Mono-jet • Single jet on near-side • Excess on away side due to momentum conservation “away-side” “near-side” Courtesy of R .Hollis Olga Barannikova University of Illinois at Chicago

  5. Energy Loss in QCD Medium 4<pTtrig<6 GeV/c 2<pTassoc<pTtrig • To address the mechanisms of energy loss in the hot QCD medium • Mach cone (Stoecker, Casalderrey-Solana, Shuryak, Teaney) • Cherenkov gluon radiation (Koch, Majumder, Wang) • Jet quenching & fragmentation (Vitev) • Parton multiple scattering (Chiu, Hwa) • Color wake (Ruppert, Muller) • Flow-induced deflection (Armesto, Salgado, Wiedemann) • Use di-jets to explore how these effects happen PRL 91 (2003) 072304 Phys.Lett. B639 (2006) 38 Olga Barannikova University of Illinois at Chicago

  6. First Di-Jet Observation • Two high-pT triggers • Reappearance of the away-side jet • For central Au+Au collisions • First observation of di-jets • New analysis exploits this observation 8<pT(trig)<15 GeV/c PRL 97 (2006) 162301 Olga Barannikova University of Illinois at Chicago

  7. Data Analysis - Technique • Aim of this analysis is to “pin” the jet axis • Assuming di-jets • Only select events with high-pT particles back-to-back in f • Correlate all particles with this axis associates primary trigger (T1) “jet-axis” trigger (T2) associates Courtesy of R .Hollis Signal sit atop of a largely uncorrelated background Olga Barannikova University of Illinois at Chicago

  8. Unmodified Jet* Simulation Dh Modified Jet* Df Dh Simulation Df Monte-Carlo Shape Examples • Simulation of one scenario, mach-cone • New method should be sensitive to this and other effects *by M. Andrews (UIC) Olga Barannikova University of Illinois at Chicago

  9. Data Analysis – Di-Jet Selection • Correlation primary trigger (T1) and “jet-axis trigger” (T2) • Require that the 2 highest pT particles are back-to-back in f • Assume this defines the jet-axis, look in 2D-space about the second trigger Raw, uncorrected signal T1T2 T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Olga Barannikova University of Illinois at Chicago

  10. Mixed Events Background: • Accounts for: • pair acceptance • triangular shape in Dh • uncorrelated background • particles not related to initial jet Olga Barannikova University of Illinois at Chicago

  11. 0 - 10% 10-20% 20-30% 30-40% V2Removal: • Need to account for elliptic flow Phys.Rev. C72 (2005) 014904 • Dynamic weighting in analysis Note: this is the correction function for T1A1 Olga Barannikova University of Illinois at Chicago

  12. T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Normalization: T1T2 Olga Barannikova University of Illinois at Chicago

  13. T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Normalization: T2A1 Olga Barannikova University of Illinois at Chicago

  14. 0 - 10% 10-20% 20-30% 30-40% T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c 2+1 Signal Construction: Flow Background Raw Correlation Dh Dh Df Df Signal STAR Preliminary Olga Barannikova University of Illinois at Chicago

  15. Di-jet trigger Single trigger T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Preliminary Results: • Di-jet trigger • no modification on away-side • Surface dominated? • No energy loss for di-jets? • One high-pT trigger (only) • away-side modification • Mono-jets? • Energy loss for away-side jet? T1A1 T2A1_T1 STAR Preliminary Olga Barannikova University of Illinois at Chicago

  16. T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Correlated Background: T1T2 Signal + Background Background Signal • Accounting for correlated background on T1 and T2 side + - 2+1 correlation for all qualified T1, T2 pairs +,+- Correlated background (approximated by di-hadron T1A1, T2A1 correlations) + - Corrected 2+1 signal STAR Preliminary Olga Barannikova University of Illinois at Chicago

  17. T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Di-Jets in Au+Au Collisions • Correlation of associates with: • T1 (also requires a T2) • T2 • Detailed shape of near- and away-side is the same T1A1_T2 T2A1_T1 STAR Preliminary Same-side widths: Olga Barannikova University of Illinois at Chicago

  18. T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Shape Modifications Df projection • No apparent h-“ridge” • No shape modification STAR Preliminary STAR Preliminary Dh projection STAR Preliminary J. Putschke, QM2006 Olga Barannikova University of Illinois at Chicago

  19. d+Au STAR Preliminary ** T1: pT>5GeV/c T2: pT>4GeV/c A: pT>1.5GeV/c Surface Effects • If the triggers have tangential bias: expect a term related to the surface • Surface ~ R2 ~ Npart2/3 • Number of triggersper event (per number of binary collisions) • Single triggers and (all qualified) pairs behave similar to inclusives STAR Preliminary ** ** Shown are statistical errors only Olga Barannikova University of Illinois at Chicago

  20. Summary: • New analysis of 2+1 correlations • Events triggered with 2 high-pT particles • Preliminary results show a di-jet structure with this technique, with no modification • Surface bias in di-jet emission is likely, new technique allows further exploration Many thanks to A. Iordanova, R. Hollis, M. Andrews Olga Barannikova University of Illinois at Chicago

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