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Stefan Kniege Johann Wolfgang Goethe Universität Frankfurt a.M.

Two- and three particle azimuthal correlations @ SPS energy. Stefan Kniege Johann Wolfgang Goethe Universität Frankfurt a.M. For the CERES collaboration. ISMD 04-09.08.2007 Berkeley, USA. Outline. High-pt correlation measurements @ SPS. Motivation for the measurement

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Stefan Kniege Johann Wolfgang Goethe Universität Frankfurt a.M.

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  1. Two- and three particle azimuthal correlations @ SPS energy Stefan Kniege Johann Wolfgang Goethe Universität Frankfurt a.M. For the CERES collaboration ISMD 04-09.08.2007 Berkeley, USA

  2. Outline High-pt correlation measurements @ SPS Motivation for the measurement Previous correlation measurements at RHIC and SPS High-pt hadron correlations at CERES (preliminary) •  CERES detector setup •  analysis method and results for • two particle correlations •  model studies to estimate systematic errors • analysis method and results for • three particle correlations Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  3. High- pt hadron correlations near side parton 1 trigger 1 associate 1 away side 2 associate 2 parton 2 Study of the fragmentation pattern of jets produced in hard parton-parton scatterings in heavy ion collisions Possibilities for measuring jet properties: • Full reconstruction of a jet • drawback: large background in A+A collisions • Measuring transverse angular • correlations with respect to a trigger •  distributions : same event /mixed events Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  4. Motivation / earlier measurements central peripheral PHENIX: nucl-ex/ 0612019 Vanishing of the away- side in case of high trigger/associate pt Non Gaussian structure on the away side nucl-ex/ 0510060 • centrality and • pt dependence of the yield/shape on the away side Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  5. Motivation / earlier measurements 21 – 26 % 9 – 13 % Centrality and energy dependence RHIC RHIC SPS PHENIX nucl-ex/0611019 non Gaussian shape also visible at SPS energies CERES: CERES Collaboration, G. Agakichev, et al. Phys. Rev. Lett. 92 (2004) 032301 Centrality depencence of shape of the away side ( !non triggered correlations of pions with pt > 1.2 GeV/c ) Key features also observable at SPS energies !? Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  6. CERES Detector setup and data sets CERES Detector Components • SDD: • Silicon Drift Detector • RICH: • Ring Imaging Cherenkov • Counters • TPC : • Time Projection Chamber • Acceptance  : (8-15)° •  : (0-360)° Data set: • 3·107Pb-Au events Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  7. near side parton 1 trigger 1 associate 1 away side 2 associate 2 parton 2 2-particle correlations Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  8. Measurement: 2 particle correlations trigger parton 1 1 associate 1 pt : (2.5-4.0) GeV/c (1.0-2.5) GeV/c 2 associate 2 parton 2 all like sign unlike sign Construction of the correlation function Investigation of different charge combinations Measured at different centralities: s/sgeom :(0-5)%, (5-10)%,(10-20)% determined by track multiplicity Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  9. Measurement: 2 particle correlations Assumption: two contributions in the correlation funcion: flow-like let-like : elliptic flow in trigger- (A) and associate (B) pt range determined with CERES reaction-plane analysis Removing flow contribution ZYAM (Zero Yield At Minimum) J(min) = 0 :  Subtract flow from C() to get Jet correlations Conditional yield Jet- associated particles per trigger Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  10. Results: Conditional yield all charge combinations pt: trigger :(2.5-4.0) GeV/c ; associates : (1.0-2.5) GeV/c flow contribution (stat. unceratinties in v2) Conditional yield Correlation function Non gaussian shape on the away side for more central collisions Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  11. Results: charge selection Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c all like sign unlike sign • For all centralities: • Yield on the near side more pronounced for unlike sign particles •  charge correlation in the fragmentation process • Yield on the away side is higher for like sign particles • initial collisions Raw Correlation flow contribution s/sgeom = 0 - 5 % s/sgeom = 5 - 10 % s/sgeom = 10 - 20 % Conditional yield Charge dependence: properties of initial state and fragmentation process Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  12. + - trigger charge trigger charge Detailed view on charge combinations Trigger sample dominated by positive triggers triggers sample dominated by positive triggers Away side yield higher for positive associates  Initial state dominated by positives +/+ +/- -/+ -/- s/sgeom = 0 - 5 % • Trigger and associates (initial state) • dominted by positive paritles • Near side yield higher for • unlike sign particles Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  13. Summary of results on two particle correlations • Trigger and away side yield dominated by positive particles •  Initial state dominated by positive particles • Near side: Higher yield for unlike than for like sign pairs •  charge correlations in fragmentaion process • Away side: Non gaussian shape for central collisions •  Final state interactions with the medium Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  14. Interlude : Systematic studies Current analysis (ZYAM): flow + jet Toy model : Two uncorrelated sources: jet-trigger random to reaction plane • Jet-trigger events: • trigger + jet associates • trigger + flow associates •  random component Flow-trigger events: trigger andassociates flowing Input: v2trig = 0.03 ; v2asso = 0.02; yield/trigger number of flow associates <nflow> 15probability for a jet trigger :pjet =0.1 nflow >> ytrig random component ~ pjet Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  15. Signal components Input and extracted yield ZYAM Interlude : Systematic errors Generate correlation function and apply ZYAM to extract yield: Signal components Input and extracted yield ZYAM jet events flow events Random component leads to overestimated flow modulatoion in ZYAM ( small v2 not visible) Extracted yield in good agreement to input Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  16. Interlude : Systematic errors Increase of v2 : v2trig = 0.1 ; v2asso = 0.07 corresponding to s/sgeom = 10 - 20 % Signal components Input and extracted yield ZYAM jet events flow events Same relative overestimation of v2 has large impact due to subtraction Significant difference of the extracted yield  Shape and yield Relative change in v2 : pjet*v2  Can pjetthis quantity bedetermined? Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  17. Determining jet trigger probability pjet Comparison of number of jetassociates to pairs of associates : <n jet-asso.> / trig.(jet) : <n jet-asso. pairs> / trig.(jet) ( poissonian distribution of associates ) Jet associate particles: particle yield/trigger pair yield(projection)/trigger Pairs of jet associates: unknown known from two/three particle analysis Possibility to determine yield per jet ? Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  18. 3-particle correlations Investigating the structure on the away side Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  19. 3 particle correlations Impact of jet topologies on the 2 particle correlation function Non gaussian shape on the away side Event by event deflection of jets Cone like structure in one event Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c s/sgeom :(0-5)% pt : (2.5-4.0) GeV/c (1.0-2.5) GeV/c Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  20. Toy Model : Cone vs. Event by Event Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  21. Contribution to 3-particle correlations flow measured ! Two particle correlation: Three particle correlations: (J. G. Ulery and F. Wang, nucl-ex/0609016) 1. jet-jet 2. hard*soft 3. soft soft (mixed events) +flowing trigger + Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  22. Three particle correlation functions s/sgeom: (0.0-5.0)% Dfti Dftj Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c all charge combinations C3 C3 unlike sign assoc. like sign assoc. C3 Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA Preliminary

  23. Background contributions Backgr.: hard*soft soft*soft trigger flowing yield correlations function yield ZYAM a.u. - (..+..+.. ) = offdiogonal components preliminary preliminary Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  24. Charge dependence of Yield Different charge combinations of associate particles Correlation function charge correlations all unlike sign like sign a.u. a.u. a.u. Yield preliminary preliminary preliminary Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  25. Summary • Non gaussian shape on the away side of • 2 particle correlation function • Shape of the correlation function for different charge • combinations indicate • charge ordering in the fragmentation process • Shape of the 3 particle correlations indicate cone like structure • on the away side of the jet Further investigations are needed to draw final conclusions Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  26. Thank you for your attention The CERES collaboration D. Adamova, G. Agakichiev, D. Antończyk, A. Andronic, H. Appelshäuser, V. Belaga, J. Bielcikova, P. Braun-Munzinger, O. Busch, A. Castillo, A. Cherlin, S. Damjanovic, T. Dietel, L. Dietrich, A. Drees, S. Esumi, K. Filimonov, K. Fomenko, Z. Fraenkel, C. Garabatos, P. Glässel, G. Hering, J. Holeczek, S. Kniege, V. Kushpil, B. Lenkeit, W. Ludolphs, A. Maas, A. Marin, J. Milosevic, A. Milov, D. Miśkowiec, R. Ortega, Yu. Panebrattsev, O. Petchenova, V. Petracek, A. Pfeiffer, M.Płoskoń, S. Radomski, J. Rak, Ravinovich, P. Rehak, W. Schmitz, J. Schukraft, H. Sako, S. Shimansky, S. Sedykh, J. Stachel, M. Sumbera, H. Tilsner, I. Tserruya, G. Tsiledakis, T. Wienold, B. Windelband, J.P. Wessels, J.P. Wurm, W. Xie, S. Yurevich, V. Yurevich NPI ASCR, Rez, Czech Republic GSI Darmstadt, Germany Frankfurt University, Germany Heidelberg University, Germany JINR Dubna, Russia Weizmann Institute, Rehovot, Israel SUNY at Stony Brook, USA CERN, Switzerland BNL, Upton, USA Münster University, Germany MPI Heidelberg, Germany Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  27. Backup Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  28. Alternative: correlations among the associates pt : (1.0-2.5) GeV/c Dfij 0° 180° trigger S: trigger and accociates from the same event B: trigger, accociate1, associate2 from different events cut on associate Df with respect to trigger trigger Orientation of angles with respect to the trigger steeply falling Df distribution Df trig<->ass> 1.0 a.u. Df (rad) Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  29. Monto Carlo studies of the background a.u. s/sgeom: (0.0-5.0)% • Monte Carlo construction of non jet-jet • contributions to the measured data • based on the 2 particle conditional yield • and measured elliptic flow. C(Df) data flow*jet + flow*flow No trigger separation cut Preliminary flow*flow Yield of away side pairs normalized by steeply falling Dfdistribution C(Df) flow comp. subtracted Preliminary Preliminary Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c Indication of cone structure on the away side  needs further investigation Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  30. Yield of away side pairs a.u. trigger sep. cutDfTA>1.0 Sructure on the away side also seen with cut around the trigger region T Preliminary Indication of cone structure on the away side  needs further investigation Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  31. Three partile correlations corr hard soft soft soft trigger flow yield all unlike sign associates like sign associates Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  32. Misc. Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  33. Determining jet trigger probability pjet : mean number of associates (pairs) per trigger (jet) Comparison of number of jetassociates to pairs of associates Poissonian distribution of associates Jet associate particles: particle yield/trigger pair yield(projection)/trigger Pairs of jet associates: unknown known from two/three particle analysis Possibilily to determine yield per jet ? Possibilily to determine yield per jet ? Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  34. Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  35. Jet- Jet yield raw correlations (all charge combinations) Subtraction of two particle correlations ( soft*soft , hard*soft ) (J. G. Ulery and F. Wang nucl-ex/0609016) Preliminary Yield (Preliminary) s/sgeom: (0.0-5.0)% Trigger pt : (2.5-4.0) GeV/c Associate pt : (1.0-2.5) GeV/c Off-diagonal components remain Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

  36. Background contributions Backgr.: trigger flowing soft*soft hard*soft yield correlations function - (..+..+.. ) = clear offdiogonal components Stefan Kniege ISMD 04-09.08.2007, Berkeley, USA

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