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P. Chung Nuclear Chemistry, SUNY, Stony Brook

Evidence for a long-range pion emission source in Au+Au Collisions at. P. Chung Nuclear Chemistry, SUNY, Stony Brook. Outline Motivation Brief Review of Correlation analysis methods Data Analysis & Results Correlation functions Source functions

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P. Chung Nuclear Chemistry, SUNY, Stony Brook

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  1. Evidence for a long-range pion emission source in Au+Au Collisions at P. Chung Nuclear Chemistry, SUNY, Stony Brook

  2. Outline • Motivation • Brief Review of Correlation analysis methods • Data Analysis & Results • Correlation functions • Source functions • Source parameters & dependence (centrality, mT, etc) • Conclusion/s

  3. hadronic phase and freeze-out QGP and hydrodynamic expansion initial state pre-equilibrium hadronization Motivation Conjecture of collisions at RHIC : Courtesy S. Bass Which observables & phenomena connect to the de-confined stage?

  4. Motivation One Scenario: Increased System Entropy that survives hadronization QGP and hydrodynamic expansion Expectation: A de-confined phase leads to an emitting system characterized by a much larger space-time extent thanwould be expected from a system which remained in the hadronic phase

  5. Experimental Setup PHENIX Detector Several Subsystems exploited for the analysis Excellent Pid is achieved

  6. Cuts Dphi (rad) Dz (cm)

  7. Cuts Dphi (rad) Dz (cm)

  8. Analysis Summary • Image analysis in PHENIX Follows three basic steps. • Track selection • Evaluation of the • Correlation Functions (with pair-cuts etc.) • Imaging of • Correlation functions • Fits to correlation function Dphi >0.02 dz < 5 cm Dphi >0.01 dz > 5 cm

  9. Analysis Technique Correlation Function Direct Fits to the Correlation Functions Imaging Source Function

  10. Emitting source Imaging Technique Technique Devised by: D. Brown, P. Danielewicz, PLB 398:252 (1997).PRC 57:2474 (1998). Inversion of Linear integral equation to obtain source function 1D Koonin Pratt Encodes FSI Source function (Distribution of pair separations) Correlation function Inversion of this integral equation == Source Function

  11. Imaging Inversion procedure

  12. PHENIX Preliminary Results • Non Gaussian tail observed in source function

  13. PHENIX Preliminary Results • Non Gaussian tail observed in source function

  14. E895 PHENIX Preliminary E895 Results • Non Gaussian tail NOT observed at the AGS

  15. Correlation Fits [Parameterized form for S(r)] + convolution with kernel  calculated C(q) Measured correlation function Minimize Chi-squared Parameters of the source function

  16. Extraction of Source Parameters Fit Function (Pratt et al.) Radii Pair Fractions Bessel Functions This fit function allows extraction of both the short- and long-range components of the source image

  17. Quick Test - 1 Input source function recovered Procedure is Robust !

  18. Fitting correlation functions Kinematics “Spheroid/Blimp” Ansatz Brown & Danielewicz PRC 64, 014902 (2001) “spheroid/Blimp” parameters

  19. Sensitivity Tests Fix RT = R and vary a Source parameters Recovered

  20. Sensitivity Tests Fix a and vary R Source parameters Recovered

  21. PHENIX Preliminary Results • Spheroid source function yield excellent fits to data

  22. Comparison of Source Functions Same source functions from different parameterization

  23. Short and long-range components of the source T. Csorgo M. Csanad Short-range  Long-range 

  24. Short and long-range components of the source T. Csorgo M. Csanad

  25. Short and long-range components of the source Core Halo assumption T. Csorgo M. Csanad Expt 

  26. Next Steps; 3D imaging/moment fitting Higher l moments  angular deformation of source

  27. Next Steps; 3D imaging/moment fitting Simulation results Solid proof of principle

  28. Summary • First Extensive study of two-pion 1D source • images in Au+Au collisions at RHIC • Results indicate evidence for non-Gaussian tail • Long-range behavior of source function ~ 3x short-range • Centrality dependence of radius parameters and lambda • Fraction in compatible with simple estimate of omega decay Further detailed 3D analysis in progress to pin-down origin of long-range behavior

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