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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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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 • Source parameters & dependence (centrality, mT, etc) • Conclusion/s
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?
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
Experimental Setup PHENIX Detector Several Subsystems exploited for the analysis Excellent Pid is achieved
Cuts Dphi (rad) Dz (cm)
Cuts Dphi (rad) Dz (cm)
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
Analysis Technique Correlation Function Direct Fits to the Correlation Functions Imaging Source Function
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
Imaging Inversion procedure
PHENIX Preliminary Results • Non Gaussian tail observed in source function
PHENIX Preliminary Results • Non Gaussian tail observed in source function
E895 PHENIX Preliminary E895 Results • Non Gaussian tail NOT observed at the AGS
Correlation Fits [Parameterized form for S(r)] + convolution with kernel calculated C(q) Measured correlation function Minimize Chi-squared Parameters of the source function
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
Quick Test - 1 Input source function recovered Procedure is Robust !
Fitting correlation functions Kinematics “Spheroid/Blimp” Ansatz Brown & Danielewicz PRC 64, 014902 (2001) “spheroid/Blimp” parameters
Sensitivity Tests Fix RT = R and vary a Source parameters Recovered
Sensitivity Tests Fix a and vary R Source parameters Recovered
PHENIX Preliminary Results • Spheroid source function yield excellent fits to data
Comparison of Source Functions Same source functions from different parameterization
Short and long-range components of the source T. Csorgo M. Csanad Short-range Long-range
Short and long-range components of the source T. Csorgo M. Csanad
Short and long-range components of the source Core Halo assumption T. Csorgo M. Csanad Expt
Next Steps; 3D imaging/moment fitting Higher l moments angular deformation of source
Next Steps; 3D imaging/moment fitting Simulation results Solid proof of principle
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