EMCal resolution 450 ps

1. Measurements of the f->K+K- with PHENIX in Au+Au Collisions at 200 GeV at RHICCharles F. MaguireVanderbilt University(for the PHENIX collaboration) p/K Separation in TOF up to 2 GeV/c K/p Separation in TOF up to 4 GeV/c PHENIX Particle Identification for , K, and p Theoretical Interest of the f in Collisions at RHIC EMCal resolution 450 ps Inclusive identified hadron spectra use TOF in East Armf->K+K- uses TOF-TOF, EMCal-EMCal, and TOF-EMCal in Eastf->e+e- uses RICH,EMCal-EMCal inEast-West, East-East, and West-West • Restoration of approximate chiral symmetry may modify the f mass and width in medium • Mass = 1019.456 +/- 0.020 MeVBreit-Wigner G = 4.26 +/- 0.06 MeV • Look for variations with centrality • Compare to p+p and d+A results • These modifications may result in a change in the branching fraction of fK+K- and fe+e- when the f decays in medium (tf~ 44 fm/c) • Compare different pair pT ranges • Final state interactions of kaons may lower the apparent measured branching fraction of fK+K- relative to fe+e- • Measure both channels in the same detector R. Rapp nucl-th/0204003 Actual Pairs Fit to a Relativistic BW shapeconvolved with a 1.20 MeV Gaussian Note the 1 MeV mass binning Mixed Event Calculated Background Conclusions for the Mass Centroid of the f in Au+Au collisions at 200 GeV Within the experimental error limits(sstat , sstat < 1 MeV) the f centroid mass value agrees with the PDG valueandthere is no dependence onthe centrality of the collision Conclusions for the Mass Width of the f in Au+Au collisions at 200 GeV Within the experimental error limits(sstat , sstat < 0.5 MeV) the f width value agrees with the PDG valueandthere is no dependence onthe centrality of the collision Conclusions for the f Yield in Au+Au Collisionsat 200 GeV The yield per participant saturates as a function of centralityThe Temperature is constant as a function of centrality 1) 2) momentum resolution p/p ~ 1%  1% p p K TOF resolution 120 ps p 3) fSignal Detected as K+K- Pairs in TOF-TOF fSignal Detectedas K+K- Pairs in TOF-EMCal Actual Pairs Relativistic Breit-Wigner convolved with a 1.2 MeV Gaussian Mixed Event Calculated Background Final results for the Line Shape and the Yields of the f as a Function of Centrality Combination of TOF-TOF, TOF-EMCal, and EMCal-EMCal Data: All Mutually Consistent The excellent single particle momentum resolution of the PHENIX spectrometer leads to a pair mass resolution of ~1.2 MeV, much less than the intrinsic width of the f .The good pair mass resolution enables us to set narrow constraints on the line shape. 4) 5)