EMCal resolution 450 ps
Inclusive identified hadron spectra use
TOF in East Arm
->K+K- uses TOF-TOF, EMCal-EMCal, and TOF-EMCal in East
->e+e- uses RICH,EMCal-EMCal in
East-West, East-East, and West-West
PHENIX Particle Identification for , K, and p /K Separation in TOF up to 2 GeV/cK/p Separation in TOF up to 4 GeV/c
p
Mixed Event Calculated
Background
Actual PairsFit to a Relativistic BW shape
convolved with a 1.20 MeV Gaussian
Note the 1 MeV mass binning
Relativistic Breit-Wigner convolved with a 1.2 MeV Gaussian
Signal Detected as K+K- Pairs in TOF-TOF Signal Detected as K+K- Pairs in TOF-EMCal3)
Measurements of the ->K+K- with
PHENIX in Au+Au Collisions at 200
GeV at RHIC
Charles F. Maguire
Vanderbilt University
(for the PHENIX collaboration)
momentum resolution p/p ~ 1% 1% p
TOF resolution 120 ps
Final results for the Line Shape and the Yields of the Final results for the Line Shape and the Yields of the as a Function of Centrality as a Function of CentralityCombination of TOF-TOF, TOF-EMCal, and EMCal-EMCal Data: Combination of TOF-TOF, TOF-EMCal, and EMCal-EMCal Data: All Mutually ConsistentAll Mutually Consistent
Mixed Event Calculated
Background
Actual Pairs
Conclusions for the Yield in Au+Au Collisions
at 200 GeV
The yield per participant saturates as a function of
centrality
The Temperature is constant as a function of
centrality
Conclusions for the Mass Centroid ofthe in Au+Au collisions at 200 GeV
Within the experimental error limits (stat , stat < 1 MeV) the centroid mass
value agrees with the PDG valueand
there is no dependence onthe centrality of the collision
Conclusions for the Mass Width ofthe in Au+Au collisions at 200 GeV
Within the experimental error limits (stat , stat < 0.5 MeV) the width value
agrees with the PDG valueand
there is no dependence onthe centrality of the collision
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 .The good pair mass resolution enables us to set narrow constraints on the line shape.
R. Rapp nucl-th/0204003
Restoration of approximate chiral symmetry may modify the mass and width in medium
Mass = 1019.456 +/- 0.020 MeVBreit-Wigner = 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 K+K- and e+e- when the decays in medium ( ~ 44 fm/c)
Compare different pair pT ranges
Final state interactions of kaons may lower the apparent measured branching fraction of K+K- relative to e+e-
Measure both channels in the same detector
Theoretical Interest of the in Collisions at RHIC
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