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

1) 2)

4)

5)