Dielectron Mass Spectra in sqrt{s_{NN}} = 200 GeV Cu+Cu Collisions at PHENIX

Abstract

The dielectron mass spectrum consists of light vector meson decays, correlated heavy quark contributions and decays from other hadronic and photonic sources. Thermal radiation and modifications to the light vector mesons may provide additional signals at low masses above known hadronic sources. The PHENIX sqrt{sNN} = 200 GeV Au+Au and Cu+Cu analyses have measured a centrality dependent excess in the the low mass region between 0.15 GeV/c^2 and 0.75 GeV/c^2. Between the phi and the J/psi, in the intermediate mass range, the correlated heavy quark decays are the primary dielectron source; direct photons may augment this region as well. The Cu+Cu system is sensitive to the onset of the dielectron excess. By studying the Cu+Cu mass spectra and yields as a function of pair transverse momentum and collision centrality we obtain further understanding of its behavior. Comparisons to the PHENIX Au+Au and p+p measurements an extrapolations from theory are presented.