Measurements of dilepton continuum at the PHENIX experiment at RHIC

TL;DR

The PHENIX experiment measured dielectron production in heavy-ion and proton collisions at RHIC, finding an excess in Au+Au collisions indicating possible medium effects, and consistent charm production between phi and J/psi masses.

Contribution

First measurement of dielectron continuum in Au+Au and p+p collisions at RHIC, revealing medium-induced enhancements and insights into charm production mechanisms.

Findings

Dielectron yield in Au+Au is significantly enhanced over model expectations.

Yield increases faster than participant nucleons with collision centrality.

Continuum yield between phi and J/psi matches correlated charm production predictions.

Abstract

PHENIX has measured the dielectron continuum in sqrt(s_(NN))=200 GeV Au+Au and p+p collisions. In minimum bias Au+Au collisions the dielectron yield in the mass range between 150 and 750 MeV/c^2 is enhanced by a factor of 3.4 +/- 0.2(stat.) +/- 1.3(syst.) +/- 0.7(model) compared to the expectation from our model of hadron decays that well reproduces the mass spectrum in p+p collisions. The integrated yield increases faster with the centrality of the collisions than the number of participating nucleons, suggesting emission from scattering processes in the dense medium. The continuum yield between the masses of the phi and the J/psi meson is consistent with expectations from correlated ccbar production, though other mechanisms are not ruled out.