PHENIX photons and dileptons

Electromagnetic probes such as dileptons and photons are useful to investigate the thermodynamical state of the early stages of heavy-ion collisions. The PHENIX experiment has measured both photons and dileptons in p+p, d+Au, and Au+Au collisions. An excess of dilepton yield over the expected hadronic contribution is seen in the mass region 0.2–0.8 GeV/c2 in Au+Au collisions, most prominently at low pT and in central collisions. Direct photons are measured through their internal conversion to electron pairs. We observe a large enhancement in Au+Au collisions over the p+p yield scaled by the number of binary collisions. The latest results from d+Au collisions show that this enhancement cannot be attributed to cold-nuclear-matter effects.