Direct photons at RHIC — Preliminary results and prospects

Abstract

Penetrating probes like direct photons were always considered a crucial tool to study the initial conditions established in relativistic heavy ion collisions and to possibly map out the entire time history of the collision. Technically, however, the direct photon measurement is very challenging, primarily due to the large photon background from hadron decays. Now that after the first three years of RHIC operations the hadron spectra are well established there is an increased interest in the community to extract the spectrum of direct (non-hadronic) photons both from p+p, d+Au and Au+Au data. This paper reports on the currently available results and assesses what new results might be expected in the near future.