Speaker
Description
PHENIX has observed that a large number of direct photons are radiated during the evolution of the strongly coupled QGP produced in Au+Au collision at 200 GeV to hadron resonance matter. The direct photons are emitted with a large azimuthal anisotropy. PHENIX has extended this study using large data samples from Au+Au collisions at 39, 62.4, and 200 GeV, and Cu+Cu collisions at 200 GeV. For a given beam energy the direct photon yield scales with the number of binary collisions Ncoll for all centrality selections at all pT. At high pT the Ncoll scaled direct photon yield from p+p collisions agrees with the heavy ion data as expected. However, at low pT the yield from heavy ion collisions exceeds the yield from p+p significantly. Comparing the low pT direct photon yield across beam energies as a function of the produced charged particle density dNch/d reveals that the yield is proportional to (dNch/d)1.25. In this talk we will discuss these new results and their implications. We will also show updated results on direct photon yields and azimuthal anisotropies v2 and v3 from high statistics Au+Au data at 200 GeV.
