The measurement of photons, direct photons as well as decay photons from π0 and η decays, has been major tool for the study of the quark-gluon plasma (QGP) phase possibly created in heavy-ion collisions at RHIC.
The measurement of π0s and ηs with the PHENIX EMCal allows to study the energy-loss of hard-scattered partons in the QGP based on identified particles up to transverse momenta of pT = 20 GeV/c. The measurement of direct photons provides at high pT a baseline for hard-scattering processes in the heavy-ion collision, while at lower pT additional photon sources can indicate the creation of a QGP, e.g. thermal radiation from the QGP or photon-Bremsstrahlung of hard-scattered quarks traversing the QGP.
In this talk an overview of the direct photons measurements by the PHENIX experiment will be presented, as well as a detailed study of the energy and system-size dependence of π0 suppression in heavy-ion collisions.
