Thermal Photon Measurements at PHENIX

Photons provide snapshots of the evolution of relativistic heavy-ion collisions as they are emitted at all stages and do not interact with the medium strongly. With access to the versatility of RHIC, measurements of low momentum direct photons are made possible across different system sizes and beam energies. An excess of direct photons, above prompt photon production from hard scattering processes, is observed for a system size corresponding to \(\frac{dN_{ch}}{d\eta }\) of 20–30, with a large azimuthal anisotropy and a characteristic dependence on collision centrality. After subtracting the prompt photon component, the inverse slope of the spectrum is continuously increasing with the effective temperature for the \(p_{T}\) range from 1–2 GeV/c being 250 MeV/c, and about 400 MeV/c for the range from 2 to 4 GeV/c. Within the experimental uncertainty, there is no indication of a system size dependence of the inverse slope. In this proceeding, results from small system and Au+Au collisions from the PHENIX experiment will be presented.