Main Image
Volume 345 - International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (HardProbes2018) - Electroweak Probes
PHENIX measurements of beam energy and centrality dependence of direct photon emission in heavy ion collisions
A. Drees
Full text: pdf
Pre-published on: 2019 January 21
Published on:
In this talk the PHENIX collaboration presents new measurements of low momentum direct photons from Cu+Cu at 200 GeV and Au+Au at 62.4 GeV and 39 GeV. A large excess of direct photons over the scaled $p$+$p$ yield is found. The comparison of the new data with data from Au+Au at 200 GeV and ALICE data from 2.76 TeV reveals that at low-$p_{T}$ the spectra of direct photons and their integrated yield above 1 GeV/c follow a universal scaling as a function of the charged-particle multiplicity, $(dN_{ch}/d\eta)^{\alpha}$, with $\alpha = 1.25$, independent of collision centrality or center of mass energy. The observed scaling properties suggests that the emission source has similar properties for all observed systems.
Open Access
Creative Commons LicenseCopyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.