Direct photon production and interferometry in $\sqrt{s}_{NN}$=200 GeV Au+Au and in $\sqrt{s}_{NN}$=2.76 TeV Pb+Pb collisions

TL;DR

This study uses hydrodynamic modeling to analyze direct photon production and interferometry in heavy-ion collisions at RHIC and LHC energies, comparing results with experimental data and examining photon correlations.

Contribution

It demonstrates that an ideal hydrodynamic model can reproduce direct photon spectra but underestimates elliptic flow, providing insights into photon interferometry and collision centrality effects.

Findings

Hydrodynamic model reproduces photon spectra at RHIC and LHC energies.

Model underestimates elliptic flow compared to experimental data.

HBT radii show little dependence on collision centrality or energy.

Abstract

Direct photon production, in $\sqrt{s_{NN}}$=200 GeV Au+Au and in $\sqrt{s_{NN}}$=2.76 TeV Pb+Pb collisions, are studied in a hydrodynamic model. Ideal hydrodynamic model, initialised to reproduce experimentally charged particle spectra in RHIC and LHC energy, also reproduces the PHENIX and ALICE measurements for the direct photon spectra in Au+Au collisions at RHIC and Pb+Pb collisions at LHC. The model however produces less elliptic flow than in experiment. Discrepancy between experiment and hydrodynamic simulation is comparatively less in Pb+Pb collisions at LHC than in Au+Au collisions at RHIC. We also studied direct photon correlation and determined the HBT radii. In 0-10%-50-60% collisions, HBT radii in Au+Au or in Pb+Pb collisions do not show large centrality dependence. Energy dependence of the HBT radii for direct photons is also not large.