On the Role of Prompt Photons in the Anisotropic Emission of Direct Photons -- Direct Photons from Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV with IP-Glasma Initial Condition

TL;DR

This study models the anisotropic emission of direct photons in Au+Au collisions at RHIC energies, achieving good agreement with data for spectra and flow coefficients by incorporating prompt photon contributions.

Contribution

It demonstrates the importance of prompt photon contributions in accurately modeling direct photon flow and spectra in heavy-ion collisions.

Findings

Good agreement with experimental spectra across centralities.

Flow coefficients match data when prompt photons are properly accounted for.

Prompt photon overestimation affects flow predictions.

Abstract

The anisotropic emission of direct photons from Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV was calculated using a (3+1)-dimensional viscous hydrodynamic model with the impact parameter Glasma initial condition. The transverse momentum spectra of direct photons in different centrality bins (0-20\%, 20-40\%, and 40-60\%) are in good agreement with experimental data measured at RHIC. For the elliptic flow $v_{2}$ and triangular flow $v_{3}$, the agreement is centrality dependent, showing good correspondence for the 20-40\% bin but underprediction for the 0-20\% bin and overprediction for the 40-60\% bin. After carefully accounting for the contribution from prompt photons, the measured $v_{2}$ of direct photons is no longer too large to explain. An overestimation of the prompt photon yield can suppress the $v_2$ and $v_3$ of direct photons to values lower than those observed in the experimental data.