Production of thermal photons in viscous fluid dynamics with temperature-dependent shear viscosity

TL;DR

This study calculates thermal photon spectra in heavy-ion collisions using viscous fluid dynamics, highlighting the impact of temperature-dependent shear viscosity in the quark-gluon plasma phase.

Contribution

It introduces a detailed viscous fluid dynamic model incorporating temperature-dependent shear viscosity to analyze thermal photon production.

Findings

Photon spectrum is highly sensitive to shear viscosity in the QGP phase.

Spectrum is nearly insensitive to shear viscosity in the hadronic phase.

Both shear viscosity temperature dependence and equation of state significantly influence photon spectra.

Abstract

We compute the spectrum of thermal photons created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, taking into account dissipative corrections in production processes corresponding to the quark--gluon plasma and hadronic phases. To describe the evolution of the fireball we use a viscous fluid dynamic model with different parametrizations for the temperature--dependence of $\eta/s$. We find that the spectrum significantly depends on the values of $\eta/s$ in the QGP phase, and is almost insensitive to the values in the hadronic phase. We also compare the influence of the temperature--dependence of $\eta/s$ on the spectrum of thermal photons to that of using different equations of state in the fluid dynamic simulations, finding that both effects are of the same order of magnitude.