Production of thermal photons in a simple chiral-hydrodynamic model

TL;DR

This paper models thermal photon production in heavy-ion collisions using a chiral-hydrodynamic approach, highlighting differences with other models and emphasizing the impact of shear viscosity and dissipative effects.

Contribution

It introduces a self-consistent chiral-hydrodynamic formalism combining the linear sigma model with second-order hydrodynamics for photon spectrum calculations.

Findings

Thermal photon yield is higher in models with temperature-independent shear viscosity.

Slower evolution and larger dissipative effects increase photon production.

Comparison shows significant differences between chiral-hydrodynamic and lattice-based models.

Abstract

We use a self-consistent chiral-hydrodynamic formalism which combines the linear $\sigma$ model with second-order hydrodynamics in 2+1 dimensions to compute the spectrum of thermal photons produced in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The temperature-dependent shear viscosity of the model, $\eta$, is calculated from the linearized Boltzmann equation. We compare the results obtained in the chiral-hydrodynamic model to those obtained in the second-order theory with a Lattice QCD equation of state and a temperature-independent value of $\eta/s$. We find that the thermal photon production is significantly larger in the latter model due to a slower evolution and larger dissipative effects.