Medium effects on the relaxation of dissipative flows in a hot pion gas

TL;DR

This paper investigates how medium effects influence the relaxation times of dissipative flows in a hot pion gas, incorporating temperature-dependent cross-sections and chemical potentials to better understand heavy ion collision dynamics.

Contribution

It introduces a temperature-dependent pi-pi cross-section with self-energy corrections and accounts for chemical freeze-out, providing a more realistic calculation of relaxation times.

Findings

Relaxation times are significantly affected by medium modifications.

Temperature dependence alters shear, bulk viscous, and heat flow relaxation times.

Inclusion of chemical potential impacts dissipative flow behavior.

Abstract

The relaxation times over which dissipative fluxes restore their steady state values have been evaluated for a pion gas using the 14-moment method. The effect of the medium has been implemented through a temperature dependent pi-pi cross-section in the collision integral which is obtained by including one-loop self-energies in the propagators of the exchanged rho and sigma mesons. To account for chemical freeze out in heavy ion collisions, a temperature dependent pion chemical potential has been introduced in the distribution function. The temperature dependence of the relaxation times for shear and bulk viscous flows as well as the heat flow is significantly affected.