Thermal and viscous dissipation in relativistic heavy ion collisions

TL;DR

This paper develops advanced second-order dissipative hydrodynamics equations incorporating heat-shear couplings to study the evolution of high baryon density matter in relativistic heavy ion collisions, revealing energy-dependent dissipation effects.

Contribution

It introduces new relativistic dissipative hydrodynamics equations derived from kinetic theory with heat-shear couplings, applied to non-boost-invariant simulations of heavy ion collisions.

Findings

Thermal dissipation dominates shear pressure at low energies.

Effect of thermal dissipation diminishes at ultra-relativistic energies.

New equations provide more comprehensive modeling of dissipative effects.

Abstract

We investigate the effects of finite baryon density and temperature on the bulk properties of matter formed in relativistic heavy ion collisions within second-order dissipative hydrodynamics. The relativistic fluid evolution equations for heat flow and shear stress tensor are derived from kinetic theory by using Grad's 14-moment approximation for the single-particle phase-space distribution function. The new equations provide a number of additional terms associated with heat-shear couplings as compared to the existing derivations based on entropy principle. The dissipative equations are encoded in non-boost-invariant hydrodynamic model simulation and studied for the evolution of high baryon density matter encountered at the beam energy scan program at RHIC. We find that thermal dissipation dominates shear pressure in defining the bulk observables at the low energy but its effect diminishes at ultra-relativistic energies.