Bulk viscosity, chemical equilibration and flow at RHIC

TL;DR

This paper investigates how bulk viscosity influences particle spectra and flow in RHIC heavy ion collisions, emphasizing the importance of chemical non-equilibration effects in the hadronic phase for accurate modeling.

Contribution

It demonstrates that incorporating bulk viscosity and chemical non-equilibration effects significantly improves the description of experimental data at RHIC.

Findings

Non-zero bulk viscosity enhances spectra and flow fits.

Chemical non-equilibration dominates viscosity effects.

Bulk viscosity range $ ext{ extbackslash}zeta/s extless 0.05$ is effective.

Abstract

We study the effects of bulk viscosity on p_T spectra and elliptic flow in heavy ion collisions at RHIC. We argue that direct effect of the bulk viscosity on the evolution of the velocity field is small, but corrections to the freezeout distributions can be significant. These effects are dominated by chemical non-equilibration in the hadronic phase. We show that a non-zero bulk viscosity in the range $\zeta/s \lsim 0.05$ improves the description of spectra and flow at RHIC.