Self-consistent conversion of a one-component bulk viscous fluid to particles

TL;DR

This paper develops a self-consistent method for converting a bulk viscous fluid into particles in heavy-ion collision simulations, improving the accuracy of fluid-to-particle conversion by incorporating kinetic theory corrections.

Contribution

It introduces a kinetic theory-based bulk viscous correction for a one-component system, comparing it to existing methods and analyzing its impact on elliptic flow predictions.

Findings

Bulk viscous corrections differ from Grad and relaxation time approximations.

Calculated bulk viscosity aligns with theoretical expectations.

Bulk correction choices influence elliptic flow predictions.

Abstract

Comparison of heavy-ion experiments to fluid dynamics simulations requires the conversion of the fluid to particles. Extending the approach in Molnar & Wolff, PRC 95, 024903 (2017), this work presents self-consistent bulk viscous corrections from kinetic theory for a one-component system with isotropic $2\to 2$ interactions. The phase space corrections are contrasted to the Grad ansatz and also to corrections obtained from the relaxation time approximation. In addition, the bulk viscosity of the system is calculated and compared with the Grad result, as well as the $\zeta \propto (1 - 3 c_s^2)^2 \eta$ relation between shear and bulk viscosity near the conformal limit. The possible influence of various bulk correction choices on differential elliptic flow $v_2(p_T)$ in heavy-ion collisions is also estimated.