Bulk and shear viscosities of matter created in relativistic heavy-ion collisions

TL;DR

This paper investigates how shear and bulk viscosities in the hadronic phase influence the evolution and particle production in relativistic heavy-ion collisions, highlighting their impact on observable flow patterns and freeze-out conditions.

Contribution

It introduces the first calculations of bulk viscosity effects in the hadronic phase and their role in matching experimental particle spectra and flow data.

Findings

Viscosities significantly affect elliptic flow and interferometry radii.

Bulk viscosity helps achieve consistent freeze-out temperatures.

Viscous effects are crucial in late-stage fireball evolution.

Abstract

We study the effects of the shear and bulk viscosities in the hadronic phase on the expansion of the fireball and on the particle production in relativistic heavy ion collisions. Comparing simulation with or without viscosity in the hadronic matter we find that elliptic flow observables strongly dependent on dissipative effects in the late stage. On the other hand, interferometry radii are sensitive, through the early transverse flow, on the value of the viscosity at high temperatures. We present first calculations including the effects of bulk viscosity in the hadronic phase and in the hadron emission. We find them important in obtaining a small freeze-out temperature consistent with the measured transverse momentum spectra and elliptic flow of identified particles.