Effects of bulk viscosity on hadron spectra and Hanbury-Brown Twiss radius by the causal viscous hydrodynamics

TL;DR

This paper investigates how bulk viscosity influences particle spectra and HBT radii in heavy-ion collisions using causal viscous hydrodynamics, revealing that increased bulk viscosity slightly steepens spectra and modifies HBT radius ratios.

Contribution

It introduces a hydrodynamical model incorporating both shear and bulk viscosities to study their effects on observables in heavy-ion collisions.

Findings

Bulk viscosity slightly steepens particle spectra.

Bulk viscosity affects the ratio of HBT radii $R_{out}/R_{side}$.

The model aligns with experimental observations of spectra and HBT measurements.

Abstract

The particle spectra and Hanbury-Brown Twiss (HBT) radius of Au+Au collisions at RHIC energy are investigated by a hydrodynamical expanding source with both shear and bulk viscosities ($\zeta$). With a large width of the ratio of $\zeta$ to entropy density $s$, both the particle transverse momentum spectra and the ratio $R_{out}/R_{side}$ of HBT radii in the direction of the total transverse momentum of detected two particles ($R_{out}$) and perpendicular to both this direction and the beam direction ($R_{side}$) become a little steeper.