Viscosity and boost invariance at RHIC and LHC

TL;DR

This paper investigates how shear viscosity influences the longitudinal hydrodynamic evolution in relativistic heavy-ion collisions at RHIC and LHC, affecting energy density requirements and rapidity distribution features.

Contribution

It provides new insights into the role of shear viscosity in hydrodynamic models, showing its impact on energy density estimates and rapidity plateau preservation.

Findings

Shear viscosity reduces the cooling rate of the system.

Shear viscosity decreases the initial energy density needed at RHIC.

Shear viscosity helps maintain the Bjorken plateau at LHC.

Abstract

We consider the longitudinal hydrodynamic evolution of the fireball created in a relativistic heavy-ion collision. Nonzero shear viscosity reduces the colling rate of the system and hinders the acceleration of the longitudinal flow. As a consequence, the initial energy density needed to reproduce the experimental data at RHIC energies is significantly reduced. At LHC energies, we expect that shear viscosity helps to conserve a Bjorken plateau in the rapidity distributions during the expansion.