Temperature dependence of η/s of strongly interacting matter : effects of the equation of state and the parametric form of (η/s)(T)

Abstract

We investigate the temperature dependence of the shear viscosity to entropy density ratio η/s using a piecewise linear parametrization. To determine the optimal values of the parameters and the associated uncertainties, we perform a global Bayesian model-to-data comparison on Au+Au collisions at √sNN=200 GeV and Pb+Pb collisions at 2.76 TeV and 5.02 TeV, using a 2+1D hydrodynamical model with the Eskola-Kajantie-Ruuskanen-Tuominen (EKRT) initial state. We provide three new parametrizations of the equation of state (EoS) based on contemporary lattice results and hadron resonance gas, and use them and the widely used s95p parametrization to explore the uncertainty in the analysis due to the choice of the equation of state. We find that η/s is most constrained in the temperature range T≈150–220 MeV, where, for all EoSs, 0.08