Temperature dependence of QGP viscosity over entropy ratio from hydrodynamical analysis of ALICE data in $\sqrt{s_{NN}}$=2.76 TeV Pb+Pb collisions

TL;DR

This study uses hydrodynamical analysis of ALICE data from Pb+Pb collisions at 2.76 TeV to determine the temperature dependence of the quark-gluon plasma's viscosity over entropy ratio, finding it favors weak temperature dependence.

Contribution

It introduces a parameterization of the QGP viscosity over entropy ratio's temperature dependence and constrains it using experimental data from high-energy heavy-ion collisions.

Findings

Data favor a weak temperature dependence of $rac{ta}{s}$ with $lpha$ between 0 and 0.2.

Higher $lpha$ values (>=0.4) are not supported by the data at 2.76 TeV.

Different collision energies suggest different preferred $lpha$ values.

Abstract

Within Israel-Stewart's theory of dissipative hydrodynamics, we have analyzed ALICE data for the centrality dependence of charged particles multiplicity, elliptic flow and $p_T$ spectra in $\sqrt{s}_{NN}$=2.76 TeV Pb+Pb collisions and obtained the temperature dependence of the QGP viscosity over the entropy ratio ($\etas$). If temperature dependence of $\etas$ is parameterized as $\etas=\alpha \frac{T-T_c}{T_c}+\frac{1}{4\pi}$, experimental data favor $\alpha$ in the range 0-0.2. $\alpha \geq 0.4$ is not favored by the data. Experimental data in $\sqrt{s}_{NN}$=200 GeV Au+Au collisions however, prefer $\alpha$=0.4.