Comparison of results from a 2+1D relativistic viscous hydrodynamic model to elliptic and hexadecapole flow of charged hadrons measured in Au-Au collisions at $\sqrt{s_{\rm {NN}}}$ = 200 GeV

TL;DR

This study compares hydrodynamic model results with experimental data on flow and particle yields in gold-gold collisions at 200 GeV, exploring initial condition effects and shear viscosity estimates.

Contribution

It provides a detailed comparison of viscous hydrodynamic simulations with experimental flow data, highlighting the impact of initial conditions and constraining the shear viscosity to entropy density ratio.

Findings

Shear viscosity to entropy density ratio ($s$) between 0 and 0.12 fits the data.

Glauber initial conditions require lower $s$ than CGC for matching elliptic flow.

Estimated $s$ varies with collision centrality and flow harmonic.

Abstract

Simulated results from a 2+1D relativistic viscous hydrodynamic model have been compared to the experimental data on the centrality dependence of invariant yield, elliptic flow ($v_{2}$), and hexadecapole flow ($v_{4}$) as a function of transverse momentum ($p_{T}$) of charged hadrons in Au-Au collisions at $\sqrt{s_{\rm {NN}}}$ = 200 GeV. Results from two types of initial transverse energy density profile, one based on the Glauber model and other based on Color-Glass-Condensate (CGC) are presented. We observe no difference in the simulated results on the invariant yield of charged hadrons for the calculations with different initial conditions. The comparison to the experimental data on invariant yield of charged hadrons supports a shear viscosity to entropy density ratio ($\eta/s$) between 0 to 0.12 for the 0-10% to 40-50% collision centralities. The simulated $v_{2}(p_{T})$ is found to be higher for a fluid with CGC based initial condition compared to Glauber based initial condition for a given collision centrality. Consequently the Glauber based calculations when compared to the experimental data requires a lower value of $\eta/s$ relative to CGC based calculations. In addition, a centrality dependence of the estimated $\eta/s$ is observed from the $v_{2}(p_{T})$ study. The $v_{4}(p_{T})$ for the collision centralities 0-10% to 40-50% supports a $\eta/s$ value between 0 - 0.08 for a CGC based initial condition. While simulated results using the Glauber based initial condition for the ideal fluid evolution under estimates the $v_{4}(p_{T})$ for collision centralities 0-10% to 30-40%.