Systematic parameter study of hadron spectra and elliptic flow from viscous hydrodynamic simulations of Au+Au collisions at sqrt(s_NN) = 200 GeV

TL;DR

This study systematically explores how various parameters in viscous hydrodynamic models affect the simulation of hadron spectra and elliptic flow in gold-gold collisions at high energy, revealing a tension in parameter preferences.

Contribution

It provides a comprehensive analysis of parameter dependencies in viscous hydrodynamics for heavy-ion collisions, highlighting a tension between spectra and flow constraints.

Findings

Proton spectra favor larger eta/s values.

Elliptic flow data prefer smaller eta/s values.

Changing other parameters does not resolve the tension.

Abstract

Using the (2+1)-dimensional viscous hydrodynamic code VISH2+1, we present systematic studies of the dependence of pion and proton transverse momentum spectra and their elliptic flow in 200 A GeV Au+Au collisions on the parameters of the hydrodynamic model (thermalization time, initial entropy density distribution, decoupling temperature, equation of state, and specific shear viscosity eta/s). We identify a tension between the slope of the proton spectra, which (within hydrodynamic simulations that assume a constant shear viscosity to entropy density ratio) prefer larger eta/s values, and the slope of the p_T-dependence of charged hadron elliptic flow, which prefers smaller values of eta/s. Changing other model parameters does not appear to permit dissolution of this tension