Hydrodynamic simulations of relativistic heavy-ion collisions with different lattice QCD calculations of the equation of state

TL;DR

This study compares hydrodynamic simulations of heavy-ion collisions using three different lattice QCD equations of state, finding minimal differences between some and significant variations with others, impacting the interpretation of experimental data.

Contribution

It introduces a systematic comparison of multiple lattice QCD equations of state in hydrodynamic models of heavy-ion collisions, highlighting their effects on observable predictions.

Findings

Stout and HISQ/tree equations of state produce similar results within a few percent.

The s95p-v1 equation of state results in 10-20% differences in spectra and flow.

Sampling the HISQ/tree EoS from error distributions yields minimal differences.

Abstract

Hydrodynamic calculations of ultra-relativistic heavy ion collisions are performed using the iEBE-VISHNU 2+1D code with fluctuating initial conditions and three different parameterizations of the Lattice QCD equations of state: continuum extrapolations for stout and HISQ/tree actions, as well as the s95p-v1 parameterization based upon calculations using the p4 action. All parameterizations are matched to a hadron resonance gas equation of state at T = 155 MeV, at which point the calculations are continued using the UrQMD hadronic cascade. Calculations for $\sqrt{s_{NN}}=200$ GeV Au+Au collisions in three centrality classes are compared to experimental data for final state particle spectra and anisotropic flow coefficients $v_2$ and $v_3$ as well as for pion HBT radii. Experimental observables for the stout and HISQ/tree equations of state are observed to differ by less than a few percent for all observables, while the s95p-v1 equation of state generates spectra and flow coefficients which differ by ~10-20%. Calculations in which the HISQ/tree equation of state is sampled from the published error distribution are also observed to differ by less than a few percent.