The QCD equation of state from improved staggered fermions

TL;DR

This paper computes the QCD equation of state at finite temperature using improved staggered fermions on lattices with N_tau=8, comparing different actions and analyzing deconfinement and chiral transition behaviors.

Contribution

It provides new lattice QCD results for the equation of state with physical quark masses using two improved staggered actions, and compares systematic errors across lattice spacings.

Findings

Good agreement between asqtad and p4 actions.

Deconfinement and chiral restoration occur in a narrow temperature range.

Systematic errors are quantified by comparison with coarser lattices.

Abstract

We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent $N_{\tau}=8$. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two $O(a^2)$ improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is performed to quantify systematic errors in current studies of the equation of state. We also present results for observables that are sensitive to deconfining and chiral aspects of the QCD transition on $N_\tau=6$ and 8 lattices. We find that deconfinement and chiral symmetry restoration happen in the same narrow temperature interval.