Lattice-based equation of state at finite baryon number, electric charge, and strangeness chemical potentials

Abstract

We construct an equation of state for quantum chromodynamics (QCD) at finite temperature and chemical potentials for baryon number B, electric charge Q, and strangeness S. We use the Taylor expansion method to the fourth power for the chemical potentials. This requires the knowledge of all diagonal and nondiagonal BQS correlators up to fourth order: These results recently became available from lattice QCD simulations, albeit only at a finite lattice spacing Nt=12. We smoothly merge these results to the hadron resonance gas as model, to be able to reach temperatures as low as 30 MeV; in the high-temperature regime, we impose a smooth approach to the Stefan-Boltzmann limit. We provide a parametrization for each one of these BQS correlators as functions of the temperature. We then calculate pressure, energy density, entropy density, baryonic, strangeness, and electric charge densities and compare the two cases of strangeness neutrality and μS=μQ=0. Finally, we calculate the isentropic trajectories and the speed of sound and compare them in the two cases. Our equation of state can be readily used as an input of hydrodynamical simulations of matter created at the Relativistic Heavy Ion Collider.