Effects of the charm quark on the QCD equation of state

TL;DR

This study investigates how including the charm quark affects the QCD equation of state at various temperatures and chemical potentials using lattice simulations, revealing significant effects at high temperatures.

Contribution

It provides the first lattice QCD analysis of charm quark effects on the equation of state at zero and nonzero chemical potential with quenched charm quarks.

Findings

Charm quark significantly influences the equation of state between 1.2T_c and 2T_c.

Contribution at nonzero chemical potential is statistically insignificant.

Results are obtained on lattices with N_t=6 and quenched charm quarks.

Abstract

We study the effects of the addition of the charm quark on the QCD equation of state at zero and nonzero chemical potential on lattices with $N_t=6$. Our ensembles are quenched with respect to charm and the charm quark is a valence staggered quark. Along the trajectory of constant physics the ratio $m_s/m_c$ is kept constant after tuning the charm quark mass at a lattice spacing of about 0.09 fm. We find that the charm quark has a significant contribution to the equation of state at zero chemical potential already at temperatures between about $1.2T_c$ and $2T_c$. The additional contribution at nonzero chemical potential vanishes within the current statistical uncertainty.