Quark Mass and Flavour Dependence of the QCD Phase Transition

TL;DR

This study investigates how quark mass and flavor influence the QCD phase transition temperature, revealing that the transition temperature varies with meson mass and flavor number, and examining screening effects near the transition.

Contribution

It provides new quantitative insights into the dependence of the QCD transition temperature on quark mass and flavor, including extrapolations to the chiral limit and analysis of screening effects.

Findings

Transition temperature controlled by gluonic sector for m_PS > 2 GeV

Pseudo-critical temperature decreases with decreasing m_PS

Transition temperature is about 10% higher in 2-flavour than 3-flavour QCD

Abstract

We analyze the quark mass and flavour dependence of the QCD phase transition temperature. When the lightest pseudo-scalar meson mass (m_PS) is larger than 2 GeV the critical temperature is controlled by the gluonic sector of QCD alone. For smaller values of the lightest meson mass the pseudo-critical temperature decreases slowly with m_PS. For a large regime of meson masses the pseudo-critical temperature of 2-flavour QCD is about 10% larger than in the 3-flavour case. On lattices with temporal extent N_t=4 an extrapolation to the chiral limit yields T_c = 173(8) MeV and 154(8) MeV for 2 and 3-flavour QCD, respectively. We also analyze dynamical quark mass effects on the screening of the heavy quark potential. A detailed analysis of the heavy quark free energy in 3-flavour QCD shows that close to T_c screening effects are approximately quark mass independent already for pseudo-scalar meson masses m_PS = 800 MeV and screening sets in at distances r = 0.3 fm.