Quark mass and flavour dependence of the QCD phase transition Original Research Article

We analyze the quark mass and flavour dependence of the QCD phase transition temperature. When the lightest pseudo-scalar meson mass (mPS) 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 mPS. 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 Nτ=4 an extrapolation to the chiral limit yields Tc=(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 Tc screening effects are approximately quark mass independent already for pseudo-scalar meson masses mPS≲800 MeV and screening sets in at distances r≃0.3 fm.