Thermodynamics of Four-Flavour QCD with Improved Staggered Fermions

We have calculated the pressure and energy density in four-flavour QCD using improved fermion and gauge actions. We observe a strong reduction of finite cut-off effects in the high temperature regime, similar to what has been noted before for the SU(3) gauge theory. Calculations have been performed on \(16^3\times 4\) and 16^4 lattices for two values of the quark mass, \(ma = 0.05\) and 0.1. A calculation of the string tension at zero temperature yields a critical temperature \(T_c/\sqrt{\sigma} = 0.407 \pm 0.010\) for the smaller quark mass value.