Finite Temperature Transition in Two Flavor QCD with Renormalization Group Improved Action

The nite temperature transition or crossover in QCD with two degenerate Wilson quarks is investigated using a renormalization group improved action. At = 2:0 and 2.1 where a 1 1:0 1:2 GeV, the expectation value of the Polyakov loop and the pion screening mass on an 8 4 lattice vary smoothly with the hopping parameter through the transition/crossover. The quark screening mass in the high temperature phase agrees well with that in the low temperature phase calculated on an 8 lattice. The smooth transition of the observables is totally di erent from the sharp transition found for the standard action at = 5:0 and 5.1 where a 1 is also 1:0 1:2 GeV.