Phase structure and critical temperature of two-flavor QCD with a renormalization group improved gauge action and clover improved Wilson quark action

TL;DR

This study investigates the finite-temperature phase transition of two-flavor QCD using improved lattice actions, identifying a second-order chiral transition and estimating the critical temperature to be approximately 171 MeV.

Contribution

It provides the first lattice study of the phase structure with a renormalization group improved gauge action and clover Wilson quarks, confirming a second-order transition consistent with O(4) universality.

Findings

Identified the parity-broken phase region.

Located the finite-temperature transition line.

Estimated the critical temperature as 171(4) MeV.

Abstract

We study the finite-temperature phase structure and the transition temperature of QCD with two flavors of dynamical quarks on a lattice with the temporal size $N_t=4$, using a renormalization group improved gauge action and the Wilson quark action improved by the clover term. The region of a parity-broken phase is identified, and the finite-temperature transition line is located on a two-dimensional parameter space of the coupling ($\beta=6/g^2$) and hopping parameter $K$. Near the chiral transition point, defined as the crossing point of the critical line of the vanishing pion mass and the line of finite-temperature transition, the system exhibits behavior well described by the scaling exponents of the three-dimensional O(4) spin model. This indicates a second-order chiral transition in the continuum limit. The transition temperature in the chiral limit is estimated to be $T_c = 171(4)$ MeV.