Locations of Roberge-Weiss transition endpoints in lattice QCD with $N_f=2$ improved KS quarks

TL;DR

This study locates the tricritical points of the Roberge-Weiss transition endpoints in lattice QCD with $N_f=2$ improved KS quarks, revealing their positions across different quark masses using simulations with improved actions.

Contribution

It provides the first detailed determination of the tricritical points of RW transition endpoints in $N_f=2$ lattice QCD with improved actions, across a range of quark masses.

Findings

Two tricritical points are within the ranges 0.024-0.026 and 0.040-0.050 in quark mass.

Simulations used susceptibility and Binder cumulant of the Polyakov loop.

Results suggest the nature of RW endpoints varies with quark mass.

Abstract

Result on the locations of the tricritical points of $N_f=2$ lattice QCD with imaginary chemical potential is presented. Simulations are carried out with Symanzik improved gauge action and Asqtad fermion action. With imaginary chemical potential $i\mu_I=i\pi T$, previous studies show that the Roberge-Weiss (RW) transition endpoints are triple points at both large and small quark masses, and second order transition points at intermediate quark masses. The triple and second order endpoints are separated by two tricritical ones. Our simulations are carried out at 7 values of quark mass $am$ ranging from 0.024 to 0.070 on lattice volume $12^3\times 4, 16^3\times 4,\, 20^3\times4$. The susceptibility and Binder cumulant of the imaginary part of Polyakov loop are employed to determine the nature of RW transition endpoints. The simulations suggest that the two tricritical points are within the range $0.024-0.026$ and $0.040-0.050$, respectively.