The nature of the Roberge-Weiss transition in $N_f=2$ QCD with Wilson fermions

Abstract: At imaginary values of the quark chemical potential $\mu$, Quantum Chromodynamics shows an interesting phase structure due to an exact center, or Roberge-Weiss (RW), symmetry. This can be used to constrain QCD at real $\mu$, where the sign problem prevents Monte Carlo simulations of the lattice theory. In previous studies of this region with staggered fermions it was found that the RW endpoint, where the center transition changes from first-order to a crossover, depends non-trivially on the quark mass: for high and low masses, it is a triple point connecting to the deconfinement and chiral transitions, respectively, changing to a second-order endpoint for intermediate mass values. These parameter regions are separated by tricritical points. Here we present a confirmation of these findings using Wilson fermions on $N_\tau=4$ lattices. In addition, our results provide a successful quantitative check for a heavy quark effective lattice theory at finite density.