Topological susceptibility and ${\eta }^{\prime }$ meson mass from $N_f=2$ lattice QCD at the physical point

Abstract

In this paper we explore the computation of topological susceptibility and ${\eta }^{\prime }$ meson mass in $N_f=2$ flavor QCD using lattice techniques with physical value of the pion mass as well as larger pion mass values. We observe that the physical point can be reached without a significant increase in the statistical noise. The mass of the ${\eta }^{\prime }$ meson can be obtained from both fermionic two point functions and topological charge density correlation functions, giving compatible results. With the pion mass dependence of the ${\eta }^{\prime }$ mass being flat we arrive at $M_{{\eta }^{\prime }}=772(18)\mathrm{MeV}$ without an explicit continuum limit. For the topological susceptibility we observe a linear dependence on $M_{\pi }^2$, however, with an additional constant stemming from lattice artifacts.

Comments: 24 pages, 11 figures; matching version accepted for publication