The electric dipole moment of the neutron from Nf = 2+1+1 twisted mass fermions

Abstract

We extract the neutron electric dipole moment (nEDM) dn on configurations produced with Nf = 2+1+1 twisted mass fermions with lattice spacing of a ≃ 0.082fm and a light quark mass that correpsonds to Mπ ≃ 373 MeV. We do so by evaluating the CP-odd form factor F3 for small values of the CP-violation parameter θ in the limit of zero momentum transfer. This limit is extracted using the usual parametrization but in addition position space methods. The topological charge is computed via cooling and gradient flow using the Wilson, Symanzik treelevel improved and Iwasaki actions for smoothing. We obtain consistent results for all choices of smoothing procedures and methods to extract F3 at zero momentum transfer. For the ensemble analyzed we find a value of nEDM of dn/θ = 0.045(6)(1)e · fm.