The calculations of Nucleon Electric Dipole Moment using background field on Lattice QCD

TL;DR

This paper calculates the neutron electric dipole moment using lattice QCD with background fields, employing gradient flow to control divergences, and provides results relevant for understanding CP violation beyond the Standard Model.

Contribution

It introduces a method to extract the neutron EDM on the lattice using background fields and gradient flow to address UV divergences, applied to specific gauge ensembles.

Findings

Neutron EDM measured with background field method.

Gradient flow reduces UV divergence effects.

Results obtained at specific lattice parameters.

Abstract

Measurements of nucleon and nuclei Electric Dipole Moments (EDMs) play an important role in probing CP violation and exploring physics beyond the Standard Model. We extract the neutron EDM by measuring the energy shift of the nucleon two-point correlation function in the presence of a background field. The UV divergence of the topological charge density operator is mitigated using gradient flow, and the diffusion effect induced by the gradient flow process is included into the fit ansatz. Our calculations were carried out on two 2+1 DWF fermion, Iwasaki, gauge field ensembles generated by the RBC/UKQCD collaborations with inverse lattice spacing 1.73 GeV and pion masses of about 340 and 420 MeV.