Calculation of Nucleon Electric Dipole Moments Induced by Quark Chromo-Electric Dipole Moments and the QCD $\theta$-term

TL;DR

This paper discusses lattice QCD calculations of nucleon electric dipole moments induced by the QCD $ heta$-term and quark chromo-EDMs, addressing computational challenges and feasibility at physical quark masses.

Contribution

It presents detailed lattice calculation methods for nucleon EDMs induced by CP-violating interactions using chiral-symmetric fermions, and assesses their feasibility at physical quark masses.

Findings

Lattice techniques for nucleon EDMs are developed and refined.

Feasibility of physical point calculations is evaluated.

Results contribute to understanding CP violation constraints.

Abstract

Electric dipole moments (EDMs) of nucleons and nuclei, which are sought as evidence of CP violation, require lattice calculations to connect constraints from experiments to limits on the strong CP violation within QCD or CP violation introduced by new physics from beyond the standard model. Nucleon EDM calculations on a lattice are notoriously hard due to large statistical noise, chiral symmetry violating effects, and potential mixing of the EDM and the anomalous magnetic moment of the nucleon. In this report, details of ongoing lattice calculations of proton and neutron EDMs induced by the QCD $\theta$-term and the quark chromo-EDM, the lowest-dimension effective CP-violating quark-gluon interaction are presented. Our calculation employs chiral-symmetric fermion discretization. An assessment of feasibility of nucleon EDM calculations at the physical point is discussed.