Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields

TL;DR

This paper develops a lattice QCD method using background electric fields to separately determine nucleon magnetic moments and electric polarizabilities, addressing their interdependence in relativistic nucleon propagation.

Contribution

It introduces a novel combination of correlation functions in background electric fields to isolate magnetic moments and electric polarizabilities in lattice QCD simulations.

Findings

Successfully extracted neutron and proton properties from lattice simulations.

The isovector magnetic moment matches previous lattice measurements at similar pion masses.

Demonstrated the method's effectiveness with dynamical clover fermions on anisotropic gauge configurations.

Abstract

Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. This is analogous to the experimental situation, for which determination of polarizabilities from the Compton amplitude requires subtraction of Born terms. With the background field method, we devise combinations of nucleon correlation functions in constant electric fields that isolate magnetic moments and electric polarizabilities. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how both observables can be determined from lattice QCD simulations in background electric fields. We obtain results for the neutron and proton, however, our study is currently limited to electrically neutral sea quarks. The value we extract for the nucleon isovector magnetic moment is comparable to those obtained from measuring lattice three-point functions at similar pion masses.