CP-violation in Compton scattering

TL;DR

This paper explores how CP violation affects Compton scattering on nucleons, introducing new parameters to describe T-violating responses and estimating their values with effective field theory.

Contribution

It constructs a CP-violating Compton tensor, introduces T-odd nucleon polarizabilities, and provides a HBChPT estimate for these new parameters.

Findings

Defined T-odd nucleon polarizabilities

Separated Born and non-Born contributions

Estimated polarizabilities using HBChPT

Abstract

I consider Compton scattering off the nucleon in the presence of $CP$ violation. I construct the Compton tensor which possesses these features and consider low energy expansion (LEX) of the corresponding amplitudes. It allows to separate out the Born contribution which only depends on the static properties of the nucleon, such as the electric charge, the mass, the magnetic moment, and the electric dipole moment (EDM). I introduce new structure constants, the $T$-odd nucleon polarizabilities which parametrize the unknown non-Born part. These constants describe the response of the $T$-violating content of the nucleon to the external quasistatic electromagnetic field. As an estimate, I provide a HBChPT calculation for these new polarizabilities and discuss the implications for the experiment.