Neutron Electric Dipole Moment Induced by the Strangeness Revisited

TL;DR

This paper recalculates the neutron electric dipole moment considering strangeness effects using chiral perturbation theory, lattice QCD, and QCD sum rules, highlighting the potential significance of strange quark contributions in CP violation.

Contribution

It provides a revised analysis of the neutron EDM with a focus on strangeness, combining lattice QCD and QCD sum rules to evaluate relevant matrix elements.

Findings

Strangeness contribution to neutron EDM may be sizable despite small strangeness content.

Chromoelectric dipole moment of strange quark is a sensitive probe for CP violation.

Revised calculations suggest potential for new physics beyond the Standard Model.

Abstract

We have revisited the calculation of the neutron electric dipole moment in the presence of the CP-violating operators up to dimension five based on the chiral perturbation theory. Especially, we focus on the contribution of strangeness content. In the calculation, we extract the nucleon matrix elements of scalar-type quark operators from the results of the lattice QCD simulations, while those of the dipole-type quark-gluon operators are evaluated by using the method of the QCD sum rules. As a result, it is found that although the strangeness quantity in nucleon is small, the contribution of the chromoelectric dipole moment of strange quark may be still sizable, and thus may offer a sensitive probe for the CP-violating interactions in physics beyond the Standard Model.