Neutron electric dipole moment induced by strangeness revisited

Abstract

We have revisited the calculation of the neutron electric dipole moment in the presence of the $CP$-violating operators up to dimension 5 based on the chiral perturbation theory. In particular, 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 nucleons is small, the contribution of the chromoelectric dipole moment of strange quarks may still be sizable, and thus may offer a sensitive probe for the $CP$-violating interactions in physics beyond the Standard Model.