Pure electroweak mechanism for the electric dipole moment of neutron in the Kobayashi-Maskawa model

Abstract

The pure electroweak three-loop mechanism for the induced electric and chromoelectric dipole moments of quarks is studied in the Kobayashi-Maskawa model with three and four generations. In the standard three generation case, this mechanism is found to produce a negligible contribution to the electric dipole moment of neutron. In the presence of the fourth heavy generation, however, pure electroweak corrections are important and might be several times larger than the corresponding QCD contribution for the masses of heaviest quarks $\sim$ 500-600 GeV. The resulting electric dipole moment of neutron naturally arises at the level of $10^{-29} \,e\cdot cm$. The effects of the fourth generation physics are parametrized at standard electroweak scale by the presence of the effective charged right-handed currents.