Bound on the anomalous tbW coupling from two-loop contribution to neutron electric dipole moment

Abstract

The two-loop contribution to the electric dipole moment (EDM) and the chromo-electric dipole moment (CEDM) of an arbitrary fermion f induced by the most general renormalizable tbW coupling with complex left- and right-handed components ( a L and a R ) is calculated. The analytical expressions are numerically evaluated and the current experimental constraints on the electron, neutron and mercury atom EDMs are used to obtain a bound on the complex phase Im ( a L ∗ a R ) . It is found that the most stringent constraint, Im ( a L ∗ a R ) < 2.33 × 10 −2 , arises from the neutron EDM.