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

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* aR)- It is found that the most stringent constraint, Im(a(L)*a(R)) < 2.33 x 10(-2), L arises from the neutron EDM. (c) 2007 Elsevier B.V. All rights reserved.