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

TL;DR

This paper calculates the two-loop contributions of a general tbW coupling to fermion EDMs and uses experimental data to set bounds on the coupling's complex phase, with the neutron EDM providing the strongest constraint.

Contribution

It provides the first analytical calculation of two-loop induced EDMs from a general tbW coupling and derives experimental bounds on its complex phase.

Findings

Neutron EDM constrains Im(a^*_La_R) < 2.33 x 10^{-2}

Analytical expressions for two-loop EDM contributions are obtained

Current experimental EDM limits restrict the phase of the tbW coupling

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^*_La_R). It is found that the most stringent constraint, Im(a^*_La_R)<2.33 X 10^{-2}, arises from the neutron EDM.