Top Down Electroweak Dipole Operators

Abstract

We derive present constraints on, and prospective sensitivity to, the electric dipole moment (EDM) of the top quark (d_t) implied by searches for the EDMs of the electron and nucleons. Above the electroweak scale v, the d_t arises from two gauge invariant operators generated at a scale Λ≫v that also mix with the light fermion EDMs under renormalization group evolution at two-loop order. Bounds on the EDMs of first generation fermion systems thus imply bounds on |d_t|. Working in the leading log-squared approximation, we find that the present upper bound on |d_t| is 10^(−19) e cm for Λ=1 TeV, except in regions of finely tuned cancellations that allow for |d_t| to be up to fifty times larger. Future d_e and d_n probes may yield an order of magnitude increase in d_t sensitivity, while inclusion of a prospective proton EDM search may lead to an additional increase in reach.

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