Abstract
We derive present constraints on, and prospective sensitivity to, the electric dipole moment (EDM) of the top quark (dt) implied by searches for the EDMs of the electron and nucleons. Above the electroweak scale v, the dt 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 |dt|. Working in the leading log-squared approximation, we find that the present upper bound on |dt| is 10−19e cm for Λ=1 TeV, except in regions of finely tuned cancellations that allow for |dt| to be up to fifty times larger. Future de and dn probes may yield an order of magnitude increase in dt sensitivity, while inclusion of a prospective proton EDM search may lead to an additional increase in reach.
Highlights
The search for physics beyond the Standard Model (BSM) lies at the forefront of both high- and low-energy physics
Top quarks may provide a unique window into BSM physics, given that the top Yukawa coupling is large compared to all other Standard Model (SM) fermions
If it is generated by BSM physics at a scale Λ that lies well above the electroweak scale v = 246 GeV, it is likely that two dimensionsix CPV dipole operators emerge, coupling respectively to the U(1)Y and SU(2)L gauge bosons
Summary
The search for physics beyond the Standard Model (BSM) lies at the forefront of both high- and low-energy physics. If it is generated by BSM physics at a scale Λ that lies well above the electroweak scale v = 246 GeV, it is likely that two dimensionsix CPV dipole operators emerge, coupling respectively to the U(1)Y and SU(2)L gauge bosons. We denote these operators as OtB and OtW , respectively. We will make no a priori assumptions about the relationships between the CtB and CtW at the scale Λ, endeavoring to be as model-independent as possible In these respects, our analysis complements the earlier studies in Refs. We illustrate the potential reach of generation electron and nucleon EDM searches
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