Electric Dipole Moments in Two-Higgs-Doublet Models

TL;DR

This paper reevaluates constraints on CP violation in two-Higgs-doublet models using electric dipole moments, finding that current bounds are strong but can be mitigated by cancellations, with future experiments poised to detect such effects.

Contribution

It provides a comprehensive analysis of electric dipole moment constraints in two-Higgs-doublet models, including mechanisms that suppress flavor-changing neutral currents.

Findings

Constraints are strong but can be weakened by scalar cancellations.

Parameter space allows for observable effects in upcoming experiments.

Current bounds do not require unnatural parameter smallness.

Abstract

Electric dipole moments are extremely sensitive probes for additional sources of CP violation in new physics models. Specifically, they have been argued in the past to exclude new CP-violating phases in two-Higgs-doublet models. Since recently models including such phases have been discussed widely, we revisit the available constraints in the presence of mechanisms which are typically invoked to evade flavour-changing neutral currents. To that aim, we start by assessing the necessary calculations on the hadronic, nuclear and atomic/molecular level, deriving expressions with conservative error estimates. Their phenomenological analysis in the context of two-Higgs-doublet models yields strong constraints, in some cases weakened by a cancellation mechanism among contributions from neutral scalars. While the corresponding parameter combinations do not yet have to be unnaturally small, the constraints are likely to preclude large effects in other CP-violating observables. Nevertheless, the generically expected contributions to electric dipole moments in this class of models lie within the projected sensitivity of the next-generation experiments.