Post-ACME2013 CP-violation in Higgs Physics and Electroweak Baryogenesis

TL;DR

This paper discusses mechanisms to cancel contributions to the electron EDM from Higgs CP-violation, allowing for viable electroweak baryogenesis despite experimental constraints, and highlights future experimental probes.

Contribution

It introduces cancellation mechanisms in Higgs CP-violation contributions to EDMs, expanding the parameter space for electroweak baryogenesis under current experimental limits.

Findings

Cancellation mechanisms can suppress EDM contributions despite large CP-phases.

Viable electroweak baryogenesis scenarios remain possible with these cancellations.

Future experiments will test these parameter regions.

Abstract

We present a class of cancellation mechanisms to suppress the total contributions of Barr-Zee diagrams to the electron electric dipole moment (eEDM). This class of mechanisms are of particular significance after the new eEDM upper limit, which strongly constrains the allowed magnitude of CP-violation in Higgs couplings and hence the feasibility of electroweak baryogenesis (EWBG), were released by the ACME collaboration in 2013. We point out: if both the CP-odd Higgs-photon-photon ($Z$ boson) and the CP-odd Higgs-electron-positron couplings are turned on, a cancellation may occur either between the contributions of a CP-mixing Higgs boson, with the other Higgs bosons being decoupled, or between the contributions of a CP-even and a CP-odd Higgs bosons. With the assistance of the cancellation mechanisms, a large CP-phase in Higgs couplings with viable electroweak baryogenesis (EWBG) is still allowed. The reopened parameter regions would be probed by the future neutron, mercury EDM measurements, and direct measurements of Higgs CP-properties at the LHC and future colliders.