Abstract
We elucidate a cancellation mechanism for the electric dipole moment of the electron in the general two Higgs doublet model. The impressive improvement by the ACME Collaboration in 2018 suggests the presence of a new electron Yukawa coupling that brings in exquisite cancellations among dangerous diagrams, broadening the solution space for electroweak baryogenesis driven by an extra top Yukawa coupling. The cancellation mechanism calls for the new Yukawa couplings to have hierarchical structures that echo the observed pattern of the Standard Model Yukawa couplings.
Highlights
It is remarkable that the Cabibbo-Kobayashi-Maskawa (CKM) framework is able to explain all laboratory-based measurements of charge-parity, or CP, violation (CPV)
The impressive improvement by the ACME Collaboration in 2018 suggests the presence of a new electron Yukawa coupling that brings in exquisite cancellations among dangerous diagrams, broadening the solution space for electroweak baryogenesis driven by an extra top Yukawa coupling
It is well known that the CPV phase arising from the CKM matrix is by far insufficient in generating the baryon asymmetry of the Universe (BAU); some new CPV phase(s) must exist to address this cosmological problem
Summary
It is remarkable that the Cabibbo-Kobayashi-Maskawa (CKM) framework is able to explain all laboratory-based measurements of charge-parity, or CP, violation (CPV). In a previous paper [3], we have explored the general two Higgs doublet model (g2HDM), i.e., without the ad hoc discrete Z2 symmetry, in which an additional 3 × 3 Yukawa coupling matrix for each type of charged fermion should be CP and flavor violating. The cancellation mechanism works only when the hierarchical structure of the new Yukawa couplings is close to those of the SM Yukawa couplings and with a particular pattern of CPV phases, which may reflect an underlying flavor structure in g2HDM. JðdφeγÞtj would become smaller than the ACME18 bound if jImρttj ≲ 0.01, without changing the value of cγ This would no longer be the ρtt-driven EWBG scenario [3]. We conclude that the ρtt-driven EWBG case as stated above [3] is unlikely to survive the ACME18 bound
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