Generalized CP Invariance and the Yukawa sector of Two-Higgs Models

TL;DR

This paper explores generalized CP symmetries in two-Higgs doublet models, revealing that most symmetries lead to massless fermions, except for one model that exhibits a novel form of spontaneous CP violation in the fermion sector.

Contribution

It extends the analysis of CP symmetries to the fermion sector and identifies a unique model with spontaneous CP violation occurring in fermions rather than scalars.

Findings

Most generalized CP symmetries imply massless fermions.

A unique model allows realistic fermion masses.

Spontaneous CP violation occurs in the fermion sector, not the scalar sector.

Abstract

We analyze generalized CP symmetries of two-Higgs doublet models, extending them from the scalar to the fermion sector of the theory. We show that, with a single exception, those symmetries imply massless fermions. The single model which accommodates a fermionic mass spectrum compatible with experimental data possesses a remarkable feature. It displays a new type of spontaneous CP violation, which occurs not in the scalar sector responsible for the symmetry breaking mechanism but, rather, in the fermion sector.