Finding the CP-Violating Higgs Bosons at e^+e^- Colliders

TL;DR

This paper analyzes a general two-Higgs-doublet model with CP violation, deriving sum rules that ensure at least one neutral Higgs boson can be detected at e^+e^- colliders through various production channels, regardless of mixing angles and masses.

Contribution

It introduces a new sum rule linking Yukawa and Higgs-Z couplings, guaranteeing detectability of neutral Higgs bosons in e^+e^- colliders despite CP-violating mixing.

Findings

A neutral Higgs boson cannot escape detection if kinematically accessible in key production modes.

Sum rules are modified when the Higgs sector includes additional singlets.

Detection prospects are robust across different mixing scenarios and mass spectra.

Abstract

We discuss a general two-Higgs-doublet model with CP violation in the Higgs sector. In general, the three neutral Higgs fields of the model all mix and the resulting physical Higgs bosons have no definite CP properties. We derive a new sum rule relating Yukawa and Higgs-Z couplings which implies that a neutral Higgs boson cannot escape detection at an e^+e^- collider if it is kinematically accessible in Z+Higgs, $b\anti b+$Higgs and $t\anti t+$Higgs production, irrespective of the mixing angles and the masses of the other neutral Higgs bosons. We also discuss modifications of the sum rules and their phenomenological consequences in the case when the two-doublet Higgs sector is extended by adding one or more singlets.