CP violation in H^\pm \to W^\pm Z: A physical approach for the 2HDM

TL;DR

This paper analyzes CP violation in the decay H^\pm o W^\pm Z within the 2HDM, revealing new sources of CP violation from interference effects and providing a physical coupling-based framework.

Contribution

It introduces a transparent physical approach to CP violation in H^\pm o W^\pm Z decays, identifying additional interference sources and covering both explicit and spontaneous CP violation.

Findings

Qualitative confirmation of interference effects between bosonic and fermionic loops.

Identification of new CP violation sources from internal interference among loop amplitudes.

CP asymmetry manifests as charge asymmetry in inclusive W and Z decays.

Abstract

We investigate CP violation in the process H^\pm \to W^\pm Z within the framework of the two-Higgs-Doublet model (2HDM). Amplitudes are expressed transparently in terms of physical couplings. Our analysis qualitatively confirms recent results by Kanemura and Mura, for the interference between one-loop bosonic and fermionic amplitudes. Furthermore, we identify additional sources of CP violation arising from internal interference among the bosonic and also among the fermionic loop amplitudes. In the alignment limit, the asymmetry would vanish in the absence of fermionic loop contributions when the sum of the masses of the additional neutral scalars is higher than the mass of the Z. Our results allow for generic Yukawa couplings, and cover both explicit and spontaneous CP violation. For inclusive W^\pm and Z decays, the CP violation will only manifest itself as a charge asymmetry.