Limiting FCNC induced by a CP symmetry of order 4

TL;DR

This paper investigates whether the CP4 3HDM, a three-Higgs-doublet model with a specific CP symmetry, can suppress flavor-changing neutral currents to align with experimental constraints, providing a systematic analysis of its Yukawa sectors.

Contribution

The study develops an efficient scanning method to analyze FCNC effects in all Yukawa sectors of the CP4 3HDM, identifying only two scenarios compatible with meson oscillation constraints.

Findings

Only two of eight Yukawa sectors satisfy meson oscillation constraints.

The developed scanning procedure links FCNC matrices to physical quark observables.

Guidelines for future phenomenological analyses of CP4 3HDM are provided.

Abstract

CP4 3HDM is a three-Higgs-doublet model based on the $CP$ symmetry of order 4 (CP4). Imposing CP4 leads to remarkable connections between the scalar and Yukawa sectors and unavoidably generates tree-level flavor-changing neutral couplings (FCNC). It remains unclear whether FCNC can be sufficiently suppressed in the CP4 3HDM. In this paper, we systematically explore this issue. We first develop an efficient scanning procedure which takes the quark masses and mixing as input and expresses the FCNC matrices in terms of physical quark observables and quark rotation parameters. This procedure allows us to explore the FCNC effects for all the Yukawa sectors possible within the CP4 3HDM. We find that, out of the eight possible CP4 Yukawa sectors, only two scenarios are compatible with the $K$, $B$, $B_s$ and, in particular, $D$-meson oscillation constraints. The results of this work serve as clear guidelines for future phenomenological scans of the model.