Vacuum Induced CP Violation Generating a Complex CKM Matrix with Controlled Scalar FCNC

TL;DR

This paper introduces a minimal Two Higgs Doublet Model with spontaneous CP violation that naturally generates a complex CKM matrix and predicts scalar FCNCs, with implications for LHC and ILC experiments.

Contribution

It presents a viable model linking vacuum CP violation to a complex CKM matrix and scalar FCNCs, with detailed phenomenological analysis and experimental predictions.

Findings

Scalar sector scalars are lighter than 1 TeV.

Model reproduces observed CP violation in CKM matrix.

Predicts observable flavor-changing Higgs decays at colliders.

Abstract

We propose a viable minimal model with spontaneous CP violation in the framework of a Two Higgs Doublet Model. The model is based on a generalised Branco-Grimus-Lavoura model with a flavoured $\mathbb{Z}_2$ symmetry, under which two of the quark families are even and the third one is odd. The lagrangian respects CP invariance, but the vacuum has a CP violating phase, which is able to generate a complex CKM matrix, with the rephasing invariant strength of CP violation compatible with experiment. The question of scalar mediated flavour changing neutral couplings is carefully studied. In particular we point out a deep connection between the generation of a complex CKM matrix from a vacuum phase and the appearance of scalar FCNC. The scalar sector is presented in detail, showing that the new scalars are necessarily lighter than 1 TeV. A complete analysis of the model including the most relevant constraints is performed, showing that it is viable and that it has definite implications for the observation of New Physics signals in, for example, flavour changing Higgs decays or the discovery of the new scalars at the LHC. We give special emphasis to processes like $t\to {\rm h} c,{\rm h} u$, as well as ${\rm h}\to bs, bd$, which are relevant for the LHC and the ILC.