Constraints on a Class of Two-Higgs Doublet Models with tree level FCNC

TL;DR

This paper investigates a specific class of two-Higgs doublet models with tree-level flavor-changing neutral currents, deriving constraints from various processes and exploring the potential for discovering new scalars within experimental reach.

Contribution

It provides a detailed analysis of FCNC constraints in a class of two-Higgs doublet models with a discrete symmetry, linking FCNC couplings to mixing matrices and scalar VEV ratios.

Findings

Constraints limit scalar masses to accessible ranges

FCNC couplings are determined by mixing matrices and VEV ratios

Potential for discovering new scalars at current experiments

Abstract

We analyse a class of two Higgs doublet models where flavour-changing neutral currents (FCNC) are present at tree level in a mixing-suppressed manner. In this class of models, because of a discrete symmetry imposed on the lagrangian, the FCNC couplings in the quark and lepton sector are fixed in terms of the corresponding mixing matrix (CKM or PMNS), the fermion masses and the ratio $v_2/v_1$ of the vacuum expectation values of the neutral scalars. A large number of processes, including tree and loop level transitions mediated by the new charged or neutral scalars are used as constraints. It is shown that among the interesting phenomenological prospects for these models, the new scalars may have masses within experimental reach.