Natural 2HDMs without FCNCs

TL;DR

This paper introduces two novel flavorful two-Higgs-doublet models (2HDMs) that naturally suppress flavor-changing-neutral-currents and predict distinctive Yukawa coupling deviations, with potential tests at the LHC.

Contribution

It proposes two new 2HDM scenarios, Type-A and B, linking fermion masses to a unique Higgs doublet and avoiding FCNCs, expanding the phenomenological landscape.

Findings

Distinctive Yukawa coupling deviations for light fermions predicted

Potential LHC signatures include $h o J/\Psi + \gamma$, $h o\mu\mu$, and muon pair resonances

Models can be distinguished from conventional 2HDMs through specific decay searches

Abstract

Motivated by the fermion mass hierarchy we study the phenomenology of two flavorful two-Higgs-doublet model (2HDM) scenarios. By virtue of the flavor or singular alignment ansatz it is possible to link the mass of a subset of fermions to the vacuum-expectation-value (VEV) of a unique Higgs doublet and to simultaneously avoid flavor-changing-neutral-currents at tree-level. We explicitly construct two models called Type-A and B. There, either the top quark alone or all third generation fermions couple to the doublet with the larger VEV. The other fermions acquire their masses through the small VEV of the other doublet. Thus, more natural values for the Yukawa couplings can be obtained. The main differences between these models and conventional ones are studied including a discussion of both their structure and phenomenological consequences. In particular, as distinctive deviations for the Yukawa couplings of the light fermions are predicted we discuss possible tests at the LHC based on searches for $h\to J/\Psi + \gamma$, $h\to\mu\mu$, and heavy scalar resonances decaying to muon pairs. We find that for a wide region of parameter space this specific set of signatures can be used to distinguish among the new proposed types and the conventional ones.