Model building for flavor changing Higgs couplings

TL;DR

This paper explores whether minimal flavor violation and Froggatt-Nielsen models can produce observable flavor-changing Higgs decays without conflicting with existing constraints, finding potential for near-bound signals in specific scenarios.

Contribution

It analyzes the potential of two flavor models to generate detectable flavor-changing Higgs couplings within current experimental limits.

Findings

MFV can produce lepton flavor-changing Higgs couplings near current bounds with heavy neutrino spurions.

FN framework allows large flavor-changing couplings in up and lepton sectors if supersymmetry is involved.

Simple models predict flavor-changing couplings too small for detection without additional mechanisms.

Abstract

If $t\rightarrow hq$ ($q=c,u$) or $h\rightarrow\tau\ell$ ($\ell=\mu,e$) decays are observed, it will be a clear signal of new physics. We investigate whether natural and viable flavor models can saturate the present direct upper bounds without violating the indirect constraints from low energy loop processes. We carry out our analysis in two theoretical frameworks: minimal flavor violation (MFV) and Froggatt-Nielsen symmetry (FN). The simplest models in either framework predict flavor changing couplings that are too small to be directly observed. Yet, in the MFV framework, it is possible to have lepton flavor changing Higgs couplings close to the bound if spurions related to heavy singlet neutrinos play a role. In the FN framework, it is possible to have large flavor changing couplings in both the up and the charged lepton sectors if supersymmetry plays a role.