Higgs search and flavor-safe fermion mass generation

TL;DR

This paper explores a Higgs-like scalar in a flavor-safe fermion mass generation scenario, analyzing flavor constraints, collider phenomenology, and the impact on Higgs search channels, especially in the context of electroweak symmetry breaking with a fermiophobic component.

Contribution

It introduces a model where electroweak symmetry breaking involves a fermiophobic sector, examines flavor constraints, and studies the phenomenology of a light scalar with modified couplings.

Findings

Neutral meson mixing constrains the model significantly.

A factor of two enhancement in top Yukawa is allowed for heavy charged scalars.

Destructive interference suppresses the di-photon signal of the light scalar.

Abstract

We study a scenario of electroweak symmetry breaking where the weak gauge boson masses arises significantly from a fermiophobic source. To minimize flavor violation, the fermion mass generation is still due to one light doublet scalar. One of the realizations is the Bosonic Technicolor model. In these scenarios, the Yukawa couplings between the light scalar and the standard model fermions are in general enhanced while the couplings between the light scalar and weak gauge bosons are reduced. Even though the flavor violation induced by the neutral scalar at the tree level can be avoided, the charged scalar state inevitably mediate flavor changing neutral current processes. With the enhancement in the Yukawa couplings, one expects serious constraints of such models from flavor violating effects. We find that the most severe bound comes from neutral meson mixing of $B^{0}_{d}-\bar{B^{0}_{d}}$. Large parameter space is excluded if the weak gauge boson mass generation is dominated by the fermophobic sector. However, the correlation between the Yukawa coupling and charged scalar mass show that a factor of two enhancement in top Yukawa coupling is still allowed for charged scalar heavier than 500 GeV. We use this as a benchmark point to study the phenomenology of the light scalar. It is interesting that the destructive interference between the top quark loop and the $W$-boson loop in the di-photon channel becomes significant and makes the channel negligible. In the light scalar region, the search becomes much more challenging than the conventional SM Higgs boson.