Large $h\to b s$ in generic two-Higgs-doublet models

TL;DR

This paper explores the potential for large $h\to bs$ decay rates in generic two-Higgs-doublet models, identifying parameter regions where the decay can exceed 10% without conflicting with existing constraints, and discussing implications for collider searches.

Contribution

It demonstrates that sizable $h\to bs$ decay rates are possible in two-Higgs-doublet models with tuned parameters, expanding the understanding of flavor-violating Higgs decays.

Findings

$h\to bs$ branching ratio can exceed 10% in certain parameter regions.

Tuning of scalar masses and couplings is necessary to satisfy all experimental constraints.

$h\to bs$ can impact Higgs search strategies and indicate additional scalar resonances.

Abstract

We investigate the possible size of $h\to bs$ in two-Higgs-doublet models with generic Yukawa couplings. Even though the corresponding rates are in general expected to be small due to the indirect constraints from $B_s\to\mu^{+}\mu^{-}$ and $B_s$--$\overline{B}_s$ mixing, we find regions in parameter space where $h\to bs$ can have a sizable branching ratio well above 10\%. This requires a tuning of the neutral scalar masses and their couplings to muons, but then all additional constraints such as $B\to X_s \gamma$, $(g-2)_\mu$, and $h\to\mu^{+}\mu^{-}$ are satisfied. In this case, $h\to bs$ can be a relevant background in $h\to b\bar{b}$ searches and vice versa due to the imperfect $b$-tagging purity. Furthermore, if $h\to bs$ is sizeable, one expects two more scalar resonances in the proximity of $m_h$. We briefly comment on other flavour violating Higgs decays and on the 95 GeV $\gamma\gamma$ resonance within generic two-Higgs-doublet models.