Flavor-Violating Higgs and Top Decays in the Type 1B Flavorful Two-Higgs-Doublet Model with a Twist

Abstract

We study flavor-violating decays of the SM-like Higgs boson and rare top decays in the Type 1B realization of the flavorful two-Higgs-doublet model with a twist, focusing on $h\to sb$, $h\to db$, $h\to uc$, $h\to \mu \tau$, $h\to e\tau$, $h\to e\mu$, $t\to ch$, and $t\to uh$. We present the relevant amplitude and branching-ratio formulae, include one-loop vertex corrections, and impose constraints from Higgs signal-strength measurements, electroweak precision tests, meson mixing, $B\to X_s\gamma$, direct HFV searches and CLFV constraints, including $\mu -e$ conversion. The surviving parameter space favors $\mathrm{BR}(h\to sb)\gg \mathrm{BR}(h\to db)$, $\mathrm{BR}(t\to ch)\gg \mathrm{BR}(t\to uh)$, and $\mathrm{BR}(h\to \mu \tau )\gg \mathrm{BR}(h\to e\tau )\sim \mathrm{BR}(h\to e\mu )$ in the lepton sector. One-loop effects usually preserve these hierarchies, but can modify individual channels through different mechanisms: sizable destructive tree--loop interference can reduce $h\to sb$ enough to yield rare ${\mathrm{BR}}_{1L}(h\to db)>{\mathrm{BR}}_{1L}(h\to sb)$ points, whereas the large relative corrections found in rare top decays mainly reflect strong SM-like alignment suppressing the tree-level amplitudes.

Accepted for publication in Physical Review D