Bounding the minimal 331 model through the decayB→Xsγ

Abstract

We study the decay $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ within the framework of the minimal 331 model, taking into account both new experimental and theoretical developments that allow us to update and improve on an existing 10 yr old analysis. In contrast to several other flavor changing observables that are modified already at tree level from a new ${Z}^{\ensuremath{'}}$ gauge boson, we have only one loop contributions in this case. Nevertheless, these are interesting, as they may be enhanced and can shed light on the charged gauge boson and Higgs sector of the model. Numerically, we find that the Higgs sector, which is well approximated by a 2 Higgs doublet model (2HDM), dominates, since the gauge contributions are already very strongly constrained. With respect to $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$, the signal of the minimal 331 model is therefore nearly identical to the 2HDM one, which allows us to obtain a lower bound on the charged Higgs mass. Further, we observe, in analogy to the 2HDM model, that the branching fraction can be rather strongly increased for small values of $\mathrm{tan}\ensuremath{\beta}$. Also, we find that $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ has no impact on the bounds obtained on rare $K$ and $B$ decays in an earlier analysis.