Rare Leptonic B decays

TL;DR

This paper reviews the theoretical understanding of rare leptonic B decays, especially $B_{s} ightarrow au^+ au^-$, highlighting their sensitivity to New Physics and discussing strategies to distinguish different NP models.

Contribution

It provides a comprehensive overview of the theoretical status of rare leptonic B decays and proposes methods to differentiate between various New Physics scenarios.

Findings

Current experimental measurements agree with the Standard Model.

Strategies are proposed to discriminate between different New Physics models.

Discussion on the impact of CP-violating phases on decay observables.

Abstract

The transitions $B_{s,d}\rightarrow \ell^+\ell^-$ (for $\ell=e, \mu, \tau$), although extremely suppressed within the SM, are exceptionally clean channels particularly sensitive to New Physics contributions. So far only the branching ratio for the process $B_{s}\rightarrow \mu^+\mu^-$ has been measured experimentally and, although the results are in agreement with the SM prediction, there is still room for NP effects. Here we provide an overview of the theoretical status of rare decays. We present strategies that can allow us to discriminate between different NP scenarios. Finally, we include a discussion of the effects of nontrivial new CP violating phases on the observables associated with $B_{s}\rightarrow \mu^+\mu^-$.