Rare $B$ decays at CMS including $B$ di-muonic decays

The rare decays $B_s(B^0) \rightarrow \mu^+\mu^-$ are an excellent test of the flavor sector of the Standard Model and provide sensitivity to models with extended Higgs boson sectors. We report on searches for these decays with the CMS experiment using $pp$ collisions at a centre-of-mass energy $\sqrt{s}=7~\mathrm{TeV}$ collected in 2011. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are ${\mathfrak B}(B^0_s \rightarrow \mu^+ \mu^-) < 7.7 \times 10^{-9}$ and ${\mathfrak B}(B^0_d \rightarrow \mu^+ \mu^-) < 1.8 \times 10^{-9}$ at 95\% confidence level.