Search for $B^0_s \to \mu^+\mu^-$ and $B^0 \to \mu^+\mu^-$ with the CMS experiment

The rare decays $B^0_s \to \mu^+\mu^-$ and $B^0 \to \mu^+\mu^-$ provide an excellent test of the flavor sector of the Standard Model with sensitivity to many new physics models. We report on a search for these decays with the CMS experiment using $1.14\,\mathrm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s} = 7\,\mathrm{TeV}$ collected in the first half of 2011. The number of events observed after all selection requirements is consistent with the expectation from Standard Model sources. The resulting upper limits on the branching fractions are ${\cal B}(B^0_s \to \mu^+\mu^-) < 1.9\times10^{-8}$ and ${\cal B}(B^0 \to \mu^+\mu^-) < 4.6\times10^{-9}$, at 95\% confidence level.