Studies of rare beauty and charm decays with the CMS experiment

Rare beauty meson decays $\mathrm{B}_\mathrm{s}^0\to\mu^+\mu^-$, $\mathrm{B^0}\to\mu^+\mu^-$, and charm meson decays $\mathrm{D^0}\to\mu^+\mu^-$ are searched in pp collisions at $\sqrt{s}=7\,\mathrm{TeV}$. A data sample corresponding to an integrated luminosity of $5\,\mathrm{fb}^{-1}$ collected by the CMS experiment is used for the $\mathrm{B}\to\mu^+\mu^-$ study, while the data sample used for $\mathrm{D^0}\to\mu^+\mu^-$ search is $90\,\mathrm{pb}^{-1}$. The number of events observed after applying the full selection criteria is consistent with the expectations from the sum of background and standard model signal. The resulting upper limits on the branching fractions are ${\cal B}(\mathrm{B}_\mathrm{s}^0\to\mu^+\mu^-) < 7.7\times10^{-9}$, ${\cal B}(\mathrm{B^0}\to\mu^+\mu^-) < 1.8\times10^{-9}$ at 95\% confidence level, and ${\cal B}(\mathrm{D^0}\to\mu^+\mu^-) < 5.4\times10^{-7}$ at 90\% confidence level.