Measurement of the $B_s^0\to {\mu }^{+}{\mu }^{-}$ branching fraction and search for $B^0\to {\mu }^{+}{\mu }^{-}$ decays at the LHCb experiment

Abstract

A search for the rare decays $B_s^0\to {\mu }^{+}{\mu }^{-}$ and $B^0\to {\mu }^{+}{\mu }^{-}$ is performed at the LHCb experiment. The data analysed correspond to an integrated luminosity of 1 fb${}^{-1}$ of $pp$ collisions at a centre-of-mass energy of 7 TeV and 2 fb${}^{-1}$ at 8 TeV. An excess of $B_s^0\to {\mu }^{+}{\mu }^{-}$ signal candidates with respect to the background expectation is seen with a significance of 4.0 standard deviations. A time-integrated branching fraction of $\mathcal{B}(B_s^0\to {\mu }^{+}{\mu }^{-})=(2.9_{-1.0}^{+1.1})\times 10^{-9}$ is obtained and an upper limit of $\mathcal{B}(B^0\to {\mu }^{+}{\mu }^{-})<7.4\times 10^{-10}$ at 95% confidence level is set. These results are consistent with the Standard Model expectations.

Comments: 12 pages, 3 figures, Phys. Rev. Lett. 111, 101805 (2013)