Observation of the rare $B_s^0\to {\mu }^{+}{\mu }^{-}$ decay from the combined analysis of CMS and LHCb data

Abstract

A joint measurement is presented of the branching fractions $B_s^0\to {\mu }^{+}{\mu }^{-}$ and $B^0\to {\mu }^{+}{\mu }^{-}$ in proton-proton collisions at the LHC by the CMS and LHCb experiments. The data samples were collected in 2011 at a centre-of-mass energy of 7 TeV, and in 2012 at 8 TeV. The combined analysis produces the first observation of the $B_s^0\to {\mu }^{+}{\mu }^{-}$ decay, with a statistical significance exceeding six standard deviations, and the best measurement of its branching fraction so far. Furthermore, evidence for the $B^0\to {\mu }^{+}{\mu }^{-}$ decay is obtained with a statistical significance of three standard deviations. The branching fraction measurements are statistically compatible with SM predictions and impose stringent constraints on several theories beyond the SM.

Comments: Correspondence should be addressed to cms-and-lhcb-publication-committees@cern.ch