New results on the search for $B_s^0\to {\mu }^{+}{\mu }^{-}$ from LHCb

Abstract

A search for the rare decays $B_s^0\to {\mu }^{+}{\mu }^{-}$ and $B^0\to {\mu }^{+}{\mu }^{-}$ is performed with the LHCb experiment using 1.1\,fb${}^{-1}$ of data collected at $\sqrt{s}=8$\,TeV$and1.0fb$^{-1}$ofdatacollectedat$\sqrt s=7$TeV.Anexcessof$B^0_s\rightarrow \mu^+\mu^-$candidateswithrespecttothebackgroundexpectationsisobservedwithastatisticalsignificanceof3.5standarddeviations.Abranchingfractionof${\cal BR}(B^0_s\rightarrow \mu^+\mu^-) =(3.2^{+1.5}_{-1.2}) \times 10^{-9}$ismeasuredwithanunbinnedmaximumlikelihoodfit.ThemeasuredbranchingfractionisinagreementwiththeexpectationfromtheStandardModel.Theobservednumberof$B^0\rightarrow \mu^+\mu^-$candidatesisconsistentwiththebackgroundexpectationandanupperlimitonthebranchingfractionof${\cal BR}(B^0\rightarrow \mu^+\mu^-) < 9.4\times10^{-10}$ is obtained.

Comments: Proceedings for the HCP2012 conference