New results on the search for $B^0_s\rightarrow μ^+μ^-$ from LHCb

A search for the rare decays $B^0_s\rightarrow μ^+μ^-$ and $B^0\rightarrow μ^+μ^-$ is performed with the LHCb experiment using 1.1\,fb$^{-1}$ of data collected at $\sqrt s=8$\,TeV$and 1.0\,fb$^{-1}$of data collected at$\sqrt s=7$\,TeV. An excess of$B^0_s\rightarrow μ^+μ^-$candidates with respect to the background expectations is observed with a statistical significance of 3.5 standard deviations. A branching fraction of${\cal BR}(B^0_s\rightarrow μ^+μ^-) =(3.2^{+1.5}_{-1.2}) \times 10^{-9}$is measured with an unbinned maximum likelihood fit. The measured branching fraction is in agreement with the expectation from the Standard Model. The observed number of$B^0\rightarrow μ^+μ^-$candidates is consistent with the background expectation and an upper limit on the branching fraction of${\cal BR}(B^0\rightarrow μ^+μ^-) < 9.4\times10^{-10}$ is obtained.

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