Measurement of the $B^0_s\to\mu^+\mu^-$ decay properties and search for the $B^0\to\mu^+\mu^-$ and $B^0_s\to\mu^+\mu^-\gamma$ decays

International audienceAn improved measurement of the decay Bs0→μ+μ- and searches for the decays B0→μ+μ- and Bs0→μ+μ-γ are performed at the LHCb experiment using data collected in proton-proton collisions at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2 and 6 fb-1, respectively. The Bs0→μ+μ- branching fraction and effective lifetime are measured to be B(Bs0→μ+μ-)=(3.09-0.43-0.11+0.46+0.15)×10-9 and τ(Bs0→μ+μ-)=(2.07±0.29±0.03) ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for B0→μ+μ- and Bs0→μ+μ-γ decays is found and the upper limits B(B0→μ+μ-)<2.6×10-10 and B(Bs0→μ+μ-γ)<2.0×10-9 at 95% confidence level are determined, where the latter is limited to the range mμμ>4.9 GeV/c2. Additionally, the ratio between the B0→μ+μ- and Bs0→μ+μ- branching fractions is measured to be Rμ+μ-<0.095 at 95% confidence level. The results are in agreement with the Standard Model predictions