Study of the rare decays of Bs0 and B0 into muon pairs from data collected during the LHC Run 1 with the ATLAS detector

A study of the decays Bs0→μ+μ- and B0→ μ+μ- has been performed using data corresponding to an integrated luminosity of 25 fb- 1 of 7 and 8 TeV proton–proton collisions collected with the ATLAS detector during the LHC Run 1. For the B0 dimuon decay, an upper limit on the branching fraction is set at B(B0→ μ+μ-) < 4.2 × 10 - 10 at 95 % confidence level. For Bs0, the branching fraction B(Bs0→μ+μ-)=(0.9-0.8+1.1)×10-9 is measured. The results are consistent with the Standard Model expectation with a p value of 4.8 %, corresponding to 2.0 standard deviations.