UC Irvine

A study of the decays Bs0→μ+μ-$$B^0_s \rightarrow \mu ^+\mu ^-$$ and B0→μ+μ-$$B^0 \rightarrow \mu ^+\mu ^-$$ has been performed using data corresponding to an integrated luminosity of 25 fb-1$$^{-1}$$ of 7 and 8 TeV proton–proton collisions collected with the ATLAS detector during the LHC Run 1. For the B0$$B^0$$ dimuon decay, an upper limit on the branching fraction is set at B(B0→μ+μ-)<4.2×10-10$$\mathcal{B}(B^0 \rightarrow \mu ^+\mu ^-) < 4.2 \times 10^{-10}$$ at 95 % confidence level. For Bs0$$B^0_s$$, the branching fraction B(Bs0→μ+μ-)=0.9-0.8+1.1×10-9$$\mathcal{B}(B^0_s \rightarrow \mu ^+\mu ^-) = \left( 0.9^{+1.1}_{-0.8} \right) \times 10^{-9}$$ is measured. The results are consistent with the Standard Model expectation with a p value of 4.8 %, corresponding to 2.0 standard deviations.