Study of the rare View the MathML sourceBs0 and B0B0 decays into the π+π−μ+μ−π+π−μ+μ− final state

A search for the rare decays B0 s → π +π −μ+μ− and B0 → π +π −μ+μ− is performed in a data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb detector in proton- proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0 s → π +π −μ+μ− and the first evidence of the decay B0 → π +π −μ+μ− are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(B0 s → π +π −μ+μ−) = (8.6 ± 1.5 (stat) ± 0.7 (syst) ± 0.7 (norm)) × 10−8 and B(B0 → π +π −μ+μ−) = (2.11 ± 0.51 (stat) ± 0.15 (syst) ± 0.16 (norm)) × 10−8, where the third uncertainty is due to the branching fraction of the decay B0 → J /ψ(→ μ+μ−)K ∗(892)0(→ K +π −), used as a normalisatio