Search for rare B(s)⁰→μ⁺μ ^-μ⁺μ^- decays

A search for the decays Bs ⁰→μ ⁺μ ^-μ ⁺μ ^- and B ⁰→μ ⁺μ ^-μ ⁺μ ^- is performed using data, corresponding to an integrated luminosity of 1.0 fb ^-1, collected with the LHCb detector in 2011. The number of candidates observed is consistent with the expected background and, assuming phase-space models of the decays, limits on the branching fractions are set: B(Bs ⁰→μ ⁺μ ^-μ ⁺μ ^-)<1.6(1.2) ×10 ^-8 and B(B ⁰→μ ⁺μ ^-μ ⁺μ ^-)<6.6(5.3)×10 ^-9 at 95% (90%) confidence level. In addition, limits are set in the context of a supersymmetric model which allows for the B(s) ⁰ meson to decay into a scalar (S) and pseudoscalar particle (P), where S and P have masses of 2.5 GeV/c and 214.3 MeV/c, respectively, both resonances decay into μ ⁺μ ^-. The branching fraction limits for these decays are B(Bs ⁰→SP)<1.6(1.2)×10 ^-8 and B(B ⁰→SP)<6.3(5.1)×10 ^-9 at 95% (90%) confidence level.