Measurement of the differential branching fraction of the decay Λb0→Λμ+μ-

Abstract

The differential branching fraction of the decay Λ0 b → Λμ+μ− is measured as a function of the square of the dimuon invariant mass, q2. A yield of 78 ± 12 Λ0 b → Λμ+μ− decays is observed using data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. A significant signal is found in the q2 region above the square of the J /ψ mass, while at lower-q2 values upper limits are set on the differential branching fraction. Integrating the differential branching fraction over q2, while excluding the J /ψ and ψ(2S) regions, gives a branching fraction of B(Λ0 b → Λμ+μ−) = (0.96 ± 0.16(stat) ± 0.13(syst) ± 0.21(norm)) × 10−6, where the uncertainties are statistical, systematic and due to the normalisation mode, Λ0 b → J /ψΛ, respectively.