Observation of the Λ⁰_b→J/ψΛϕ decay in proton-proton collisions at √s = 13 TeV

The observation of the Λ⁰_b→J/ψΛϕ decay is reported using proton-proton collision data collected at √s = 13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60fb⁻¹. The ratio of the branching fractions B(Λ⁰_b →J/ψΛϕ)/B(Λ⁰_b →ψ(2S)Λ) is measured to be (8.26±0.90(stat) ±0.68(syst)±0.11(B))×10⁻², where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of ϕ and ψ(2S) decays to the reconstructed final states.