Observation of the Λ0b → J/ψ Ξ− K+ and Ξ0b → J/ψ Ξ− π+ decays

The first observation of the Ξ0b → J/ψ Ξ− π+ decay and the most precise measurement of the branching fraction of the Λ0b → J/ψ Ξ− K+ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016-2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb^−1. Using the Λ0b → J/ψ Λ and Ξ0b → J/ψ Ξ− decays as normalisation channels, the ratios of branching fractions are measured to be: BR(Λ0b → J/ψ Ξ− K+)/BR(Λ0b → J/ψ Λ) = (1.17 ± 0.14 ± 0.08) × 10^−2, BR(Ξ0b → J/ψ Ξ− π+)/BR(Ξ0b → J/ψ Ξ−) = (11.9 ± 1.4 ± 0.6) × 10^−2, where the first uncertainty is statistical and the second systematic.