Observation of the Λb0 ⁣→J ⁣/ψΞ−K+ and Ξb0 ⁣→J ⁣/ψΞ−π+decays

The first observation of the Ξ 0b → J/ψΞ −π+decay and the most precise measurement of the branching fraction of the Λ0b → J/ψΞ − 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/ψΛ and Ξ −b → J/ψΞ − decays as normalisation channels, the ratios of branching fractions are measured to be B(Λ0b → J/ψΞ − K +)B(Λ0b → J/ψΛ) = (1.17 ± 0.14 ± 0.08) × 10−2 , B(Ξ 0b → J/ψΞ −π+)B(Ξ −b → J/ψΞ −) = (11.9 ± 1.4 ± 0.6) × 10−2 , where the first uncertainty is statistical and the second systematic.