Observation of Ξ0b → Ξ+c D−s and Ξ−b → Ξ0c D−s decays

The Ξ⁰_b → Ξ⁺_c D⁻_s and Ξ⁻_b → Ξ⁰_c D⁻_s decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of √s = 13 TeV, corresponding to an integrated luminosity of 5.1 fb⁻¹. The branching fractions times the production cross-sections of Ξ_b baryons relative to that of Λ⁰_b baryon are measured to be: R(Ξ⁰_b / Λ⁰_b) = (15.8 ± 1.1 ± 0.6 ± 7.7)% R(Ξ⁻_b / Λ⁰_b) = (16.9 ± 1.3 ± 0.9 ± 4.3)% The first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the decay branching fractions of relevant charmed baryons. The masses of Ξ⁰_b and Ξ⁻_b baryons are measured to be: m(Ξ⁰_b) = 5791.12 ± 0.60 ± 0.45 ± 0.24 MeV/c² m(Ξ⁻_b) = 5797.02 ± 0.63 ± 0.49 ± 0.29 MeV/c² where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively.