Observation of Ξb0→Ξc+Ds- and Ξb-→Ξc0Ds- decays.

The Ξ b 0 → Ξ c + D s - and Ξ b - → Ξ c 0 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 Λ b 0 baryon are measured to be R Ξ b 0 Λ b 0 ≡ σ Ξ b 0 σ Λ b 0 × B Ξ b 0 → Ξ c + D s - B Λ b 0 → Λ c 0 D s - = (15.8 ± 1.1 ± 0.6 ± 7.7) % , R Ξ b - Λ b 0 ≡ σ Ξ b - σ Λ b 0 × B Ξ b - → Ξ c 0 D s - B Λ b 0 → Λ c 0 D s - = (16.9 ± 1.3 ± 0.9 ± 4.3) % , where 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 Ξ b 0 and Ξ b - baryons are measured to be m Ξ b 0 = 5791.12 ± 0.60 ± 0.45 ± 0.24 MeV / c 2 and m Ξ b - = 5797.02 ± 0.63 ± 0.49 ± 0.29 MeV / c 2 , where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively. [ABSTRACT FROM AUTHOR]