Observation of ᴧ _b ⁰→ ᴧ _c ⁺ D̄ ^(*)0K ⁻ and ᴧ _b ⁰→ ᴧ _c ⁺ D _s ^*− decays

The decays Λ_b⁰→Λ_c⁺D¯^(∗)0K^- and Λ_b⁰→Λ_c⁺D_s^∗- are observed for the first time, in proton-proton collision data at s=13TeV, corresponding to an integrated luminosity of 5.4fb^-1 collected with the LHCb detector. Their ratios of branching fractions with respect to the Λ_b⁰→Λ_c⁺D_s^- mode are measured to be (Formula presented.) where the first uncertainties are statistical, the second systematic, and the third, for the Λ_b⁰→Λ_c⁺D¯^(∗)0K^- decays, are due to the uncertainties on the branching fractions of the D_s^-→K^-K⁺π^- and D¯⁰→K⁺π^- decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in Λ_b⁰→Λ_c⁺D¯^(∗)0K^- decay channels.