Observation of ⁰b \!→ ⁺c 1.79993pt-1.79993ptD (*)0K ⁻ and ⁰b \!→ ⁺c D *-ₛ decays

The decays ⁰b \!→ ⁺c 1.79993pt-1.79993ptD (*)0K ⁻ Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - and ⁰b \!→ ⁺c D *-ₛ Λ b 0 → Λ c + D s ∗ - are observed for the first time, in proton-proton collision data at √s =13 Te-1.00006ptV s = 13 Te V , corresponding to an integrated luminosity of 5.4 fb ⁻¹ fb - 1 collected with the LHCb detector. Their ratios of branching fractions with respect to the ⁰b \!→ ⁺c D ⁻ₛ Λ b 0 → Λ c + D s - mode are measured to be $${aligned} {aligned} {B( {{ } ^0b} \!→ {{ } ^+c} {{{1.79993pt}{{-1.79993pt}D}} {}^0} {{K} ^-} ) }{B( {{ } ^0b} \!→ {{ } ^+c} {{D} ^-ₛ} ) }&= 0.1908 {}-0.0034+0.0036 {}-0.0018+0.0016 ± 0.0038,\\ {B( {{ } ^0b} \!→ {{ } ^+c} {{{1.79993pt}{{-1.79993pt}D}} {}*0} {{K} ^-} ) }{B( {{ } ^0b} \!→ {{ } ^+c} {{D} ^-ₛ} ) }&= 0.589 {}-0.017+0.018 {}-0.018+0.017 ± 0.012,\\ {B( {{ } ^0b} \!→ {{ } ^+c} {{D} *-ₛ} ) }{B( {{ } ^0b} \!→ {{ } ^+c} {{D} ^-ₛ} ) }&= 1.668 ± 0.022 {}-0.055+0.061, {aligned} {aligned}$$ B Λ b 0 → Λ c + D ¯ 0 K - B Λ b 0 → Λ c + D s - = 0.1908 - 0.0034 + 0.0036 - 0.0018 + 0.0016 ± 0.0038 , B Λ b 0 → Λ c + D ¯ ∗ 0 K - B Λ b 0 → Λ c + D s - = 0.589 - 0.017 + 0.018 - 0.018 + 0.017 ± 0.012 , B Λ b 0 → Λ c + D s ∗ - B Λ b 0 → Λ c + D s - = 1.668 ± 0.022 - 0.055 + 0.061 , where the first uncertainties are statistical, the second systematic, and the third, for the ⁰b \!→ ⁺c 1.79993pt-1.79993ptD (*)0K ⁻ Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - decays, are due to the uncertainties on the branching fractions of the D ⁻ₛ \!→ K ⁻ K ⁺ π ⁻ D s - → K - K + π - and 1.79993pt-1.79993ptD ⁰ \!→ K ⁺ π ⁻ 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 ⁰b \!→ ⁺c 1.79993pt-1.79993ptD (*)0K ⁻ Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - decay channels.