Searches for Λ⁰_b and Ξ⁰_b decays to K⁰_spπ and K⁰_spK^- final states with first observation of the Λ⁰_b → K⁰_spπ ^- decay

A search for previously unobserved decays of beauty baryons to the final states K0spπ- and K0 spK- is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb- of pp collisions. The Λ0b → ̄K pπ- decay is observed with a significance of 8.6σ, with branching fraction (Equation Presented), where the uncertainties are statistical, systematic, from the ratio of fragmentation fractions f Λ0b/fd, and from the branching fraction of the B0 → K0π+π - normalisation channel, respectively. A first measurement is made of the CP asymmetry, giving (Equation Presented). No significant signals are seen for Λ0b → K0spK - decays, Ξ0b decays to both the K 0spπ- and K0spK - final states, and the Λ0b → D-s(→ K0sK-)p decay, and upper limits on their branching fractions are reported.