Searches for Λ0 b and Ξ0 b decays to K0 S pπ− and K0 S pK− final states with first observation of the Λ0 b → K0 S pπ− decay

摘要

A search for previously unobserved decays of beauty baryons to the final states K0 spπ- 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 Λ0 b → ̄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 Λ 0 b/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 Λ0 b → K0 spK - decays, Ξ0 b decays to both the K 0 spπ- and K0 spK - final states, and the Λ0 b → D- s(→ K0 sK-)p decay, and upper limits on their branching fractions are reported.