Searches for Λ0bΛb0 and Ξ0bΞb0 decays to K0Spπ−KS0pπ− and K0SpK−KS0pK−final states with first observation of the Λ0b→K0Spπ−Λb0→KS0pπ−decay

A search for previously unobserved decays of beauty baryons to the final states K0Spπ−KS0pπ− and K0SpK−KS0pK− is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb⁻¹ of pp collisions. The Λ0b→K¯¯¯¯¯0pπ−Λb0→K¯0pπ− decay is observed with a significance of 8.6 σ, with branching fractionB(Λ0b→K¯¯¯¯¯0pπ−)=(1.26±0.19±0.09±0.34±0.05)×10−5,B(Λb0→K¯0pπ−)=(1.26±0.19±0.09±0.34±0.05)×10−5,where the uncertainties are statistical, systematic, from the ratio of fragmentation fractions fΛ0b/fd,fΛb0/fd, and from the branching fraction of the B⁰ → K⁰π⁺π⁻ normalisation channel, respectively. A first measurement is made of the CP asymmetry, givingACP(Λ0b→K¯¯¯¯¯0pπ−)=0.22±0.13(stat)±0.03(syst).ACP(Λb0→K¯0pπ−)=0.22±0.13(stat)±0.03(syst).No significant signals are seen for Λ0b→K0SpK−Λb0→KS0pK− decays, Ξ0bΞb0 decays to both the K0Spπ−KS0pπ− and K0SpK−KS0pK− final states, and the Λ0b→D−s(→K0SK−)pΛb0→Ds−(→KS0K−)p decay, and upper limits on their branching fractions are reported.