Study of b -hadron decays to Λ ⁺_c h ⁻ h′ ⁻ final states

Decays of Ξ⁻_b and Ω⁻_b baryons to Λ⁺_ch⁻h′⁻ final states, with h⁻h′⁻ being π⁻π⁻, K⁻π⁻ and K⁻K⁻ meson pairs, are searched for using data collected with the LHCb detector. The data sample studied corresponds to an integrated luminosity of 8.7fb⁻¹ of pp collisions collected at centre-of-mass energies s√=7, 8 and 13TeV. The products of the relative branching fractions and fragmentation fractions for each signal mode, relative to the B⁻→Λ⁺_cp^-π⁻ mode, are measured, with Ξ⁻b→Λ⁺_cK⁻π⁻, Ξ⁻_b→Λ⁺_cK⁻K⁻ and Ω⁻_b→Λ⁺_cK⁻K⁻ decays being observed at over 5σ significance. The Ξ⁻_b→Λ⁺_cK⁻π⁻ mode is also used to measure the Ξ⁻_b production asymmetry, which is found to be consistent with zero. In addition, the B⁻→Λ⁺_cpK⁻ decay is observed for the first time, and its branching fraction is measured relative to that of the B⁻→Λ⁺_cp^-π⁻ mode.