Measurement of branching fractions of charmless four-body Λ_b ⁰ and Ξ_b ⁰ decays

A search for charmless four-body decays of Λ_b ⁰ and Ξ_b ⁰ baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in 2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb⁻¹. Six decay modes are observed, among which Λ_b ⁰ → pK⁻π⁺π⁻,Λ_b ⁰ → pK⁻K⁺K⁻,Ξ_b ⁰ → pK⁻π⁺π⁻ and Ξ_b ⁰ → pK⁻π⁺K⁻ are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the Ξ_b ⁰ baryon) are determined relative to the Λ_b ⁰ → Λ_c ⁺π⁻ decay.[Figure not available: see fulltext.].