Observation of the decay Λ_b ⁰→Λ_c ⁺pp‾π⁻

The decay Λ_b ⁰→Λ_c ⁺pp‾π⁻ is observed using pp collision data collected with the LHCb detector at centre-of-mass energies of s=7 and 8 Tev, corresponding to an integrated luminosity of 3 fb⁻¹. The ratio of branching fractions between Λ_b ⁰→Λ_c ⁺pp‾π⁻ and Λ_b ⁰→Λ_c ⁺π⁻ decays is measured to be [Formula presented]=0.0540±0.0023±0.0032. Two resonant structures are observed in the Λ_c ⁺π⁻ mass spectrum of the Λ_b ⁰→Λ_c ⁺pp‾π⁻ decays, corresponding to the Σ_c(2455)⁰ and Σ_c ^⁎(2520)⁰ states. The ratios of branching fractions with respect to the decay Λ_b ⁰→Λ_c ⁺pp‾π⁻ are [Formula presented]=0.089±0.015±0.006,[Formula presented]=0.119±0.020±0.014. In all of the above results, the first uncertainty is statistical and the second is systematic. The phase space is also examined for the presence of dibaryon resonances. No evidence for such resonances is found.