Search for the Λb⁰ →Λη ′ and Λb⁰ → Λη decays with the LHCb detector

A search is performed for the as yet unobserved baryonic Λ _b ⁰ → Λη ′ and Λ _b ⁰ → Λη decays with 3 fb ⁻¹ of proton-proton collision data recorded by the LHCb experiment. The B ⁰ → K _s ⁰η ′ decay is used as a normalisation channel. No significant signal is observed for the Λ _b ⁰ → Λη ′ decay. An upper limit is found on the branching fraction of ℬΛb0→Λη′ < 3.1 × 10 ⁻⁶ at 90% confidence level. Evidence is seen for the presence of the Λ _b ⁰ → Λη decay at the level of 3σ significance, with a branching fraction (Formula presented.).