Observation of the Λ b 0 → J / ψ Ξ - K + and Ξ b 0 → J / ψ Ξ - π + decays

Abstract

The first observation of the Ξ b 0 → J / ψ Ξ - π + decay and the most precise measurement of the branching fraction of the Λ b 0 → J / ψ Ξ - K + decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre-of-mass energy of 13 \,Te V , corresponding to an integrated luminosity of 5.4 \,fb - 1 . Using the Λ b 0 → J / ψ Λ and Ξ b - → J / ψ Ξ - decays as normalisation channels, the ratios of branching fractions are measured to be B ( Λ b 0 → J / ψ Ξ - K + ) B ( Λ b 0 → J / ψ Λ ) = ( 1.17 ± 0.14 ± 0.08 ) × 10 - 2 , B ( Ξ b 0 → J / ψ Ξ - π + ) B ( Ξ b - → J / ψ Ξ - ) = ( 11.9 ± 1.4 ± 0.6 ) × 10 - 2 , where the first uncertainty is statistical and the second systematic.