Observation of the decay Λ b 0 → χ c1 pπ −

Abstract

Abstract: The Cabibbo-suppressed decay Λb0→ χc1pπ− is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6 fb−1, collected with the LHCb detector at a centre-of-mass energy of 13 TeV. Evidence for the Λb0→ χc2pπ− decay is also found. Using the Λb0→ χc1pK− decay as normalisation channel, the ratios of branching fractions are measured to beBΛb0→χc1pπ−BΛb0→χc1pK−=6.59±1.01±0.22×10−2, BΛb0→χc2pπ−BΛb0→χc1pπ−=0.95±0.30±0.04±0.04, BΛb0→χc2pK−BΛb0→χc1pK−=1.06±0.05±0.04±0.04, where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of χc1, 2→ J/ψγ decays.