TY - JOUR AU - LHCb Collaboration (Aaij, R. et al AU - Henry, L. AU - Jashal, B. K. AU - Martinez-Vidal, F. AU - Oyanguren, A. AU - Remon Alepuz, C. AU - Ruiz Vidal, J. PY - 2021 DA - 2021// TI - Observation of the decay Lambda b0 -> chi(c1)p pi(-) T2 - J. High Energy Phys. JO - Journal of High Energy Physics SP - 095 EP - 21pp VL - 05 IS - 5 PB - Springer KW - B physics KW - Branching fraction KW - Hadron-Hadron scattering (experiments) KW - QCD KW - Quarkonium AB - The Cabibbo-suppressed decay Lambda b0-> chi (c1)p(-) 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 Lambda b0-> chi (c2)p(-) decay is also found. Using the Lambda b0-> chi (c1)pK(-) decay as normalisation channel, the ratios of branching fractions are measured to beBLambda b0-> chi c1p pi-BLambda b0-> chi c1pK-=6.59 +/- 1.01 +/- 0.22x10-2,BLambda b0 -> chi c2p pi-BLambda b0 -> chi c1p pi-=0.95 +/- 0.30 +/- 0.04 +/- 0.04,BLambda b0 -> chi c2pK-BLambda b0 -> chi c1pK-=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 chi (c1,2)-> J/psi gamma decays.