LHCb CollaborationCalefice, LukasComerma Montells, AlbertGarcia Moreno, PaulaGarrido Beltrán, LluísGioventù, AlessandraGironella Gironell, PereGomez Fernandez, SergioGraugés Pous, EugeniLaguarta Gonzalez, P.Lobo Salvia, AniolLópez Huertas, AlbertManera Escalero, RafelMarin Benito, CarlaMauricio Ferre, JoanAlfonso Albero, AlejandroVazquez Gomez, Ricardo2025-06-272025-06-2720241126-6708https://hdl.handle.net/2445/221842 A study of B+ c → χcπ + decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1 . The decay B+ c → χc2π + is observed for the frst time, with a signifcance exceeding seven standard deviations. The relative branching fraction with respect to the B+ c → J/ψπ+ decay is measured to be BB + c →χc2π+ BB + c →J/ψπ+ = 0.37 ± 0.06 ± 0.02 ± 0.01 , where the frst uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the χc2 → J/ψγ branching fraction. No signifcant B+ c → χc1π + signal is observed and an upper limit for the relative branching fraction for the B+ c → χc1π + and B+ c → χc2π + decays of BB + c →χc1π+ BB + c →χc2π+ < 0.49 is set at the 90% confdence level. 30 p.application/pdfengcc-by (c) Aaij, R. et al., 2024http://creativecommons.org/licenses/by/4.0/HadronsFísica de partículesHadronsParticle physicsinfo:eu-repo/semantics/article7564612025-06-27info:eu-repo/semantics/openAccess