Study of B+ c → χcπ + decays

Abstract

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.