First Observation of a Baryonic B+c Decay

Abstract

A baryonic decay of the B + c meson, B + c → J / ψ p ¯ p π + , is observed for the first time, with a significance of 7.3 standard deviations, in p p collision data collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb − 1 taken at center-of-mass energies of 7 and 8 TeV. With the B + c → J / ψ π + decay as the normalization channel, the ratio of branching fractions is measured to be B ( B + c → J / ψ p ¯ p π + ) / B ( B + c → J / ψ π + ) = 0.14 3 + 0.039 − 0.034 ( stat ) ± 0.013 ( syst ) . The mass of the B + c meson is determined as M ( B + c ) = 6274.0 ± 1.8 ( stat ) ± 0.4 ( syst ) MeV / c 2 , using the B + c → J / ψ p ¯ p π + channel.