Observation of B+c → J/ Ds+ and B+c → J/ Ds*+ decays

Abstract

The decays B+c → J/ Ds+ and B+c → J/ Ds*+ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3fb-1, collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of s=7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be BR(B+c → J/ Ds+)/BR(B+c → J/ π+) = 2.90 0.57 0.24, BR(B+c → J/ Ds*+) / BR (B+c → J/ Ds+) = 2.37 0.56 0.10, where the first uncertainties are statistical and the second systematic. The mass of the meson is measured to be mB+c = 6276.28 1.44 (stat) 0.36(syst) MeV/c2, using the B+c → J/ Ds+ decay mode.