Observation of $B_c^{+}\to J/\ddot{I}ˆD_s^{+}$ and $B_c^{+}\to J/\ddot{I}ˆD_s^{\ast +}$ decays

Abstract

The decays $B_c^{+}\to J/\ddot{I}ˆD_s^{+}$ and $B_c^{+}\to J/\ddot{I}ˆD_s^{\ast +}$ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3$f{b}^{-1}$, collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$=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 $BR(B_c^{+}\to J/\ddot{I}ˆD_s^{+})/BR(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}€+)=2.90\pm 0.57\pm 0.24$, $BR(B_c^{+}\to J/\ddot{I}ˆD_s^{\ast +})/BR(B_c^{+}\to J/\ddot{I}ˆD_s^{+})=2.37\pm 0.56\pm 0.10$, where the first uncertainties are statistical and the second systematic. The mass of the \Bc meson is measured to be $m_{B_c^{+}}=6276.28\pm 1.44(stat)\pm 0.36(syst)MeV/c^2$, using the $B_c^{+}\to J/\ddot{I}ˆD_s^{+}$ decay mode.

20 pages, 4 figures