Observation of $B^+_c \rightarrow J/\psi D_s^+$ and $B^+_c \rightarrow J/\psi D_s^{*+}$ decays

The decays $B^+_c \rightarrow J/\psi D_s^+$ and $B^+_c \rightarrow J/\psi D_s^{*+}$ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3$fb^{-1}$, 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 \begin{equation*}BR( B^+_c \rightarrow J/\psi D_s^+)/BR( B^+_c \rightarrow J/\psi \pi+ ) = 2.90 \pm 0.57 \pm 0.24$,\end{equation*} \begin{equation*}BR( B^+_c \rightarrow J/\psi D_s^{*+} ) / BR ( B^+_c \rightarrow J/\psi D_s^+ ) = 2.37 \pm 0.56 \pm 0.10, \end{equation*} where the first uncertainties are statistical and the second systematic. The mass of the $B^+_c$ meson is measured to be \begin{equation*}m_{B^+_c} = 6276.28 \pm 1.44 (stat) \pm 0.36(syst) MeV/c^2,\end{equation*} using the $B^+_c \rightarrow J/\psi D_s^+$ decay mode.