Observation of $B_{c}^{+} rightarrow D^{0} K^{+}$ decays

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV, the $B_{c}^{+} rightarrow D^{0} K^{+}$ decay is observed with a statistical significance of 5.1 standard deviations. By normalising to $B^{+} rightarrow bar{D}^{0} pi^{+}$ decays, a measurement of the branching fraction multiplied by the production rates for $B_{c}^{+}$ relative to $B^{+}$ mesons in the LHCb acceptance is obtained, $$ R_{D^{0} K} = frac{f_{c}}{f_{u}}timesmathcal{B}(B_{c}^{+} rightarrow D^{0} K^{+}) = (9.3,^{+2.8}_{-2.5} pm 0.6) times 10^{-7},, $$ where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first $B_{c}^{+}$ decay of this nature to be observed.