First Observation of the Cabibbo Suppressed Decay $B^{+}\to \bar{D}^{0}K^{+}$

Abstract

We have observed the decay of the $B^-$ meson into $D^0 K^-$, using 3.3 million $B\bar B$ pairs collected with the CLEO II detector at the Cornell Electron Storage Ring. We find the branching fractions of this decay to be suppressed relative to the decay into $D^0 \pi^-$ by $0.055 \pm 0.014 \pm 0.005$.