  We have studied two-body charmless hadronic decays of B mesons into the final
states $\pi\pi$, $K \pi$, and $KK$. Using 3.3 million $B\bar{B}$ pairs
collected with the CLEO-II detector, we have made the first observation of the
decays $B^0\to K^+\pi^-$, $B^+\to K^0\pi^+$, and the sum of $B^+ \to
\pi^+\pi^0$ and $B^+ \to K^+\pi^0$ decays (an average over charge-conjugate
states is always implied). We place upper limits on branching fractions for the
remaining decay modes.

High Energy Physics - Experiment