B Decays to Two Charmless Pseudoscalar Mesons at CLEO

Using 3.3 Million $B\bar B$ pairs accumulated with the CLEO detector CLEO has measured ${\cal B}(B^0\to K^+\pi^-) = (1.5^{+ 0.5}_{-0.4}\pm 0.1\pm 0.1)\times 10^{-5}$, ${\cal B}(B^+\to K^0\pi^+) = (2.3^{+1.1}_{-1.0}\pm 0.2\pm 0.2)\times 10^{-5}$, and ${\cal B}(B^+\to \eta^{'}K^+) = (7.8^{+ 2.7}_{-2.2}\pm 1.0)\times 10^{-5}$. These constitute the first observations of exclusive $B$\ decays to charmless hadronic final states. Furthermore, a measurement of ${\cal B}(B^+\to h^+\pi^0) = (1.6^{+ 0.6 +0.3}_{-0.5 -0.2}\pm 0.1)\times 10^{-5}$, as well as upper limits on various other $B$ decays to two charmless pseudoscalar mesons are presented. In particular, an upper limit of ${\cal B}(B^0\to \pi^+\pi^-) < 1.5\times 10^{-5}$ @ 90%C.L. is placed. All of these results are still preliminary, and averaging over charge conjugate modes is always implied.