Study of charmless hadronic B decays into the final states $K\pi ,\pi \pi$, and KK, with the first observation of $B\to {\pi }^{+}{\pi }^{-}$ and $B\to K^0{\pi }^0$

Abstract

We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions. We present preliminary results based on 9.66 million $B\bar{B}$ pairs collected with the CLEO detector. We have made the first observation of the decay $B\to {\pi }^{+}{\pi }^{-}$, with the branching fraction of $Br(B\to {\pi }^{+}{\pi }^{-})=(4.7_{-1.5}^{+1.8}\pm 0.6)\times 10^{-6}$. We have also observed for the first time the decay $B\to K^0{\pi }^0$ with the branching fraction of $Br(B\to K^0{\pi }^0)=(14.8_{-5.1-3.3}^{+5.9+2.4})\times 10^{-6}$, thus completing the set of four $K\pi$ branching fraction measurements. We present improved measurements for the decays $B\to K^{\pm }{\pi }^{\mp }$, $B^{\pm }\to K^0{\pi }^{\pm }$, and $B^{\pm }\to K^{\pm }{\pi }^0$. We use these and other charmless hadronic B decays to make a first determination of the value of the weak phase $\mathrm{Arg}(V_{ub}^{\ast })=\gamma ={113^{\circ }}_{-23^{\circ }}^{+25^{\circ }}$.

arXiv commentLeppho99 conference submission. All results are preliminary