Study of Two-Body B Decays to Kaons and Pions: Observation of B->pi+pi-, B-> K+-pi0, and B-> K0pi0 Decays

We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions and observe three new processes with the following branching fractions: BR(B-> pi+ pi-) = (4.3^{+1.6}_{-1.4} \pm 0.5) \times 10^{-6}, BR(B-> K0 pi0) = (14.6^{+5.9+2.4}_{-5.1-3.3}) \times 10^{-6}, and BR(B-> K+- pi0) = (11.6^{+3.0+1.4}_{-2.7-1.3}) \times 10^{-6}. We also update our previous measurements for the decays B->K+- pi-+ and B-> K0 pi+-.