Observation ofB→K±π0andB→K0π0, and Evidence forB→π+π−

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: B(B{yields}{pi}{sup +}{pi}{sup -})=(4.3{sup +1.6}{sub -1.4}{+-}0.5)x10{sup -6} , B(B{yields}K{sup 0}{pi}{sup 0}) =(14.6{sup +5.9+2.4}{sub -5.1-3.3})x 10{sup -6} , and B(B{yields}K{sup {+-}}{pi}{sup 0} )=(11.6{sup +3.0+1.4}{sub -2.7-1.3}) x10{sup -6} . We also update our previous measurements for the decays B{yields}K{sup {+-}}{pi}{sup {+-}} and B{sup {+-}}{yields}K{sup 0}{pi}{sup {+-}} . (c) 2000 The American Physical Society.