Observation of B(0) decay to 2 charmless mesons

Abstract

We report results from a search for the decays B0 --> pi+pi-, B0 --> K+pi-, and B0 --> K+K-. We find 90% confidence level upper limits on the branching fractions, B(pipi) < 2.9 x 10(-5) , B(Kpi) < 2.6 x 10(-5), and B(KK) < 0.7 x 10(-5). While there is no statistically significant signal in the individual modes, the sum of B(pipi) and B(Kpi) exceeds zero with a significance of more than 4 standard deviations, indicating that we have observed charmless hadronic B decays.