Observation of charmless hadronic B decays

Four candidates for charmless hadronic B decay are observed in a data sample of four million hadronic Z decays recorded by the aleph detector at lep. The probability that these events come from background sources is estimated to be less than 10−6. The average branching ratio of weakly decaying B hadrons (a mixture of Bd0, Bs0 and Λb weighted by their production cross sections and lifetimes, here denoted B) into two long-lived charged hadrons (pions, kaons or protons) is measured to be Br(B → h+h−) = (1.7−0.7+1.0 ± 0.2) × 10−5. The relative branching fraction Br(Bd(s)0 → π+π−(K−))Br(Bd(s)0 → h+h−) is measured to be 1.0−0.3 −0.1+0.0 +0.0. In addition, branching ratio upper limits are obtained for a variety of exclusive charmless hadronic two-body decays of B hadrons.