Observation of B+→b+1K0 and search for B-meson decays to b01K0 and b1π0

We present the results of searches for decays of B mesons to final states with a b 1 meson and a neutral pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 × 10 6 B ¯¯¯ B pairs produced in e + e − annihilation. The results for the branching fractions are, in units of 10 − 6 , B ( B + → b + 1 K 0 ) = 9.6 ± 1.7 ± 0.9 , B ( B 0 → b 0 1 K 0 ) = 5.1 ± 1.8 ± 0.5 ( < 7.8 ), B ( B + → b + 1 π 0 ) = 1.8 ± 0.9 ± 0.2 ( < 3.3 ), and B ( B 0 → b 0 1 π 0 ) = 0.4 ± 0.8 ± 0.2 ( < 1.9 ), with the assumption that B ( b 1 → ω π ) = 1 . We also measure the charge asymmetry A ch ( B + → b + 1 K 0 ) = − 0.03 ± 0.15 ± 0.02 . The first error quoted is statistical, the second systematic, and the upper limits in parentheses indicate the 90% confidence level.