Evidence for B^+ -> omega l^+ nu

Abstract

We have searched for the decay B^+ -> omega l^+ nu in 78 fb^-1 of Y(4S) data (85.0 million BBbar events) accumulated with the Belle detector. The final state is fully reconstructed using the omega decay into pi^+ pi^- pi^0 and detector hermeticity to estimate the neutrino momentum. 155 +/- 47 signal events are found in the data, corresponding to a branching fraction of (1.3 +/- 0.4 +/- 0.2 +/- 0.3) x 10^-4, where the first two errors are statistical and systematic. The third error is due to the estimated form-factor uncertainty. (This result is preliminary.)