First measurement of the B->pi l nu and B->rho(omega)l nu branching fractions

Abstract

CLEO has studied B decays to pi l nu, rho l nu, and omega l nu, where l = e or mu, by incorporating the missing momentum into full B reconstruction. With the B-0 and B+ modes combined according to isospin predictions for the relative partial widths, we obtain B(B-0 --> pi(-)l(+)nu) = (1.8 +/- 0.4 +/- 0.3 +/- 0.2) x 10(-4) and B(B-0 --> rho(-)l(+)nu) = (2.5 +/- 0.4(0.7)(+0.5) +/- 0.5) x 10(-4), where the errors are statistical, systematic, and the estimated model dependence. We also estimate \V-ub\ = (3.3 +/- 0.2(-0.4)(+0.3) +/- 0.7) x 10(-3).