Study of the q2 dependence of B→πlν and of B→ρ(ω)lν and extraction of |Vub| -: art. no. 072003

We report on determinations of \V-ub\ resulting from studies of the branching fraction and q(2) distributions in exclusive semileptonic B decays that proceed via the b-->u transition. Our data set consists of the 9.7x106B (B) over bar meson pairs collected at the Y(4S) resonance with the CLEO II detector. We measure B(B-0-->pi(-)l(+)nu)=(1.33+/-0.18+/-0.11+/-0.01+/-0.07)x10(-4) and B(B-0-->rho(-)l(+)nu)=(2.17+/-0.34(-0.54)(+0.47)+/-0.41+/-0.01)x10(-4), where the errors are statistical, experimental systematic, systematic due to residual form-factor uncertainties in the signal, and systematic due to residual form-factor uncertainties in the cross-feed modes, respectively. We also find B(B+-->etal(+)nu)=(0.84+/-0.31+/-0.16+/-0.09)x10(-4), consistent with what is expected from the B-->pilnu mode and quark model symmetries. We extract \V-ub\ using light-cone sum rules for 0less than or equal toq(2)<16 GeV2 and lattice QCD for 16 GeV(2)less than or equal toq(2)<q(max)(2). Combining both intervals yields \V-ub\=(3.24+/-0.22+/-0.13(-0.39)(+0.55)+/-0.09)x10(-3) for pilnu, and \V-ub\=(3.00+/-0.21(-0.35-0.38)(+0.29+0.49)+/-0.28)x10(-3) for rholnu, where the errors are statistical, experimental systematic, theoretical, and rholnu form-factor shape, respectively. Our combined value from both decay modes is \V-ub\=(3.17+/-0.17(-0.17-0.39)(+0.16+0.53)+/-0.03)x10(-3).