Study of exclusive charmless semileptonic B decays and extraction of |Vub| at CLEO

We have studied semileptonic B decay to the exclusive charmless states pi, rho/omega, eta and eta(') using the full 15.5 fb(-1) CLEO Upsilon(4S) sample, with measurements performed in subregions of phase space to minimize dependence on a priori knowledge of the form factors involved. We find total branching fractions B(B-0 ->pi(-)l(+)nu)=(1.37 +/- 0.15(stat)+/- 0.11(sys))x10(-4) and B(B-0 ->rho(-l+)nu)=(2.93 +/- 0.37(stat)+/- 0.37(sys))x10(-4). We find evidence for B+->eta('l+)nu, with B(B+->eta('l+)nu)=(2.66 +/-+/- 0.80(stat)+/- 0.56(sys))x10(-4) and 1.20x10(-4)< B(B+->eta('l+)nu)< 4.46x10(-4) (90% CL). We also limit B(B+->eta(l+)nu)< 1.01x10(-4) (90% CL). By combining our B ->pi l nu information with unquenched lattice calculations, we find |V-ub|=(3.6 +/- 0.4(stat)+/- 0.2(sys-0.4thy)(+0.6))x10(-3).