Study of exclusive charmless semileptonic B decays and |Vub|.

We study semileptonic B decay to the exclusive charmless states π-, p/w, η, and η' using the 16 fb -1 CLEO Y(4S) data sample. We find B(B 0 → π - l + v) = (1.37 ± 0.15 stat ± 0. 11 sys ) × 10 -4 and B(B 0 → ρ - l + v) = (2.93 ± 0.37 stat ± 0.37 sys ) X 10 -4 and find evidence for B + → η'l + v, with B(B+ → η'l + v) = (2.66 ± 0.80 stat ± 0.56 sys ) × 10 -4 . From our B → πlv rate for q 2 > 16 GeV 2 and lattice QCD, we find |V ub | = (3.6 ± 0.4 stat ± 0.2 sys +0.6 -0.4thy ) × 10 -3 .