A Study Of Exclusive Charmless Semileptonic B Decays With The Cleo Detector

We report on a study of exclusive semileptonic b → u decays in 9.7 million BB¯ events accumulated with the CLEO detector produced in the Cornell Electron Storage Ring (CESR). We reconstruct candidates in the exclusive decay modes B → [π±, π0, ρ ±, ρ0, ω, η]ℓν, where the charged lepton is an electron or a muon. We use the hermeticity of the CLEO detector to infer the neutrino four momentum. The ISGW2 theoretical calculation of the B → Xu form factors is used to determine total branching fractions, the partial widths as a function of the momentum transfer q2, and an estimate of the CKM matrix element |Vub|. We find a value for the B → π±ℓν branching fraction of ( 1.470±0.179+0.129- 0.150 ) × 10−4 and a value of ( 1.657±0.228+0.421-0.481 ) × 10−4 for the B → ρ ±ℓν branching fraction. We also report a value of ( 0.837±0.306+0.082-0.092 ) × 10−4 for the B → ηℓν branching fraction. Finally, we find a value of |Vub| of ( 2.913±0.128+0.165-0.220 ) × 10−3