Measurement of the B → Dℓν branching fractions and form factor

Using a sample of 3.3 × 10 B-meson decays collected with the CLEO detector at the Cornell Electron Storage Ring, we have studied B → D ℓ ν and B → D ℓ ν decays, where ℓ can be either e or μ . We distinguish B → Dℓν from other B semileptonic decays by examining the net momentum and energy of the particles recoiling against D - ℓ pairs. We find Γ(B → Dℓν) = (14.1±1.0±1.2)ns and derive branching fractions for B → D ℓ ν and B → D ℓ ν of (2.32±0.17±0.20)% and (2.20±0.16±0.19)%, respectively, where the uncertainties are statistical and systematic. We also investigate the B → Dℓν form factor and the implication of the result for |V |. © 1999 The American Physical Society. 6 - 0 - 0 + - - - - -1 - 0 - 0 + - c