Measurement of Branching Fractions and Form Factor Parameters of B → Dν and B → D∗ν Decays at BaBar

We use a global fit to determine the form factor slopes and branching fractions of the decays B → Dν and B → D∗ν. We reconstruct D pairs and con-struct a 3-dimensional distribution binned in lepton momentum, D momentum and cosΘB−D. These kinematic variables provide good separation between the signal and background. We fit electron and muon samples separately and combine them after calculating systematic uncertainties. The form factor slopes, ρ2D for B → Dν and ρ2 for B → D∗ν decays, are measured to be ρ2D = 1.22 ± 0.04 ± 0.07 and ρ2 = 1.21 ± 0.02 ± 0.07, where the errors are statistical and systematic, respectively. Branching fractions are fitted to be B(B+ → D̄0+ν) = (2.36 ± 0.03 ± 0.12) % and B(B+ → D̄∗0+ν) = (5.37 ± 0.02 ± 0.21) %. We use these results to determine the products, G(1)|Vcb | = (43.8±0.8±2.3)×10−3 and F(1)|Vcb | = (35.7±0.2±1.2)×10−3 iv of the form factors at zero recoil and the CKM matrix element |Vcb|, from which |Vcb| can be extracted using theoretical input