Measurements of the semileptonic decays B̄→Dν̄ and B̄→D*ν̄ using a global fit to DXν̄ final states

Semileptonic B̄ decays to DXν̄ (=e or μ) are selected by reconstructing D0 and D+ combinations from a sample of 230×106 Υ(4S)→BB̄ decays recorded with the BABAR detector at the PEP-II e+e- collider at SLAC. A global fit to these samples in a three-dimensional space of kinematic variables is used to determine the branching fractions B(B-→D0ν̄)=(2.34±0.03±0.13)% and B(B-→D *0ν̄)=(5.40±0.02±0.21)% where the errors are statistical and systematic, respectively. The fit also determines form-factor parameters in a parametrization based on heavy quark effective theory, resulting in ρD2=1.20±0.04±0.07 for B̄→Dν̄ and ρD*2=1.22±0.02±0.07 for B̄→D*ν̄. These values are used to obtain the product of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| times the form factor at the zero recoil point for both B̄→Dν̄ decays, G(1)|Vcb|=(43.1±0.8±2.3) ×10-3, and for B̄→D*ν̄ decays, F(1)|Vcb|=(35.9±0.2±1.2)×10-3.