Measurements of the semileptonic decays ¯¯¯B→Dℓ¯ν and¯¯¯B→D∗ℓ¯ν using a global fit to DXℓ¯ν final states

Abstract

Semileptonic ¯¯¯ B decays to D X ℓ ¯ ν ( ℓ = e or μ ) are selected by reconstructing D 0 ℓ and D + ℓ combinations from a sample of 230 × 10 6 Υ ( 4 S ) → B ¯¯¯ B 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 − → D 0 ℓ ¯ ν ) = ( 2.34 ± 0.03 ± 0.13 ) % and B ( B − → D * 0 ℓ ¯ ν ) = ( 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 ρ 2 D = 1.20 ± 0.04 ± 0.07 for ¯¯¯ B → D ℓ ¯ ν and ρ 2 D ∗ = 1.22 ± 0.02 ± 0.07 for ¯¯¯ B → D ∗ ℓ ¯ ν . These values are used to obtain the product of the Cabibbo-Kobayashi-Maskawa matrix element | V c b | times the form factor at the zero recoil point for both ¯¯¯ B → D ℓ ¯ ν decays, G ( 1 ) | V c b | = ( 43.1 ± 0.8 ± 2.3 ) × 10 − 3 , and for ¯¯¯ B → D ∗ ℓ ¯ ν decays, F ( 1 ) | V c b | = ( 35.9 ± 0.2 ± 1.2 ) × 10 − 3 .