Measurement of the $\bar{B}\to D\ell\barν$ Partila Width and Form Factor Parameters

We have studied the decay $\bar{B} \to D\ell\barν$, where $\ell=e or μ$. From a fit to the differential decay rate $dΓ/dw$ we measure the rate normalization ${\cal F}_D(1)|V_{cb}|$ and form factor slope $\hatρ^2_D$, and, using measured values of $τ_B$, find $Γ(\bar{B} \to D\ell\barν) = (12.0 \pm 0.9 \pm 2.1) ns^{-1}$. The resulting branching fractions are ${\cal B}(\bar{B}^0 \to D^+\ell^-\barν)=(1.87 \pm 0.15 \pm 0.32)$ and ${\cal B}(B^- \to D^0\ell^-\barν)=(1.94 \pm 0.15 \pm 0.34)$. The form factor parameters are in agreement with those measured in $\bar{B} \to D^*\ell\barν$ decays, as predicted by heavy quark effective theory.

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