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

TL;DR

This paper measures the decay rate and form factor parameters of the semileptonic decay $ar{B} o D\, ext{l}ar{ u}$, providing experimental data consistent with heavy quark effective theory predictions.

Contribution

It presents the first detailed measurement of the differential decay rate and form factor parameters for $ar{B} o D\, ext{l}ar{ u}$ decays, including branching fractions and decay widths.

Findings

Measured decay width $ar{B} o D\, ext{l}ar{ u}$ as (12.0 ± 0.9 ± 2.1) ns$^{-1}$.

Determined branching fractions: (1.87 ± 0.15 ± 0.32)% for $ar{B}^0$ and (1.94 ± 0.15 ± 0.34)% for $B^-$.

Form factor parameters agree with those from $ar{B} o D^*\, ext{l}ar{ u}$ decays and heavy quark effective theory.

Abstract

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