  We present a lattice QCD calculation of the $B \rightarrow D l \nu$
semileptonic decay form factors $f_+(q^2)$ and $f_0(q^2)$ for the entire
physical $q^2$ range. Non-relativistic QCD (NRQCD) bottom quarks and Highly
Improved Staggered Quark (HISQ) charm and light quarks are employed together
with $N_f = 2+1$ MILC gauge configurations. A joint fit to our lattice and
BaBar experimental data allows an extraction of the CKM matrix element
$|V_{cb}|$. We also determine the phenomenologically interesting ratio $R(D) =
{\cal B}(B \rightarrow D \tau \nu_\tau) / {\cal B}(B \rightarrow D l \nu_l)$
($l = e, \mu$). We find $|V_{cb}|_{excl.}^{B \rightarrow D} = 0.0402(17)(13)$,
where the first error consists of the lattice simulation errors and the
experimental statistical error and the second error is the experimental
systematic error. For the branching fraction ratio we find $R(D) = 0.300(8)$.

High Energy Physics - Lattice;High Energy Physics - Phenomenology