  The CKM matrix element $|V_{cb}|$ can be extracted by combining
experimentally determined branching fractions for $\bar{B}\to
D^{(*)}\ell\bar{\nu}$ decays with form factors from the lattice. While
successful, the precision of this approach has been limited by heavy-quark
discretization effects. An improved version of the Fermilab action, the
Oktay-Kronfeld action, can be used to reduce heavy-quark discretization effects
in calculations performed at the physical bottom and charm quark masses.
Treating charm and bottom quarks as massive, we are carrying out improvement of
the flavor-changing currents through third order in the momentum (HQET)
expansion.
