  The T2K experiment is a long-baseline neutrino oscillation experiment with
the ability to measure precisely $\nu_{\mu}\rightarrow\nu_e$ and
$\nu_{\mu}\rightarrow\nu_{\mu}$ oscillations. Control of systematic
uncertainties-dominated by flux and cross section uncertainties-is critical for
the precision of these measurements. An analysis of charged current $\nu_{\mu}$
interactions at the T2K near detector significantly reduces these
uncertainties, from 26.9% to 3.0% for the current $\nu_{\mu}\rightarrow\nu_e$
measurement at T2K.
