  Neutrino oscillations are clear evidence for physics beyond the standard
model. The goal of next-generation neutrino oscillation experiments is to find
a non-zero $\theta_{13}$, the last mixing matrix element for which we only know
an upper limit. For this, next-generation long-baseline neutrino oscillation
experiments require an order of magnitude better sensitivities. In particular,
accelerator-based experiments such as T2K and NOvA experiments need (1) good
neutrino energy reconstruction for the precise measurement of $\Delta m^2_{32}$
and $sin^22\theta_{23}$, and (2) good background prediction to measure $\nu_e$
appearance signals. Current and near future high statistics neutrino
experiments, such as K2K, MiniBooNE, SciBooNE, MINOS, and MINERvA help both (1)
and (2) by precise signal and background channel measurements.
