  We study the feasibility of using neutrino-electron elastic scattering to
measure the neutrino flux in the DUNE neutrino oscillation experiment. The
neutrino-electron scattering cross section is precisely known, and the
kinematics of the reaction allow determination of the incoming neutrino energy
by precise measurement of the energy and angle of the recoiling electron. For
several possible near detectors, we perform an analysis of their ability to
measure neutrino flux in the presence of backgrounds and uncertainties. With
realistic assumptions about detector masses, we find that a liquid argon
detector, even with limitations due to angular resolution, is able to perform
better than less dense detectors with more precise event-by-event neutrino
energy measurements. We find that the absolute flux normalization uncertainty
can be reduced from ~8% to ~2%, and the uncertainty on the flux shape can be
reduced by ~20-30%.
