  The light dark matter model can explain both the primordial abundance of dark
matter and the anomalous 511 keV gamma-ray signal from the galactic center.
This model posits a light neutral scalar, \chi, with a mass in the range 1 MeV
< Mchi < 10 MeV, as well as a light neutral spin-1 boson, U, which mediates the
annihilation channel \chi\chi -> e+e-. Since the dark matter particle is light,
its number density is relatively large if it accounts for a local dark matter
density of 0.3 GeV/cm^3. We consider an experiment in which a low-energy,
high-current electron beam is passed through a long evacuated tube, and elastic
scattering of electrons off dark matter particles is observed. The kinematics
of this process allow a clean separation of the signal process from scattering
off residual gas in the tube, and also a direct measurement of Mchi.
