  Recent measurements of the cosmic-ray electron (e-) and positron (e+) fluxes
show apparent excesses compared to the spectra expected by standard cosmic-ray
(CR) propagation models in our galaxy. These excesses may be related to
particle acceleration in local astrophysical objects, or to dark matter
annihilation/decay. The e+/e- ratio (measured up to ~100 GeV) increases
unexpectedly above 10 GeV and this may be connected to the excess measured in
all-electron flux at 300-800 GeV. Measurement of this ratio at higher energies
is a key parameter to understand the origin of these spectral anomalies.
Imaging Atmospheric Cherenkov Telescopes (IACT) detect electromagnetic air
showers above 100 GeV, but, with this technique, the discrimination between
primary e-, e+ and diffuse gamma-rays is almost impossible. However, the Moon
and the geomagnetic field provide an incredible opportunity to separate these 3
components. Indeed, the Moon produces a 0.5deg-diameter hole in the isotropic
CR flux, which is shifted by the Earth magnetosphere depending on the momentum
and charge of the particles. Below few TeV, the e+ and e- shadows are shifted
at >0.5deg each side of the Moon and the e+, e- and gamma-ray shadows are
spatially separated. IACT can observe the e+ and e- shadows without direct
moonlight in the field of view, but the scattered moonlight induces a very high
background level. Operating at the highest altitude (2200m), with the largest
telescopes (17m) of the current IACT, MAGIC is the best candidate to reach a
low energy threshold in these peculiar conditions. Here we discuss the
feasibility of such observations.
