  We calculate the cross sections for elastic nu_l + e -> nu_l + e and antinu_l
+ e -> antinu_l + e scattering (l=e, mu or tau) in the Born approximation and
with exactly fixed polarization states of target and final-state electrons,
discussing their sensitivity to the incident (anti)neutrino flavor. We suggest
investigation of the flavor composition of a (anti)neutrino beam by a
flux-independent analysis of the scattering of its constituents off polarized
electrons.
