  It is shown that in the experiments dedicated for producing of polarized
beams of antiprotons during their passage through a polarized gas target placed
in a storage ring it is possible to measure not only spin-dependent total
cross-sections of antiproton scattering by the proton (deuteron), but also the
spin-dependent real part of the coherent zero-angle scattering amplitude in the
process of production of a polarized beam of antiprotons.
