Interpretation of the spin structure in nucleon-nucleon scattering

It is shown that the phase of the dominant non-flip amplitude is the key to an understanding of the rapid change of shape with energy of the polarising power P and the spin correlation parameter Asub(NN), as discovered in elastic pp and pn scattering recently. It then turns out that at FNAL-SPS energies generally all spin effects become small. Only in the dip region of the differential cross section, in particular when the dip is very deep, may one expect sizable values of P and Asub(NN). Large spin effects at high energies would demand a flip coupling of the pomeron. (author)