Spin Dependence in Inclusive Reactions

We treat the spin dependences of high-energy inclusive reactions from the viewpoint of a $J$-plane analysis. Measurements of various spin correlations are shown to bear directly on questions such as factorization of residues at Regge poles and the strengths of $J$-plane cuts. We provide examples of experiments which test these ideas using polarized beams, polarized targets, or polarized products. Electroproduction and high-energy neutrino reactions are viewed as sources for polarized spin-one "beams," and the implications for the processes are drawn in detail. Finally, we consider scaling properties of these latter reactions and discuss produced-particle multiplicity in the scaling region.