Spin effects in large-transverse-momentum exclusive scattering processes

Nucleon-nucleon scattering at large momentum transfer is analyzed within the framework of quantum-chromodynamic quark and gluon interactions. The spin dependence of the hadronic amplitude is found to be particularly sensitive to the underlying dynamical mechanisms. Detailed discussions of the quark-intercharge and Landshoff pinch-singularity contributions are given for large-angle $\mathrm{pp}$, $\mathrm{np}$, and $p\overline{p}$ elastic scattering. A possible explanation is given for the large spin-spin correlations measured by Crabb et al. We also define a new SU(2) symmetry group, $H$ spin, which generalizes conventional helicity, and is an exact symmetry of the quark-intercharge process.