Transverse-Spin and Transverse-Momentum Effects in High-Energy Processes

Understand

The state of the art concerning transverse-spin and transverse-momentum phenomena in hard hadronic reactions is reviewed.

• An account is given of single-spin and azimuthal asymmetries in semiinclusive deep inelastic scattering, e^+ e^- annihilation, Drell-Yan production, and hadroproduction.
• The ongoing experiments and the main theoretical frameworks are described in the first part of the paper.
• The second part is devoted to the experimental findings and their phenomenological interpretations.