Azimuthal and Single Spin Asymmetries in Hard Scattering Processes

Understand

In this article we review the present understanding of azimuthal and single spin asymmetries for inclusive and semi-inclusive particle production in unpolarized and polarized hadronic collisions at high energy and moderately large transverse momentum.

• After summarizing the experimental information available, we discuss and compare the main theoretical approaches formulated in the framework of perturbative QCD.
• We then present in some detail a generalization of the parton model with inclusion of spin and intrinsic transverse momentum effects.
• In this context, we extensively discuss the phenomenology of azimuthal and single spin asymmetries for several processes in different kinematical configurations.