Azimuthal asymmetry in lepton-proton scattering at high energies

Abstract
We consider the azimuthal angular dependence of the distribution of final-state hadrons in high-energy lepton-proton scattering. The distribution displays an azimuthal asymmetry due to both perturbative and nonperturbative effects. At the large momentum transfers attainable, for example, at the DESY ep collider HERA we expect the perturbative effects to dominate and constitute a clear test of QCD.