Investigations of Azimuthal Asymmetry in Semi-Inclusive Leptoproduction

Abstract

We consider the azimuthal asymmetries in semi-inclusive deep inelastic leptoproduction arising due to both perturbative and nonperturbative effects at HERMES energies and show that the $k_T^2/Q^2$ order corrections to $<\cos \varphi >$ and $<\cos 2\varphi >$ are significant. We also reconsider the results of perturbative effects for $<\cos \varphi >$ at large momentum transfers \cite{A1} using the more recent sets of scale-dependent distribution and fragmentation functions, which bring up to 18{%} difference in $<\cos \varphi >$. In the same approach we calculate the $<\cos 2\varphi >$ as well.

Comments: 8 pages, LaTeX, 6 PS figures, final version, to appear in EPJC