Investigations of azimuthal asymmetry in semi-inclusive leptoproduction

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 \(\langle \cos\phi \rangle\) and \(\langle \cos2\phi \rangle\) are significant. We also reconsider the results of perturbative effects for \(\langle \cos\phi \rangle\) at large momentum transfers [1] using the more recent sets of scale-dependent distribution and fragmentation functions, which bring up to 18% difference in \(\langle \cos\phi \rangle\). In the same approach we calculate the \(\langle \cos2\phi \rangle\) as well.