A phenomenological analysis of azimuthal asymmetries in unpolarized semi-inclusive deep inelastic scattering

TL;DR

This paper analyzes azimuthal asymmetries in unpolarized semi-inclusive deep inelastic scattering using recent experimental data, focusing on intrinsic transverse momentum effects and higher-twist contributions within the TMD framework.

Contribution

It provides a phenomenological analysis incorporating recent multidimensional data, emphasizing the role of Cahn, Boer-Mulders effects, and higher-twist contributions at low Q^2.

Findings

Cahn and Boer-Mulders effects significantly influence azimuthal asymmetries.

Higher-twist contributions are important at low Q^2.

Fits are affected by the dominance of low-Q^2 kinematics.

Abstract

We present a phenomenological analysis of the cos-phi and cos-2phi asymmetries in unpolarized semi-inclusive deep inelastic scattering, based on the recent multidimensional data released by the COMPASS and HERMES Collaborations. In the TMD framework, valid at relatively low transverse momenta, these asymmetries arise from intrinsic transverse momentum and transverse spin effects, and from their correlations. The role of the Cahn and Boer-Mulders effects in both azimuthal moments is explored up to order 1/Q. As the kinematics of the present experiments is dominated by the low-Q^2 region, higher-twist contributions turn out to be important, affecting the results of our fits.