Twist-4 contributions to the azimuthal asymmetry in SIDIS

TL;DR

This paper calculates the differential cross section for unpolarized SIDIS up to twist-4, analyzing the azimuthal asymmetry <cos2φ> and its nuclear dependence using TMD parton matrix elements.

Contribution

It provides the first leading-order calculation of SIDIS cross section including twist-4 effects and explores nuclear dependence of azimuthal asymmetry using a Gaussian model.

Findings

Twist-4 contributions significantly affect azimuthal asymmetry <cos2φ>.

Nuclear dependence of asymmetry is characterized by a Gaussian convolution model.

Results suggest measurable nuclear effects in SIDIS azimuthal asymmetries.

Abstract

We calculate the differential cross section for the unpolarized semi-inclusive deeply inelastic scattering (SIDIS) process $e^-+N \to e^-+q+X$ in leading order (LO) of perturbative QCD and up to twist-4 in power corrections and study in particular the azimuthal asymmetry $<cos2\phi>$. The final results are expressed in terms of transverse momentum dependent (TMD) parton matrix elements of the target nucleon up to twist-4. %Under the maximal two-gluon correlation approximation, these TMD parton matrix elements in a nucleus %can be expressed terms of a Gaussian convolution of that in a nucleon with the width given by the jet transport %parameter inside cold nuclei. We also apply it to $e^-+A \to e^-+q+X$ and illustrate numerically the nuclear dependence of the azimuthal asymmetry $<cos2\phi>$ by using a Gaussian ansatz for the TMD parton matrix elements.