Nuclear dependence of azimuthal asymmetry in semi-inclusive deep inelastic scattering

Within the framework of a generalized factorization, semi-inclusive deeply inelastic scattering (SIDIS) cross sections can be expressed as a series of products of collinear hard parts and transverse-momentum-dependent (TMD) parton distributions and correlations. The azimuthal asymmetry of unpolarized SIDIS in the small transverse-momentum region will depend on both twist-2 and -3 TMD quark distributions in target nucleons or nuclei. Nuclear broadening of these twist-2 and -3 quark distributions due to final-state multiple scattering in nuclei is investigated and the nuclear dependence of the azimuthal asymmetry is studied. It is shown that the azimuthal asymmetry is suppressed by multiple parton scattering and the transverse-momentum dependence of the suppression depends on the relative shape of the twist-2 and -3 quark distributions in the nucleon. A Gaussian ansatz for TMD twist-2 and -3 quark distributions in nucleon is used to demonstrate the nuclear dependence of the azimuthal asymmetry and to estimate the smearing effect due to fragmentation.