Abstract
We applied collinear expansion to the semi-inclusive deeply inelastic lepton-nucleon (nucleus) scattering process [Formula: see text] with both polarized beam and polarized target up to twist-3, and unpolarized process up to twist-4. The differential cross section and azimuthal asymmetries are expressed in terms of gauge invariant twist-3 and twist-4 TMD parton distribution/correlation functions. Measurements of such azimuthal asymmetries provide methods to study different spin and transverse momentum aspects of the partonic structure of nucleon. We further study the nuclear dependence of azimuthal asymmetries and adopt Gaussian ansatz for TMD distribution/correlation functions to estimat the semi-quantitive behaviour of the nuclear dependence. We predict the A-dependence of azimuthal asymmetries which can be tested in the planned EIC’s.
Highlights
Semi-inclusive deeply inelastic lepton-nucleon scattering (SIDIS) provides a nice place to study the spin- and transverse-momentum-dependent(TMD) parton distribution functions
Measurements of azimuthal asymmetries of final state hadron(jet) of SIDIS has been done in Hermes, COMPASS and JLab, and they are proposed to be important observables for the planned electron-ion colliders (EIC’s)
Various azimuthal asymmetries can be obtained from above cross sections, and they are proportional to the ratios of different TMD parton distribtuion/correlation functions
Summary
Semi-inclusive deeply inelastic lepton-nucleon scattering (SIDIS) provides a nice place to study the spin- and transverse-momentum-dependent(TMD) parton distribution functions. The fundamental QCD TMD factorization at twist-3 or higher twist level is not proved yet, and very little quantitative informaiton of higher twist parton correlation functions is extracted from experimental data This is an Open Access article published by World Scientific Publishing Company. We adopt collinear expansion in inclusive DIS1–3 and applied this technique to SIDIS.[4,5,6,7,8] We obatin gauge invariant hadronic tensors and differential cross sections. One just need to expand the gauge invariant correlation matrices with γ-matrices to obtain the TMD parton distribution/correlation functions, and employ QCD equation of motion to simplify the final results for the hadronic tensor, which will be electromagnetic and color gauge invariant.
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