Azimuthal and single spin asymmetry in deep-inelastic lepton-nucleon scattering
The collinear expansion technique is generalized to the factorization of unintegrated parton distributions and other higher twist parton correlations from the corresponding collinear hard parts that involve multiple parton final state interaction. Such a generalized factorization provides a consistent approach to the calculation of inclusive and semi-inclusive cross sections of deep-inelastic lepton-nucleon scattering. As an example, the azimuthal asymmetry is calculated to the order of 1/Q in semi-inclusive deeply inelastic lepton-nucleon scattering with transversely polarized target. A non-vanishing single-spin asymmetry in the "triggered inclusive process" is predicted to be 1/Q suppressed with a part of the coefficient related to a moment of the Sivers function.