Azimuthal and single-spin asymmetry in deep-inelastic lepton-nucleon scattering

We derive a general framework for describing semi-inclusive deep-inelastic lepton-nucleon scattering in terms of the unintegrated parton distributions and other higher-twist parton correlations. Such a framework provides a consistent approach to the calculation of inclusive and semi-inclusive cross sections including higher-twist effects. As an example, we calculate the azimuthal asymmetries to the order of $1/Q$ in semi-inclusive process with transversely polarized target. A nonvanishing 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.