Single transverse spin asymmetries for semi-inclusive pion production in DIS

We present a phenomenological approach to the description of single transverse spin asymmetries (STSA) in inclusive hadron production. It generalizes the pQCD formalism for high energies and large p_T inclusive hadron production processes, A+B -> C+X, by incorporating quark intrinsic motion in the spin dependent quark distribution and fragmentation functions. We concentrate here on spin and k_T effects in the fragmentation process of a polarized quark into the observed hadron, and give predictions for STSA in semi-inclusive deep inelastic scattering, l + p -> pion + X and gamma^* + p -> pion + X.