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 pT inclusive hadron production processes, AB → C X, by incorporating quark intrinsic motion in the spin dependent quark distribution and fragmentation functions. We concentrate here on spin and k⊥ effects in the fragmentation process of a polarized quark into the observed hadron, and give predictions for STSA in semi-inclusive deep inelastic scattering, lp → πX and γp → πX. Polarized inclusive hadron production processes at high energies and pT , A, SA +B, SB → C X, can be described in the formalism of perturbative QCD (pQCD), by using the factorization theorem at leading twist; the corresponding cross section reads