  Using a generalized parton model approach including spin and intrinsic parton
motion effects, and assuming the validity of factorization for large p_T jet
production in hadronic collisions, we study the azimuthal distribution around
the jet axis of leading pions, produced in the jet fragmentation process. We
identify the observable leading-twist azimuthal asymmetries for the unpolarized
and single-polarized case related to both quark and gluon-originated jets. We
account for all physically allowed combinations of the transverse momentum
dependent (TMD) parton distribution and fragmentation functions, with special
attention to the Sivers, Boer-Mulders, and transversity quark distributions,
and to the Collins fragmentation function for quarks (and to the analogous
functions for gluon partons).
