Longitudinally Polarized Photoproduction of Inclusive Hadrons at   Fixed-Target Experiments
  We present a detailed phenomenological study of spin-dependent single-inclusive high-p_T hadron photoproduction with particular emphasis on the kinematics relevant for the Compass and Hermes fixed-target experiments. We carefully examine the theoretical uncertainties associated with the only moderate transverse momenta accessible in such measurements and analyze the sensitivity of the relevant spin asymmetries to the gluon polarization in the nucleon as well as to the completely unknown parton content of circularly polarized photons. 
B. Jager, M. Stratmann, and W. Vogelsang