Orthogonality, antisymmetry and c.m. effects in direct photoreactions

The relevance of different approximations usually adopted in the description of direct knockout of nucleons in photoreactions at medium energies is investigated. Orthogonality between initial and final states in DWIA and antisymmetrization of the outgoing particle are studied in the presence of recoil terms arising from a correct treatment of the c.m. motion. The different effects are discussed in the specific example of the 12C target nucleus for different combinations of bound and scattering states. Whereas orthogonality and antisymmetrization appear to play a rather relevant role only at backward angles, the recoil term is particularly important for the (γ, n) reaction and cannot be simulated by the use of multipole energy-independent effective charges.