Center-of-mass effects in electromagnetic two-proton knockout reactions

The role of center-of mass (CM) effects in the one-body nuclear current in the description of electromagnetically induced two-nucleon knockout reactions is discussed in connection with the problem of the lack of orthogonality between initial bound states and final scattering states obtained by the use of an energy-dependent optical model potential. Results for the cross-sections of the exclusive 16O(e, e'pp)14C and 16O(γ, pp)14C knockout reactions in different kinematics are presented and discussed. In super-parallel kinematics CM effects produce a strong enhancement of the 16O(e, e'pp)14Cg.s. cross-section which strongly reduces the destructive interference between the one-body and Δ-current and the sensitivity to the treatment of the Δ-current found in previous work.