Meson exchange currents in a relativistic model for electromagnetic one   nucleon emission
  We analyze the role of meson exchange currents (MEC) in photon- and electron-induced one nucleon emission reactions in a fully relativistic model. The relativistic mean field theory is used for the bound state and the Pauli reduction for the scattering state. Direct 1-body and exchange 2-body terms in the nuclear current are considered. Results for the 12C(gamma,p) and 16O(gamma,p) differential cross sections and photon asymmetries are displayed in an energy range between 60 and 196 MeV. The 2-body seagull current affects the cross section less than in nonrelativistic analyses. In the case of the 16O(gamma,n) differential cross section MEC effects are large but not sufficient to reproduce the data. MEC have a small effect on (e,e'p) calculations. 
Andrea Meucci, Carlotta Giusti, and Franco Davide Pacati