Mechanisms in the C-12(gamma,pn) and (gamma,pp) reactions.

12 C(gamma,pn) and (gamma,pp) cross sections have been measured in kinematics which emphasize direct 2N knockout for E(gamma) =­ 120 - 400 MeV and theta(p) = ­23 - 152 deg. The cross sections for both reactions peak strongly in the Delta-resonance region. Theoretical calculations that account for the medium dependence of the Delta propagator predict a similar photon energy dependence to the data and describe the general trends of the measured (gamma,pp)/(gamma,pn) ratio. Both cross sections show strong angular dependence, and the large differences between the two channels indicate different microscopic reaction mechanisms.