On the treatment of the $\Delta$-contribution in electromagnetic $pp$-knockout reactions

The treatment of the $\Delta$-current and its contribution in the exclusive $^{16}$O$(e,e'pp)^{14}$C and $^{16}$O$(\gamma,pp)^{14}$C knockout reactions are investigated in combination with the effects of correlations. Different parametrizations of the effective $\Delta$-current and different treatments of correlations in the two-nucleon overlap function are considered. The results are presented and discussed for a suitable choice of kinematics. It is found that the investigation of different mutually supplementing kinematics is necessary to resolve the uncertainties in the theoretical ingredients and extract clear and unambiguous information on correlations.