Selectivity of the16O(e,e′pp)reaction to discrete final states

Resolution of discrete final states in the ${}^{16}\mathrm{O}{(e,e}^{\prime }{pp)}^{14}\mathrm{C}$ reaction may provide an interesting tool to discriminate between contributions from one- and two-body currents in this reaction. This is based on the observation that the $0^{+}$ ground state and first $2^{+}$ state of ${}^{14}\mathrm{C}$ are reached predominantly by the removal of a ${}^1{S}_0$ pair from ${}^{16}\mathrm{O}$ in this reaction, whereas other states mostly arise by the removal of a ${}^{3}P$ pair. This theoretical prediction has been supported recently by an analysis of the pair momentum distribution of the experimental data [1]. In this paper we present results of reaction calculations performed in a direct knockout framework where final-state interaction and one- and two-body currents are included. The two-nucleon overlap integrals are obtained from a calculation of the two-proton spectral function of ${}^{16}\mathrm{O}$ and include both long-range and short-range correlations. The kinematics chosen in the calculations is relevant for recent experiments at NIKHEF and Mainz. We find that the knockout of a ${}^{3}P$ proton pair is largely due to the (two-body) Δ current. The ${}^1{S}_0$ pair knockout, on the other hand, is dominated by contributions from the one-body current and therefore sensitive to two-body short-range correlations. This opens up good perspectives for the study of these correlations in the ${}^{16}\mathrm{O}{(e,e}^{\prime }pp)$ reaction involving the lowest few states in ${}^{14}\mathrm{C}.$ In particular the longitudinal structure function $f_{00},$ which might be separated with superparallel kinematics, turns out to be quite sensitive to the $\mathrm{NN}$ potential that is adopted in the calculations.