Multinucleon knockout in electron scattering

The exclusive (e,e’p) reaction and the inclusive (p,p’) reaction for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at intermediate energy are studied in order to understand the reaction mechanism leading to multinucleon knockout in electron scattering. We focus on the effect of the final-state interaction in the missing-energy spectrum measured (under parallel kinematics) in a coincidence (e,e’p) experiment in the dip region, where the many-body process is the dominant channel. To disentangle complex many-body processes and understand the final-state interaction quantitatively, we first study the inclusive (p,p’) reaction at the corresponding proton energy, which represents the final-state interaction in the on-shell limit. We show that the single scattering process, which means that the incident proton interacts inelastically with the target nucleon only once before coming out, is dominant at small proton scattering angles and can be treated within the framework of distorted-wave impulse approximation by using the effective nucleon-nucleon (NN) interaction. This prescription is able to be applied to the (e,e’p) reaction, since the forward proton scattering in the final state is important under parallel kinematics. Based on the knowledge obtained from the study of the (p,p’) reaction, we examine the two-body type of final-state interaction in electron scattering within the above approach. We indicate limitations of the two-body process as a mechanism for understanding the (e,e’p) reaction. Furthermore, the presence of the many-body mechanism involving more than two nucleons is speculated from qualitative investigations, and some possible experiments which could provide important information on the many-body mechanism are suggested.