Simple classification of final state interaction effects in 4 He ( e , e ′ p ) scattering

A b s t r a c t The radius of interaction between the struck proton and spectator nucleons is close to the radius of short-distance two-nucleon correlations in nuclear matter, which makes final state interaction (FSI) an important background to production of protons with large missing momentum. We present a simple classification of the dominant FSI effects in 4 He(e, e ′ p) scattering and identify parts of the phase space dominated by FSI. At large missing momentum, final state interaction leads to a striking angular anisotropy of the missing momentum distribution, which has a prominent peak in transverse kinematics and smaller, forward-backward asymmetric, peaks in parallel kinematics. 1 Quasielastic (e, e ′ p) scattering on nuclei at large missing momentum p m is a relevant tool for investigation of short-distance nucleon-nucleon interaction (initial state two-nucleon correlations (ISC)) in the nuclear medium [1] and constitutes an important part of the CEBAF experimental program [2]. The measured p m distribution is distorted by final state interaction (FSI) of the struck proton in the target nucleus debris. The point we wish to make in this paper is that, in the CEBAF range of energies, the radius b o of the FSI is very close to the radius r c of ISC (see below). This makes FSI an important background in the production of protons with large p m , which may obscure the relation