Study of the mechanism of the reaction ^{4}He(e,e’p)^{3}H

A serious breakdown of the distorted-wave impulse approximation has recently been observed in the proton-knockout reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(e,e’p${)}^3$H. In the phenomenological description of the data, charge-excnange contributions were included through a coupled-channel calculation. New data obtained in a wide range of kinematical configurations are presented in order to study the anomaly in more detail. Its magnitude and dependence on momentum transfer are well accounted for by a newly presented microscopic description of various interaction effects, including meson-exchange currents and charge-exchange processes.