New Direct Reaction: Two-Proton Knockout from Neutron-Rich Nuclei

Abstract

The reaction $^{9}\mathrm{B}\mathrm{e}(^{28}\mathrm{M}\mathrm{g},^{26}\mathrm{N}\mathrm{e}+\ensuremath{\gamma})X$ has been studied at $82\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}$ together with two similar cases, $^{30}\mathrm{M}\mathrm{g}$ and $^{34}\mathrm{S}\mathrm{i}$. Strong evidence that the reactions are direct is offered by the parallel-momentum distributions of the reaction residues and by the inclusive cross sections. The pattern of the partial cross sections for $^{28}\mathrm{M}\mathrm{g}$ suggests the presence of correlations. A preliminary theoretical discussion based on eikonal reaction theory and the many-body shell model is presented. The reaction holds great promise for the study of neutron-rich nuclei.