Unusual Backward Enhancement in the Angular Distribution of Products from the Interaction ofU238with 400-GeV Protons

Angular distributions of various Mg, Sc, Cu, Ag, and Ba nuclides produced in the interaction of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ with 400-GeV protons have been measured. While all the angular distributions peak at ∼ 90°, those obtained for certain products are characterized by greater backward than forward emission in the laboratory system. This category includes both neutron-deficient and neutron-excess Sc fragments as well as neutron-deficient Cu and Ag nuclides.