Angular distributions of Sc fragments from the interaction ofU238with 0.8-400 GeV protons

Angular distributions of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Sc}_{}^m{}_{}{}^{}$, ${}_{}{}^{46}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{47}{}_{}{}^{}\mathrm{Sc}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ emitted in the interaction of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ with 0.8, 3.0, 11.5, and 400 GeV protons have been measured. The angular distributions peak at forward angles at 0.8 and 3 GeV but are sideward-peaked at 11.5 and 400 GeV. At 400 GeV, fewer fragments are emitted at forward than at backward angles. Isotopic differences were found to be small. The data were fitted with the function $F_L\left({\theta }_L\right)=1+A_1{cos\theta }_L+A_2{{cos}^2\theta }_L$ and were also analyzed in terms of the two-step model. The values of $A_1$ peak at 3 GeV, go through zero at 11.5 GeV, and become negative at 400 GeV. The values of $A_2$ are zero at 0.8 GeV and become increasingly negative with increasing proton energy. A qualitative explanation in terms of a possible change in the nature of proton-nucleus interactions at high energies is presented.