Angular Distributions and Mechanisms of Fragmentation by Relativistic Heavy Ions

Angular distributions of massive fragments from relativistic heavy-ion interactions are reported. Sideward peaking is observed for the light fragment ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$, from 25-GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + Au, while the distribution for ${}_{}{}^{127}{}_{}{}^{}\mathrm{Xe}$ is strongly forward peaked. Conflicts of these observations and other existing data with predictions of models for the fragmentation process are discussed.