Nuclear Internal Momentum Distributions

The nuclear internal momentum distributions of protons in light nuclei have been studied with the 340-Mev scattered proton beam from the synchrocyclotron. The two protons from a quasi-elastic scattering event are detected in coincidence, and the energy of one of them is magnetically analyzed. In the limit of the impulse approximation, conservation of energy and momentum can be employed to solve for the momentum of the struck proton. The best fit to the experimental data for beryllium was obtained with a Gaussian momentum density distribution with a $\frac{1}{e}$ value of about 20 Mev. Fermi (rectangular) and Chew-Goldberger distributions did not fit so well. Qualitative differences were observed between lithium, beryllium, and boron. The observed lithium spectrum was interpreted as being caused by two types of protons in lithium; two core protons that have a large momentum distribution and a third proton that has a rather low kinetic energy. This speculation was supported by the shape of the observed lithium spectrum, and by the relative yields from lithium, beryllium, and deuterium. The spectrum observed from beryllium indicated that the protons in beryllium have a larger momentum than the protons in the lighter elements studied. There were some indications that the fifth proton in boron may behave similarly to the third proton in lithium.