Probing the lifetime of excited composite nuclei with particle-particle correlations

Particle-particle correlation techniques can be applied to small angle coincidence measurements where the primary source of the detected particles is thought to be a statistically equilibrated composite nucleus. Such application allows one to investigate the lifetimes in such systems and probe the limits of the statistical model for high excitations. In this paper data are shown for the small angle particle-particle correlations from the reactions 80, 140, 215, and 250 MeV 16O + 27Al giving p-p, p-d, p-α, d-α, and α-α pairs. In addition the results from n-p, n-d, and n-α measurements at 215 MeV will be presented. Finally, the results from 32S + 27Al at 105 and 215 MeV will be shown. The correlations are seen to be weak at the lowest energies and become progressively stronger with increasing excitation energy. Simulations of the correlation functions which include: lifetimes and decay probabilities based on the statistical model, particle trajectories, and cooling of the source, will be compared to the measured results. The general trends of the p-p, p-d and n-d data are well reproduced by the simulations. However, the correlations of other particle pairs are complicated by the sequential breakup of particle unbound states such as 8Be or 6Li. Some preliminary results where this process is included will be shown