Nuclear-structure studies with pions and heavy ions. Progress report, June 1, 1980-May 31, 1981

Experiments performed at the Los Alamos Meson Physics Facility yielded very striking results. In inelastic pion scattering from 14C near the [3,3] resonance cross sections ratios R = sigma(π+)/sigma(π-) and R-1 = sigma(π-)/sigma(π+) were observed that are significantly larger than the free pion-nucleon values. These results were interpreted as due to strong cancellations of the neutron and proton components in the transition amplitude. Measurements of 13C(π,π') excitation functions between 100 and 300 MeV at two momentum transfers showed dramatically different energy dependencies for ΔS =0 and ΔS = 1 transitions. They were used to derive nuclear structure information on several highly excited states. Pion data for other nuclei (12C, 16O, 40Ca, etc.) were analyzed and information on isospin mixing, the double-charge-exchange reaction mechanism, and the excitation of collective states was extracted. Further data were taken with a 547 MeV proton beam on 13C. The data taking for the (t,t') and (3He,3He') reactions at the Los Alamos Van de Graaff has been completed. The continuing studies of the heavy-ion nucleus optical potential yielded information on very systematic dependencies of the potential depths on the incident energy