Interactions of pions with nuclei

The role of pions as an important probe of nuclear structure has been discussed. The information one obtains from pion-nuclear interactions is complementary to and in some way more than what is obtained from the conventional nuclear probes. The recent wealth of experimental data obtained from the improved pion spectrometer facilities have led to intensive theoretical work. In particular the simultaneous study of π+ and π- experiments, once the Coulomb effects are properly accounted for should in principle yield valuable information on neutron densities. The present status of low and intermediate energy pion-nuclear interactions has been reviewed. The qualitative agreement between static first order calculations and the data at intermediate energies was clearly shown to break down at low energies. At low energies the scattering is relatively free of the effect of (3-3) resonance which dominates the interaction at 100-300 MeV. Hence the pion can penetrate into the nuclear interior and becomes a probe of properties of nuclear matter rather than simply of the nuclear surface. (author)