On the Interaction of Low Energy Pions with Nuclei

Abstract

It is shown that the low energy [Formula: see text] pion–nucleus optical potential, which has previously been derived by other authors from a microscopic point of view, has a simple geometric structure which can be understood from the analogous problem of adding electric potentials in a dielectric medium. The optical properties of this potential are dominated by the presence of a short-range local repulsion, which is comparable to the energies of interest, and by a strong momentum dependence in the optical interaction. It is shown that, because momentum-dependent processes are strongly suppressed near the top of the resulting potential barrier and because the nuclear density enters the optical interaction in a transparent manner, such momentum-dependent processes as pion absorption provide an excellent tool for investigating the structure of the nuclear surface. Such processes should finally resolve current inconsistencies in the knowledge of the neutron distribution in the nuclear surface.