We examine the essentials of the pion capture reaction (${\mathrm{\pi }}^{\mathrm{-}}$,p) with the pion captured directly into an atomic orbit. The reaction is a promising candidate for the population of the 1s or 2p atomic levels of medium to heavy nuclei. These levels have never been observed, but rather reliable theoretical calculations indicate that they have relatively small widths. One reason for interest in these levels is that they give a direct measurement of the threshold pion-nucleus amplitude, which has a bearing on questions such as chiral-symmetry breaking in the nuclear medium and the anomalously small level shifts and widths of some of the more deeply-bound pionic atoms. The differential cross section for the process is calculated using the distorted-wave impulse approximation. It is found that for medium-mass nuclei and incident pion beams of 20–50 MeV cross sections of the order of microbarns, well within the capability of present meson factories, can be expected. The related process (${\mathrm{\pi }}^{\mathrm{-}}$,n) is also studied.

• Received 6 March 1992

DOI:https://doi.org/10.1103/PhysRevC.46.1474