Negative Pion Capture From Rest on Complex Nuclei

The capture of negative pions from rest by light nuclei, primarily ${\mathrm{O}}^{16}$, is investigated by means of a shell-model calculation. The conventional pion-nucleon $ps-\left(\mathrm{ps}\right)\mathrm{}$ interaction is used to calculate the probability of one-nucleon and two-nucleon ejection from the nucleus. Due to the effects of distorted waves, one-nucleon ejection is not found to be suppressed as has been previously supposed but is comparable to the two-nucleon mode. It is also found that back-to-back ejection of a nucleon pair is dominant over parallel ejection, and that the capture probability as a function of the angle between an ejected pair will show structure.