The (π⁺, 2p) Reactions on Nuclei

Abstract

When a slow pion is absorbed in a nucleus by a single nucleon which takes all the available energy, the conservation of energy and momentum requires the nucleon to have a large momentum inside the nucleus before the absorption process. For a pion at rest this momentum would be 500 MeV/c, and it is known that not many nucleons have such high momenta. In the case of an absorption by a pair of nucleons, on the other hand, energy and momenta are easily balanced, the two nucleons going in opposite directions with a high relative momentum and a small momentum of their center of mass. The fact that the absorption by a pair of nucleons is favored makes pion absorption an ideal tool for the study of residual states with two holes in the internal shells.

U.S. National Science Foundation Senior Postdoctoral Fellow, on leave from Stanford University, California, USA, 1966–7.