Disintegration of Nuclei byπ−-Mesons

Investigations of nuclear disintegrations induced by ${\pi }^{-}$-meson absorption in nuclear emulsions, exposed to the ${\pi }^{-}$-meson beam of the 130-in. Rochester cyclotron, have been carried out. The energy spectrum of the protons emitted from the absorptions shows two distinct processes occurring: (a) evaporation of nucleons from an excited nucleus and (b) emission of knock-on protons, brought about by the interaction of a ${\pi }^{-}$-meson with a multi-particle structure in the nucleus. Of the mesons ending in the emulsion, 10±2 percent give rise to protons with energies ≥30 Mev. Strong evidence is presented for the boson character of the ${\pi }^{-}$-meson.