Measurements of Cross Sections for Pion Absorption by Nuclei

Cross sections for true absorption by nuclei (Al, Ti, Cu, Sn, Au) of pions (${\pi }^{\pm }$) in the energy range from 20 to 280 MeV were measured by a new method of detecting nuclear $\gamma$ rays following the reaction. The incident-energy dependence of the cross sections in the low-energy region ($T_{\pi }<50\mathrm{}$ MeV) was well reproduced by an optical-model calculation, while the higher-energy part seems to indicate complex mechanisms of pion absorption.