Measurements of Cross Sections for Pion Absorption by Nuclei

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