True absorption and scattering of pions on nuclei

Abstract

The cross section for true absorption of pions in nuclei was obtained from experiments at 85, 125, 165, 205, 245, and 315 MeV for positive pions and at 125 and 165 MeV for negative pions. The results are compared with theoretical calculations. The inclusive pion scattering angular distribution was also measured, and the results indicate that quasifree scattering plays an important role for backward scattering. The total pion-nucleus cross section is decomposed into its major channels: elastic scattering, inclusive inelastic scattering, true absorption, and single charge exchange, as a function of pion energy and charge. For light nuclei, the true absorption cross section has a strong energy dependence, reflecting the shape of the (3,3) resonance. The $A$ dependence of the true absorption cross section is much stronger than that of the inclusive inelastic scattering.NUCLEAR REACTIONS Li, C, Al, Fe, Nb, Bi (${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}},{\ensuremath{\pi}}^{\ensuremath{'}}$); measured $\ensuremath{\sigma}({\ensuremath{\theta}}_{{\ensuremath{\pi}}^{\ensuremath{'}}})$, ${E}_{{\ensuremath{\pi}}^{+}}=85, 125, 165, 205, 245, \mathrm{and} 315$ MeV, ${E}_{{\ensuremath{\pi}}^{\ensuremath{-}}}=125, 165$ MeV; deduced ${\ensuremath{\sigma}}_{\mathrm{inelastic}}$, ${\ensuremath{\sigma}}_{\mathrm{absorption}}$; decomposition of ${\ensuremath{\sigma}}_{\mathrm{tot}}$.