Collective Resonances in Pion-Nucleus Scattering

Abstract

Pion-nucleus scattering is described by the excitation of bound nucleons into the $\Delta$ resonance leading to isobaric resonances of the whole nucleus. A few broad collective resonances of different multipolarity are shown to dominate elastic and inelastic $\pi$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ scattering. From the qualitatively good agreement with the data, we conclude that those giant isobaric resonances are a general feature of the nuclear excitation spectrum in the $\Delta (3, 3)$ energy range.