Virtual pion scattering

Abstract We explore coherent pion production in ( 3 He, 3 H π + ) and (p,n π + ) reactions as effective virtual pion scattering, in calculations of cross sections to the ground state and low-lying excitations of the target nucleus. Our coupled-channel model includes a source term emulating a virtual-pion beam and an optical potential for the interaction of the pion in the medium. We demonstrate that the landmark lowering of the peak in the energy-transfer spectra is entirely determined by the rescattering of the pion, and that its low-energy wing is sensitive to the pion-nucleon s -wave amplitude including its off-shell behavior.