Pion-nucleus optical potential valid up to the Δ-resonance region

We present in this article an optical potential for the π-nucleus interaction that can be used in various studies involving π-nucleus channels. Based on earlier treatments of the low-energy π-nucleus optical potential, we have derived a potential expression applicable from threshold up to the Δ-resonance region. We extracted the impulse approximation form for this potential from the π-N scattering amplitude and then added to it kinematical and physical corrections. The kinematic corrections arise from transforming the impulse approximation expression from the π-N center of mass frame to the π-nucleus center of mass frame, while the physical corrections arise mostly from the many-body nature of the π-nucleus interaction. By taking advantage of the experimental progress in our knowledge of the π-N process, we have updated earlier treatments with parameters calculated from state-of-the-art experimental measurements.