New Interpretation of the Pion-Nucleus Optical Potential for Pionic Atoms

Abstract

We show that if the $P$-wave interaction volumes relevant for construction of the pionnucleus optical potential used in pionic-atom studies turn out to be simply related empirically to the free-space pion-nucleon scattering volumes, then this would be indicative of both sets of quantities being dominated by the $\ensuremath{\Delta}(1236 \mathrm{MeV})$, which can be treated as an independent baryonic excitation in nuclei. Within this framework, we give a simple derivation of modifications to the optical potential coming from baryon-baryon short-range correlations.