Elastic scattering of pions from finite nuclei is investigated utilizing a contemporary, momentum-space first-order optical potential combined with microscopic estimates of second-order corrections. The calculation of the first-order potential includes: (1) full Fermi-averaging integration including both the delta propagation and the intrinsic nonlocalities in the π-N amplitude, (2) fully covariant kinematics, (3) use of invariant amplitudes which do not contain kinematic singularities, and (4) a finite-range off-shell pion-nucleon model which contains the nucleon pole term.The effect of the delta-nucleus interaction is included via the mean spectral-energy approximation. It is demonstrated that this produces a convergent perturbation theory in which the Pauli corrections (here treated as a second-order term) cancel remarkably against the pion true absorption terms. Parameter-free results, including the delta-nucleus shell-model potential, Pauli corrections, pion true absorption, and short-range correlations are presented.Pion-scattering measurements, in combination with phenomenological descriptions [1] of the propagation of the pion and the delta in the nuclear medium, have proved useful 1

We investigate theoretical approaches to pion-nucleus elastic scattering at high energies (300 ≤ T π ≤ 1 GeV). A "model-exact" calculation of the lowest-order microscopic optical model, carried out in momentum space and including the full Fermi averaging integration, a realistic off-shell pion-nucleon scattering amplitude and fully covariant kinematics, is used to calibrate a much simpler theory. The simpler theory utilizes a local optical potential with an eikonal propagator and includes the Coulomb interaction and the first Wallace correction, both of which are found to be important. Comparisons of differential cross sections out to beyond the second minimum are made for light and heavy nuclei. Particularly for nuclei as heavy as 1 40 Ca, the eikonal theory is found to be an excellent approximation to the full theory. PACS number(s): 25.80. Ek, 24.10.Eq, 24.10.Jv