Pion-nucleus elastic scattering at intermediate energies

Dynamical modifications of the pion-nucleus optical potential due to binding effects on the target nucleons are calculated for pions of energies in the range 120-600 MeV. Calculations are performed using an independent particle model for the nucleus; however, a prescription for incorporation of the Pauli principle is given and its effects are studied. Resulting corrections to the potential are of the order of 50-100% near the (3, 3) resonance and fall to negligible values at energies less than 120 MeV and greater than 450 MeV. Our correction is such as to increase the nuclear opacity. Pion-nucleus total cross sections and angular distributions are modified by binding effects by 10-20%. Comparison with $\pi$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ total cross section data shows that our theory reproduces well the energy dependence of the correction required to reconcile theory and experiment, and produces about 50% of the necessary increase in the magnitude of the theoretical cross section.