Analyses of pi super( plus or minus ) - 12C Elastic Scattering and Reaction Cross-Section Data Below, Atop and Above the Delta -Resonance

The pion-nucleus elastic scattering and reaction cross-section data at incident energies below, atop and above the Delta -resonance are analyzed using the full Klein-Gordon equation using an optical potential. Analytic forms of the potential are determined using the inverse scattering theory in those cases where phase shift analyses were available. The Coulomb effect is incorporated using Stricker's prescription. Both elastic scattering data and the reaction cross sections between 120 and 400 MeV are well reproduced. Both real and imaginary parts of the potential are local. The potential points determined by the inverse scattering theory in the interior region at 230 MeV clearly establish that the real part is repulsive. This remains the case at higher incident energies. The real part turns repulsive above the resonance, whereas the imaginary part reflects the dominance of surface absorption, which is maximum near atop the Delta -resonance and then falling off at higher energies.