Pion-nucleus scattering at around the DELTA (1232) resonance

The pion-nucleus scattering around 200 MeV and just above 1200 MeV is dominated by strong, broad DELTA (3,3) and weak resonances in the pi sup+-N interaction. The interaction to a first approximation can be described as diffraction process. Since it is well known that the strength of the pi sup + N and pi sup - N interactions are quite different from each other at the resonances, the analyses of differential cross section for pi sup + N and pi sup - N elastic scattering data in the region of low-lying pion-nucleus resonances will be a good test of different strengths. In the present work we analyze pions scattering from nuclei sup 9 Be, sup 2 sup 8 Si, sup 5 sup 8 Ni, sup 8 sup 9 Y and sup 2 sup 0 sup 8 Pb at incident pion energies between 50 and 291 MeV within the framework of the three parameter version of the Strong Absorption Model of Frahn and Venter. All the oscillations in the elastic scattering experimental data and for the experimental angular distribution leading to 2 sup + and 3 sup - collective states could be well reproduced by the model. The best fit parameter values for T, DELTA and mu are determined. They are respectively the cut-off angular momentum, rounding parameter and the real nuclear phase shift parameters of the model. The interaction radius 'R', the surface diffuseness 'd' and the reaction cross-section sigma sub r have been determined from the derived parameter values. The standard nuclear radius r sub 0 and the surface diffuseness 'd' are fairly constant. The deformation parameters beta sub L have been determined from the normalization constant of the theory to the experiment without making any change in the elastic scattering parameters. The beta sub 2 and beta sub 3 values so extracted are in good agreement with other works. It is observed that there is hardly any difference between the values of beta sub 2 (pi sup +) and beta sub 2 (pi sup -) and that between beta sub 3 (pi sup +) and beta sub 3 (pi sup -) values.