th / 9 30 70 08 v 1 7 J ul 1 99 3 Pion - nucleus reactions in a microscopic transport model ∗

We analyse pion–nucleus reactions in a microscopic transport model of the BUU type, which propagates nucleons, pions, deltas and N (1440)-resonances explicitly in space and time. In particular we examine pion absorption and inelastic scattering cross sections for pion kinetic energies T π = 85 − 315M eV and various target masses. In general, the mass–dependence of the experimental data is well described for energies up to the ∆–resonance (≈ 160M eV) while the absorption cross sections are somewhat overestimated for the higher energies. In addition we study the possible dynamical effects of delta– and pion–potentials in the medium on various observables as well as alternative models for the in-medium ∆-width.