Pion- und photoninduzierte Reaktionen an Kernen im $\Delta$-Resonanzbereich

In the present work pion- and photoinduced nuclear reactions in the $\Delta$ resonance energy region are studied. In particular, we investigate the propagation of the $\Delta$ inside the nucleus. It is found that the propagation of the $\Delta$ in the medium can be interpreted in terms of a coherent pion wave. The behaviour of the $\Delta$ resonance in the nucleus is studied vy means of various inclusive and exclusive processes. These different reactions give complementary information on the properties of the $\Delta$ in nuclei. Elastic pion-scattering, coherent pion photoproduction and elastic Compton-scattering allow us to study the spin-longitudinal and spin-transverse channels, their their mixing and their influence on the coherent medium effect. The quasi-free decay reaction and the 2-nucleon.knockout reaction give information on the damping mechanisms of the coherent pion wave inside the nucleus. Additionally, they allow us to study the momentum distribution of the nucleons and the $\Delta$ in the nucleus. Our model describes consistently the pion- and potoinduced reactions as well as charge exchange reactions. [...