Abstract
With the introduction of a transition potential v( gamma N to pi N) and a gamma N to or from Delta interaction, a Hamiltonian is constructed for gamma , pi , N and Delta as a unified theoretical framework for pi -nucleus reactions and photopion processes. Good fits to pi N scatterings and gamma N to pi N are obtained. Unitarity is included in the theory. It enables the author to obtain consistency in two- and many-body problems for both pi -nucleus and photopion reactions. It is proposed that photopion reactions be used to help determine pi -nucleus interactions.