Massive Schwinger model within mass perturbation theory

In this article we give a detailed discussion of the mass perturbation theory of the massive Schwinger model. After discussing some general features and briefly reviewing the exact solution of the massless case, we compute the vacuum energy density of the massive model and some related quantities. We derive the Feynman rules of mass perturbation theory and discuss the exact $n$-point functions with the help of the Dyson-Schwinger equations. Further we identify the stable and unstable bound states of the theory and compute some bound-state masses and decay widths. Finally we discuss scattering processes, where the resonances and particle production thresholds of the model are properly taken into account by our methods.