In this paper an introduction to the physics of deep-inelastic scattering is given together with an account of some of the most recent results on the proton structure obtained in electron– and positron–proton collisions at the HERA collider.

The multichannel scattering theory is applied to the (2,2) sector of the (non-static) Lee model. Rigorous expressions for the transit ion amplitudes for two-fragments channels are derived. These expressions contain al l effects of off-shell renormalizat ion in a complete and consistent way. W i t h suitable identification of the elementary fields of the model the reactions considered correspond...