Chiral-Symmetric Meson-Nucleon Lagrangians

A phenomenological Lagrangian for a theory of nucleons and scalar, pseudoscalar, vector, and axialvector mesons is constructed on the basis of linear representation of chiral $\mathrm{SU}\left(2\right)\mathrm{}\times \mathrm{SU}\left(2\right)\mathrm{}$. The Lagrangian for this extended $\sigma$ model is used for a study of strong interactions of the particles involved and for the derivation of threshold theorems for pion-nucleon and pion-pion scattering, photoproduction of pions on nucleons, and the production of an $s$-wave isoscalar resonance by pions on nucleons.