Energy Dependence of the Delta Resonance: Chiral Dynamics in Action

Abstract. There is an important connection between the low energy theorems of QCD and the energy dependence of the ∆ resonance in π-N scattering, as well as the closely related γ ∗ N → Nπ reaction. The resonance shape is due not only to the strong π-N interaction in the p wave but the small interaction in the s wave; the latter is due to spontaneous chiral symmetry breaking in QCD (i.e. the Nambu-Goldstone nature of the pion). A brief overview of experimental tests of chiral perturbation theory and chiral based models is presented. 1