A model for the γN → ππN reaction

We have studied the γN → ππN reaction using a model wich includes N, Δ(1232), N*(1440) and N*(1520) intermediate baryonic states and the ρ-meson as a intermediate ππ resonance. The model reproduces fairly well experimental cross sections below Eγ=800 MeV and invariant-mass distributions even at higher energies. One of the interesting findings of study is what the γN → N*(1520) → Δπ process is very important and interferes strongly with the dominant Δ-Kroll-Ruderman term to produce the experimental peak of the kross section.