Phenomenological model for describing pion-pair production on a proton by virtual photons in the energy region of nucleon-resonance excitation

A phenomenological model is developed for describing the production of π + π − pairs on a proton by virtual photons in the energy region of nucleon-resonance excitation.The cross sections are calculated for the channels γp → π −Δ++, γp → π +Δ0, and γp → ρp, which make a dominant contribution to pion-pair production, and the results are compared with available experimental data.The contributions of nucleon resonances to the cross section for the reaction γp → π −Δ++ are predicted within the developed approach