Photopion reactions on deltas preexisting in nuclei
  Reactions A(\gamma, pi^+p) are considered to proceed through the formation of pion-proton pairs on delta constituents in nuclei. We develop the nonrelativistic operator for \Delta^{++}(\gamma, pi^+)p process in an arbitrary frame. The calculated cross section for C12(\gamma, \pi^+p) reaction is compared to the existing experimental data. 
A.Fix, I.Glavanakov, Yu.Krechetov