Isobar configurations: ΔN correlations versus the independent particle model

We present a comparative analysis of two models for the A(γ,πN)B reaction, which take into account the isobar configurations in the ground state of the nuclei: the ΔN correlation model and the quasifree pion photoproduction model. The considered models differ in their descriptions of the nucleus states. The ΔN   correlation model takes into account the dynamic correlations of the nucleon and isobar formed in the virtual transition NN→ΔNNN→ΔN, and in the quasifree pion photoproduction model, isobars and nucleons in the nucleus are considered as independent constituents. The predictions of the models are considered for two reactions O16(γ,π+p)C15 and O16(γ,π−p)O15. It is shown, that the two models predict the differential cross section significantly differing both in absolute values, and in the shape of the angular dependence. We compare the results of the ΔN   correlation model for the (γ,πN) and (γ,πNN) reactions with the O16(γ,π−p) reaction data measured at BNL. Our results give support to the ΔN correlation model.