Isobar configurations: δN correlations versus the independent particle model

We present a comparative analysis of two models for the A(γ, π. N). B reaction, which take into account the isobar configurations in the ground state of the nuclei: the δ. N correlation model and the quasifree pion photoproduction model. The considered models differ in their descriptions of the nucleus states. The δ. N correlation model takes into account the dynamic correlations of the nucleon and isobar formed in the virtual transition NN→δ. N, 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 δ. N correlation model for the (γ, π. N) and (γ, π. NN) reactions with the O16(γ,π-p) reaction data measured at BNL. Our results give support to the δ. N correlation model.