Isobar configurations: ΔN correlations versus the independent particle model

Abstract

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 ∆N correlation model and the quasifree pion photoproduction model. The considered models differ in their descriptions of the nucleus states. The ∆N correlation model takes into account the dynamic correlations of the nucleon and isobar formed in the virtual transition N N → ∆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 reactionsIt 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 ∆N correlation model for the (γ, πN ) and (γ, πN N ) reactions with the 16 O(γ, π − p) reaction data measured at BNL. Our results give support to the ∆N correlation model.

Isobar Configurations in the Ground State of Nuclei. Effective Polarization of an Isobar

“…Polarization observables contain the dependence of the cross section of the interaction on the relative orientation of the spins and momenta of the particles. We will consider the polarization properties of the interaction of a photon with a virtual  -isobar, manifested in the nuclear reaction 16 15 , in , l s   ), we write expression (1), summed over the spin states p f of the proton, in the following way [14]:…”