Nuclear coherent π0 photoproduction with charge-exchange and spin-flip rescattering

In this work, we present an updated model for nuclear π⁰ photoproduction, which incorporates pion second-order rescattering on intermediate excited nuclear states. Our approach is based on the distorted wave impulse approximation in momentum space. The many-body medium effects are incorporated in the complex effective Δ self-energy, employing the results of the recently developed second-order pion-nucleus scattering potential. The experimental data for ¹²C and ⁴⁰Ca are successfully described without the need to fit the model parameters of the photoproduction amplitude as a result of incorporating the second-order part of the nuclear photoproduction potential, which involves intermediate nucleon spin-flip and charge exchange.