Nuclear coherent ${\pi }^0$ photoproduction with charge-exchange and spin-flip rescattering

In this work, we present an updated model for nuclear ${\pi }^0$ 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 $\Delta$ self-energy, employing the results of the recently developed second-order pion-nucleus scattering potential. The experimental data for ${}_{12}C$ and ${}_{40}\mathrm{Ca}$ 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.