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In this work, we present an updated model for nuclear 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 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 nuclear photoproduction potential, which involves intermediate nucleon spin-flip and charge exchange.
Tsaran et al. (Wed,) studied this question.