The final- (or initial-) state interactions of pions participating in reactions with a complex nucleus are usually treated in distorted-wave impulse approximation with optical model wave functions. We improve this approximation by using an "effective pion field" which takes into account the hard-core nuclear correlations. This is illustrated here by the example of charged pion photoproduction from a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\gamma , {\pi }^{-}){}_{}{}^{12}{}_{}{}^{}\mathrm{N}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$, calculated $\sigma \left(\Omega \right)$, distorted pion wave, included effects of nucleon-nucleon correlations.

• Received 10 June 1974

DOI:https://doi.org/10.1103/PhysRevC.12.1586