A theoretical approach to the (π−, γγ) reaction in nuclei

We have studied the π− capture in nuclei leading to two photons, using improved many body methods which have been tested with success in one photon π− radiative capture, μ− capture and ν scattering. The qualitative features of the experimental data are reproduced but there is still some disagreement at small relative photon angles. The reaction is a potential source of information on details of the γγππ vertex where chiral corrections can be relevant. New and more precise experiments are planned which make calculations like the present one relevant and opportune.