An integral equation for reaction amplitudes

It is shown that the meson-nucleus inelastic transition or reaction amplitude can be calculated by means of solving a single integral equation. This integral-equation method represents a useful alternative to solving coupled equations in the usual multichannel formalism. The method can be implemented easily for meson-nucleus reactions leading to two-body final states, eliminating the need to use the distorted-wave Born approximation. With the aid of this integral equation, the quality of the extensively employed distorted-wave Born approximation is assessed quantitatively through an example. (author)