Oscillating Color Transparency in $\pi A\to \pi p (A-1)$ and $\gamma A\to \pi N (A-1)$

Abstract

The energy dependence of $90^o$ $cm$ fixed angle scattering of $\pi p \to \pi' p'$ and $\gamma p\to \pi^+ n$ at large momentum transfer are found to be well described in terms of interfering short and long distance amplitudes with dynamical phases induced by Sudakov effects. We calculate the color transparency ratio for the corresponding processes in nuclear environments $\pi A\to \pi'p(A-1)$ and $\gamma A\to \pi N (A-1)$ taking nuclear filtering into account. A prediction that the transparency ratio for these reactions will oscillate with energy provides an important test of the Sudakov phase shift and nuclear filtering hypothesis which is testable in upcoming experiments.