Nuclear transparency

Nuclear transparency is the ratio of cross-sections for exclusive processes from the nuclei to those of the nucleons.

If the nuclear cross-section is denoted as $\sigma_N$ and free nucleon cross-section as $\sigma_0$ then nuclear transparency can be defined as
$T= \sigma_N/A\sigma_0$ , where $\sigma_N$ can be parameterized in terms of $\sigma_0$ as $\sigma_N =A^\alpha \sigma_0$ .

Therefore, transparency can be expressed as $T= A^{\alpha -1}$ .
Here nucleon cross-section can be thought of as hydrogen cross-section and nuclei cross-section can be as for other targets.