Evidence for Transparency in Medium-Energy Composite-Projectile—Nucleus Collisions

We compare total reaction cross sections found in proton and composite-projectile ($d$ and $\alpha$) collisions with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ target nuclei at incident energies between 5 and 600 MeV/nucleon. The energy dependence of the composite-projectile ${\sigma }_R$ values is found to be as large as or larger than for protons. A simple semiclassical analysis suggests that, at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}/\mathrm{nucleon}$ of approximately 250 MeV, composite-projectile collisions are, in effect, more transparent than proton collisions with the same target nucleus.