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

Abstract

We compare total reaction cross sections found in proton and composite-projectile ($d$ and $\ensuremath{\alpha}$) 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 ${\ensuremath{\sigma}}_{R}$ values is found to be as large as or larger than for protons. A simple semiclassical analysis suggests that, at ${E}_{\mathrm{c}.\mathrm{m}.}/\mathrm{nucleon}$ of approximately 250 MeV, composite-projectile collisions are, in effect, more transparent than proton collisions with the same target nucleus.