Evidence for transparency in medium-energy composite-projectile nucleus collisions

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