[en] We measured simultaneously pp elastic and quasi-elastic (p, 2p) scattering in hydro- gen, deuterium and carbon at incoming momenta of 5.9 and 7.5 GeV/c and center- of-mass scattering angles in the range 83.7 degrees to 90 degrees. We extracted the cross section ratios of quasi-elastic ¹²C(p, 2p) to elastic ¹H(p, 2p) (C/H) and quasi-elastic D(p, 2p) to elastic ¹H(p, 2p) (D/H). The experiment was performed at the Brookhaven National Laboratory AGS accelerator using the EVA detector (experiment E850). For a detailed description of the experiment and the analysis. We determined that at incoming momentum of 5.9 GeV/c, the C/H ratio increases by a factor of 2 from θ_cm = 89 degrees to θ_cm 85 degrees, while at 7.5 GeV/c it is consistent with being flat. Further, at θ_cm = 89 degrees the C/H ratio increases from 5.9 GeV/c to 7.5 GeV/c by more than 50%, while for lower θ_cm the incoming momentum dependence is consistent with being flat. The rise of the C/H ratio with incoming momentum is similar to that observed in the previous measurement of the C/H ratio at θ_cm near 90 degrees. The dependence of the C/H ratio on θ_cm, was observed in our experiment for the first time. The D/H ratio does not depend on incoming momentum and θ_cm Its absolute value is consistent with unity. The D/H ratio was measured in our experiment for the first time. The ratios discussed above are directly related to the nuclear transparency of ¹²C and D. Nuclear transparency is a measure of the initial and final state interactions that the incoming and outgoing protons undergo before and after the main (p, 2p) reaction. The standard approach to nuclear transparency does not depend on the incoming momentum nor on θ_cm in contradiction to the variation of the C/H ratio that we have observed. The incoming momentum dependence of the C/H ratio that we measured is similar to those of the inverse scaled pp differential cross section (s¹⁰(dσ/dt))^-1 where s and t are the Mandelstam variables, and the inverse of the pp spin-spin correlation parameter (A_nn)^-1. The θ_cm dependence of the C/H ratio is similar to that of (A_nn)^-l. On the basis of some models, these similarities may suggest that our new experimental results indicate that the C nucleus filters away non-perturbative QCD components of the pp scattering amplitude