Measurement of nuclear transparency for the A(e,e′π+) reaction

We have measured the nuclear transparency of the A(e,e(')pi(+)) process in H-2, C-12, Al-27, Cu-63, and Au-197 targets. These measurements were performed at the Jefferson Laboratory over a four momentum transfer squared range Q(2) = 1.1 to 4.7 (GeV/c)(2). The nuclear transparency was extracted as the super-ratio of (sigma(A)/sigma(H)) from data to a model of pion-electroproduction from nuclei without pi-N final-state interactions. The Q(2) and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.