Evidence for the onset of color transparency in rho(0) electroproduction off nuclei

We have measured the nuclear transparency of the incoherent diffractive A(e,e' rho(0)) process in C-12 and Fe-56 targets relative to H-2 using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced rho(0,)s on a nucleus relative to deuterium, which is sensitive to rho A interaction, was studied as function of the coherence length (l(c)), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q(2)). While the transparency for both C-12 and Fe-56 showed no lc dependence, a significant Q(2) dependence was measured, which is consistent with calculations that included the color transparency effects. (C) 2012 Elsevier B.V. All rights reserved.