Evidence for the Onset of Color Transparency in $\ddot{I}{}^0$ Electroproduction off Nuclei

Abstract

We have measured the nuclear transparency of the incoherent diffractive $A(e,e^{\prime }\ddot{I}{}^0)$ process in ${}^{12}$C and ${}^{56}$Fe targets relative to ${}^2$H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced $\ddot{I}{}^0$'s on a nucleus relative to deuterium, which is sensitive to $\ddot{I}A$ 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 ${}^{12}$C and ${}^{56}$Fe showed no $l_c$ dependence, a significant $Q^2$ dependence was measured, which is consistent with calculations that included the color transparency effects.

6 pages and 4 figures