ar X iv : h ep - p h / 07 02 27 2 v 2 1 M ar 2 00 7 Color Transparency at Low Energies : Predictions for JLAB

The study of color transparency (CT) in elastic electroproduction of vector mesons off nuclei encounters the problem of the onset of coherence length (CL) effects. The problem of CT-CL separation arises especially at medium energies, corresponding to HERMES experiment, when the coherence length is of the order of the nuclear radius RA. Only at asymptotic large energies, corresponding to large CL, lc ≫ RA, the CT-CL mixing can be eliminated. On the other hand, the net CT effects can be studied in the kinematic range accessible by the CLAS experiment, since in this case the CL is much smaller than the nuclear radius. Using light-cone quantum chromodynamics (QCD) dipole formalism we investigate manifestations of CT effects in electroproduction of vector mesons. Motivated by expected data from the CLAS experiment at JLab, we predict the A andQ dependence of nuclear transparency for ρ mesons produced incoherently off nuclei. We demonstrate that in the CLAS kinematic region the CL effects are weak enough to keep the photon energy at such values as to obtain maximal photon virtualities keeping optimal statistics of the data. This has a clear advantage in comparison with a standard investigation of net CT effects fixing CL.