How to identify color transparency effects in electroproducton of vector mesons off nuclei

Coherent interference of vector mesons electroproduced off nuclei on different nucleons leads to a Q2-dependence in the nuclear transparency at medium energies, which resembles the predictions for the onset of color transparency (CT). We suggest a mapping of the data for different photon energies ν and virtualities Q2 in a way, which eliminates the undesirable Q2-variation and allows to measure a net CT effect. The CT effects are calculated via a multichannel evolution equation for the density matrix, which describes a superposition of different hadronic states produced by a virtual photon and propagating through nuclear matter. The approach is dual to the quark-gluon representation and incorporates effects of CT and of the coherent interference. It solves the color transparency problem for incoherent electroproduction of vector mesons at any photon energy.