Incoherent Production of Charmonia off Nuclei As a Good Tool for Study of Color Transparency

Abstract

Within a light-cone QCD formalism which incorporates color transparency (CT), coherence length (CL) effects and gluon shadowing (GS) we study electroproduction of charmonia off nuclei. In contrast to production of light vector mesons (rho^0, phi^0) when at small and medium energies CT and the onset of CL effects are not easily separated, in production of charmonia CT effects dominate. We found rather large CT effects in the range of Q^2 < 20 GeV^2. They are stronger at low than at high energies and can be easily identified by the planned future experiments. Our parameter-free calculations explain well the NMC data for variation with photon energy of the Sn/C ratio of nuclear transparencies. We provide predictions for incoherent and coherent production of charmonia for future measurements.