49 2 v 1 2 9 A ug 1 99 6 OSU - 96 - 0829 Color Transparency and Color Opacity in Coherent Production of Vector Mesons off Light Nuclei at small x

Color Transparency and Color Opacity in Coherent Production of Vector Mesons off Light Nuclei at small x L. Frankfurt, V. Guzey, W. Koepf, M. Sargsian, M. Strikman (a) Tel Aviv University, Tel Aviv, Israel (b) Pennsylvania State University, University Park, PA, USA (c) Ohio State University, Columbus, OH, USA (d) S.Petersburg Nuclear Physics Institute, Russia (e) Yerevan Physics Institute, Yerevan, Armenia Abstract: Coherent electroproduction of vector mesons off H and He is considered in the kinematics of deep inelastic scattering. Special emphasis is given to the −t ∼ 0.8− 1 GeV region where the cross section is dominated by the interaction of the qq̄ configuration in the γ with two nucleons. These kinematics provide the unique possibilities to study quantitatively in vector meson production the onset of Color Transparency with increasing Q as well as its gradual disappearance at very small x, i.e., perturbative Color Opacity.