Anomalous A - dependence of diffractive leptoproduction of radial excitation ρ ′ ( 2 S )

A b s t r a c t We predict a strikingly different A and Q 2 dependence of quasielastic leptoproduction of the ρ 0 (1S)-meson and its radial excitation ρ ′ (2S) on nuclei. Whereas for the ρ 0 production nuclear transparency T A decreases monotonically with A, for the ρ ′ nuclear transparency T A can have the counterintuitive nonmonotonic A-dependence, having the minimum for light nuclei, and increasing with A for medium and heavy nuclei. Strong enhancement of the ρ ′ /ρ 0 cross section ratio makes nuclear targets the ρ ′-factory. The origin of the anomalous A-dependence is in the interplay of color transparency effects with the nodal structure of the ρ ′ wave function. The predicted effects take place at moderate Q 2 ∼ < (2 − 3)GeV 2 , which can be explored in high statistics experiments at CEBAF.