Anomalous A-dependence of diffractive leptoproduction of radial excitation $\rho'(2S)$

Abstract

We predict a strikingly different $A$ and $Q^{2}$ dependence of quasielastic leptoproduction of the $\rho^{0}(1S)$-meson and its radial excitation $\rho '(2S)$ on nuclei. Whereas for the $\rho^{0}$ production nuclear transparency $T_{A}$ decreases monotonically with $A$, for the $\rho'$ 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 $\rho ' /\rho^{0}$ cross section ratio makes nuclear targets the $\rho '$-factory. The origin of the anomalous $A$-dependence is in the interplay of color transparency effects with the nodal structure of the $\rho '$ wave function. The predicted effects take place at moderate $Q^{2}\lsim (2-3)$GeV$^{2}$, which can be explored in high statistics experiments at CEBAF.