Anomalous A-dependence of diffractive leptoproduction of radial excitation ${\rho }^{\prime }(2S)$

Abstract

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

Comments: 10 pages, 4 figures (to be requested), Juelich preprint KFA-IKP(Th)-1994-18