Diffractive photo- and leptoproduction of vector mesons $\rho$, $\rho'$ and $\rho''$

Abstract

We calculate diffractive photo- and leptoproduction of $\rho$ -, $\rho'$ - and $\rho''$ -mesons. The incoming photon dissociates into a $q\bar{q}$ -dipole which scatters on the nucleon and transforms into a vector meson state. The scattering amplitude is calculated in non-perturbative QCD with the model of the stochastic vacuum. Assuming that the physical $\rho'$ - and $\rho''$ -mesons are mixed states of an active 2S-excitation and some residual hybrid state which cannot be produced diffractively in lowest order QCD, we obtain good agreement with the data, especially the markedly different spectrum in the $\pi^+\pi^-$ -invariant mass for photoproduction and $e^+e^-$ -annihilation.