Diffractive photo- and leptoproduction of vector mesons $ρ$, $ρ'$ and $ρ''$

Abstract

We calculate diffractive photo- and leptoproduction of $ρ$-, $ρ'$- and $ρ''$-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 $ρ'$- and $ρ''$-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 $π^+π^-$-invariant mass for photoproduction and $e^+e^-$-annihilation.