Diffractive photo- and leptoproduction of vector mesons $\rho$, ${\rho }^{\prime }$ and ${\rho }^{\prime \prime }$

Abstract

We calculate diffractive photo- and leptoproduction of $\rho$-, ${\rho }^{\prime }$- and ${\rho }^{\prime \prime }$-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 ${\rho }^{\prime }$- and ${\rho }^{\prime \prime }$-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.

Comments: 28 pages, LaTeX2e, 16 ps/eps figures included, accepted for publication in Eur.Phys.J.C; revised v2: one reference added, one typo corrected