Exclusive production of vector mesons ρ, ρ' and ρ'' by real and virtual photons

We present a non-perturbative QCD calculation of high-energy diffractive photo- and leptoproduction of vector mesons π, π' and π'' on a nucleon. The initial photon splits up in a qq-bar-dipole and transforms into a vector meson by scattering on the quark-diquark nucleon. The dipole-dipole scattering amplitude is provided by the non-perturbative model of the stochastic QCD vacuum, the wave functions result from considerations on the light-cone. We assume the physical ρ'- and π''-states to be mixed states of an active 2S-excitation and a rest whose coupling to the photon is suppressed. We obtain good agreement with the experimental data and get an understanding of the markedly different spectrum in the π+π--invariant mass for photoproduction and e+e--annihilation