Vector meson leptoproduction and nonperturbative gluon fluctuations in QCD

Abstract

We present a nonperturbative QCD calculation of diffractive vector meson production in virtual photon nucleon scattering at high energy. We use the nonperturbative model of the stochastic QCD vacuum which yields linear confinement and makes specific predictions for the dependence of high-energy scattering cross sections on the hadron size. Using light cone wave functions of the photon and vector mesons, we calculate electroproduction cross sections for ρ, ω, φ and J/ψ. We emphasize the behavior of specific observables such as the ratio of longitudinal to transverse production cross section and the t-dependence of the differential cross section.

Factorization of the dependence in electroproduction of vector mesons

“…Although the observables seem to depend rather weakly on details of the wave function [28], we remark that the shapes of the integrands in the amplitudes (after z integration) are rather broad, so that fixing a value r = r S , whatever the expression for r S , cannot give accurate information on the meson wave function. This remark is particularly meaningful since we show that with our models for the wave functions we obtain good description of the data [1,2,3].…”

“…For convenience we present here some basic formulae developed in our previous work on photo-and electro-production [1,2,3], where details can be found.…”

“…We take the spin structure determined by the vector current, with expressions similar to those of the photon [1,2,20,21]. We thus write Expression 2.11 for the longitudinal wave function, which has been used in many applications, may be modified, with inclusion of an additional term in order to keep consistent correspondence with the gauge invariant expression for the corresponding photon wave function [22].…”

“…The photon couples to the electric charge of the quark-antiquark pair with e f δ ff , where e f =ê f √ 4πα andê f is the quark charge in units of the elementary charge for each flavour. In lowest order perturbation theory, for each polarization λ and flavour f content, we write [1,2,3,10,15,20],…”

“…In previous nonperturbative calculations of photo and electroproduction of J/ψ mesons [1,2,3], where a quantitative description of all experimental data was envisaged, the two-pomeron model of Donnachie and Landshoff [8] was successfully employed. All QCD and hadronic parameters used in our calculation have been defined before [9].…”