Factorization of the dependence in electroproduction of vector mesons

Abstract

In a framework for nonperturbative QCD calculation of high energy processes, the amplitudes for photo-and electroproduction of vector mesons are written as integrals of the overlap product of photon and vector meson wave functions, multiplied by the amplitude for the scattering of qq dipole pairs off the proton. For sizes of the overlap functions that are smaller than the typical ranges of the interaction of the dipoles with the proton, the amplitudes factorize in the form of integrals, here called overlap strengths, formed only with the overlap of the wave functions times the square of the dipole separation. The integration is extended over the light front coordinates describing the qq dipoles. With this result, the overlap strengths contain all Q 2 dependence of the observables. We show the importance of this factorization in the description of the experimental data for all S-wave vector mesons.

Nonperturbative and perturbative aspects of photo- and electroproduction of vector mesons

“…As in the case of ρ electroproduction, there is indication that the data cannot be well represented by a single expression of the form of Eq. (18). The data are poorer here than in the ρ case, and it is important to investigate the possibility of a transition region in an intermediate Q 2 range below 10 GeV 2 in which the normalization and the power change values rather rapidly.…”

“…The data are from the Zeus[35,36] and H1[37] collaborations. The solid line represents our theoretical calculation using the BL wave function.The dotted curve is a pure fit to the experimental points of the form given by Eq (18)…”

Vector meson electroproduction: recent results and universality

“…New measurements in the p elastic case [2], and preliminary information from HI collaboration [3] on -fp -^ pp and "fp ^ p(j> aie now available, including t distribution, polarization matrix elements and Q^ and W dependencies. It is important to study these data, since the broader wave functions of the light vector mesons impose more rigorous tests on the dynamical mechanisms [4] .…”

Universality in the Electroproduction of Vector Mesons

“…A Fourier transform leads from the impact parameter picture in the transverse plane to the momentum transfer description. After integration over the geometric weighted distribution of loops, the correct Q 2 dependence and normalization of cross sections emerge [20] , which turns…”