Interpretation of electron-proton scattering at low Q^2

Abstract

Low-Q^2 photons do not resolve partons in the proton, which gives problems when applying the deep inelastic scattering formalism, such as an unphysical, negative gluon density extracted from data. Considering instead hadronic fluctuations of the photon, we show that the generalised vector meson dominance model (GVDM) gives a good description of the measured cross section at low Q^2, i.e. reproduces F_2(x,Q^2), using only few parameters with essentially known values. Combining GVDM and parton density functions makes it possible to obtain a good description of F_2 data over the whole range of x and Q^2.