PUB - Publikationen an der Universität Bielefeld

Employing the representation of the experimental data on deep inelastic electron-proton scattering (DIS) in the color-dipole picture (CDP), we determine the gluon distribution of the proton at small Bjorken xxx. At sufficiently large momentum transfer, Q2Q^2Q2, the extracted gluon distribution fulfills the evolution equation for the proton structure function. For low values of Q2Q^2Q2, e.g. for Q2=1.9GeV2Q^2 = 1.9 {\rm GeV}^2Q2=1.9GeV2, the evolution equation for the proton structure function requires a strong modification of predicted magnitude. The standard procedure of adopting a low-Q2Q^2Q2 input scale for the extraction of the gluon density is highly questionable. Without modification at low Q2Q^2Q2, the evolution is inconsistent with the required low-Q2Q^2Q2 decrease of the longitudinal structure function with decreasing momentum transfer Q2Q^2Q2.