Speaker
Description
A phenomenological study of the final combined HERA data on inclusive
deep inelastic scattering (DIS) has been performed. The data are
presented and investigated for a kinematic range extending from
values of the four-momentum transfer of the exchanged boson, $Q^2$,
above $10^4$ GeV$^2$ down to the lowest values observable at HERA of
$Q^2$, and Bjorken $x_{\rm Bj}$ of $Q^2 = 0.045$ GeV$^2$ and
$x_{\rm Bj} = 6 \times 10^{-7}$. The data are well described by fits
based on perturbative quantum chromodynamics (QCD) using collinear
factorisation and evolution of the parton densities encompassed in
the DGLAP formalism down to $Q^2$ of a few GeV$^2$. As $Q^2$
approaches zero, the Regge formalism can describe the data. It is
shown to be appropriate up to $Q^2 \approx 0.5$ GeV$^2$. The data
covering the region between the Regge and the perturbative QCD
regimes are of particular interest. Their features are presented.
