Inclusive and diffractive structure functions at small x Original Research Article

In the semiclassical approach, inclusive and diffractive quark and gluon distributions are expressed in terms of correlation functions of Wilson loops. Each Wilson loop integrates the colour field strength in the area between the trajectories of two fast partons penetrating the proton. We introduce a specific model for averaging over the relevant colour field configurations. Within this model, all parton distributions at some low scale Q02 are given in terms of three parameters. Inclusive and diffractive structure functions at higher values of Q2 are determined in a leading-order QCD analysis. In both cases, the evolution is driven by a large gluon distribution. A satisfactory description of the structure functions F2(x, Q2) and F2D(3)(ξ, β, Q2) is obtained. The observed rise of F2D(3) with ξ is parametrized by a non-perturbative logarithmic energy dependence, compatible with unitarity. In our analysis, the observed rise of F2 at small x is largely due to the same effect.