DEEP-INELASTIC ONIUM SCATTERING

Using the colour dipole approach of the QCD perturbative (BFKL) Pomero n exchange in onium-onium scattering, we compute the cross section for small but hierarchically different onium sizes. A specific term depen dent on the size-ratio is generated. In deep inelastic onium scatterin g it appears as a scaling-violation contribution to the quark structur e function near the BFKL singularity. We find that the extension of th e formalism for deep inelastic onium scattering to the proton structur e function provides a remarkably good 3-parameter fit to HERA data at small x with a simple physical interpretation in terms of the dipole f ormulation.