SMALL-X PHYSICS IN DEEP-INELASTIC LEPTON-HADRON SCATTERING

This article reviews the physics of deep-inelastic lepton-hadron processes in the region of small x, where x is the Bjorken scaling variable. The theoretical concepts concerning the Regge limit of deep-inelastic scattering are summarized and recent theoretical results on the small-x limit of parton distributions in perturbative QCD are discussed. Presently available experimental data on the free- and bound-nucleon structure functions at small x are reviewed in detail and their theoretical interpretations (including the low-x, low-Q2 region) are discussed. QCD predictions are given for the deep-inelastic scattering structure functions F2 and F(L) in the small-x (10(-5) < x < 10(-2)) and moderately large-Q2 region relevant for HERA (Q2 is similar to 10 GeV2).