Recent Developments in Low x Physics

Abstract

The QCD expectations for the behaviour of the deep inelastic scattering structure functions in the region of small values of the Bjorken parameter $x$ are summarized. The Balitzkij, Lipatov, Fadin, Kuraev (BFKL) equation which sums the leading powers of $α_s ln(1/x)$ is described and confronted with the "conventional" formalism based on the leading order QCD evolution equations. The small $x$ behaviour of the spin dependent structure function $g_1$ is also discussed. The dedicated measurements of the hadronic final state in deep inelastic scattering at small $x$ probing the QCD pomeron are described. This includes discussion of the deep inelastic scattering accompanied by forward jets as well as production of forward prompt photons and $π^0$-s. Finally the basic facts concerning the deep inelastic diffraction are briefly summarized.