Physics at Low x

The QCD expectations concerning the deep inelastic lepton - hadron scattering at low $x$ and their phenomenological implications for HERA are summarised. Theoretical predictions for the structure function $F_2(x,Q^2)$ based on the leading log$1/x$ resummation are presented and compared with the results obtained from the Altarelli-Parisi equations. Theoretical predictions are confronted with the recent data from HERA. The role of studying the final states in deep inelastic scattering for revealing the dynamics at low $x$ is emphasised and some dedicated measurements like deep inelastic plus jet events, transverse energy flow and dijet production in deep inelastic scattering are discussed.Comment: 16 pages, 8 figures, review talk presented at the Workshop "QCD94", 7-13 July 1994, Montpellier, France (to appear in the Proceedings of the Workshop), Krak\'ow INP report N0 1681/PH, hard copies of the figures available on request from the author at [email protected]

Low x saturation at HERA ?

We compare the predictions of two distinct dipole models for inclusive and exclusive diffractive processes. While only one of these dipole models contains perturbative saturation dynamics, we show that the predictions of both models are fully consistent with the available HERA data, indicating no compelling evidence for saturation at present HERA energies.Comment: 8 pages, 4 figures, presented at the 26th Montreal-Rochester-Syracuse-Toronto (MRST) conference held at Concordia University, Montreal, Canada, 12th-14th May 2004. To appear in the proceeding

Low-x evolution of parton densities

It is shown that a Bessel-like behaviour of the structure function F2 at small x, obtained for a flat initial condition in the DGLAP evolution equations, leads to good agreement with the deep inelastic scattering experimental data from HERA.Comment: 8 pages, 3 figures, in Proc. of the third International Workshop on Multiple Partonic Interactions at the LHC (21-25 November 2011, DESY, Hamburg

Saturation in DIS at low x

Saturation at low x appears as an almost unaboidable consequence of the two-gluon excange generic structure.Comment: 3 pages, espcrc2.sty, Presented at Diffraction 2004, Cala Conone, Ital