The Total Cross Section at the LHC: Models and Experimental Consequences

I review the predictions of the total cross section for many models, and point out that some of them lead to the conclusion that the standard experimental analysis may lead to systematic errors much larger than expected.Comment: Contribution to the 13th International Conference on Elastic & Diffractive Scattering (13th "Blois Workshop"), CERN, 29th June - 3rd July 200

A Review of the Soft Pomeron

Soft pomeron fits reproduce all zero-Q2 data for light quarks, but run into problems at HERA for heavy mesons and for high Q2, and at the Tevatron for W diffractive production. I review the basic properties of the soft pomeron, and outline the possibilities which have been considered to account for the new data.Comment: Latex document, 8 pages, no figures. Invited talk at the International Europhysics Conference on High Energy Physics (HEP 95), 27 Jul - 2 Aug 1995 , Brussels, Belgiu

Unitarisation of the hard pomeron and black-disk limit at the LHC

Recent models of soft diffraction include a hard pomeron pole besides the usual soft term. Such models violate the black-disk limit around Tevatron energies, so that they need to be supplemented by a unitarisation scheme. Several such schemes are considered in this letter, where we show that they lead to a large uncertainty at the LHC. We also examine the impact of unitarisation on various small-t observables, the slope in t of the elastic cross section, or the ratio of the real to imaginary parts of the scattering amplitude, leading to the conclusion that the existence of a hard pomeron in soft scattering may be confirmed by LHC data.Comment: 15 pages, 12 figures, late

Perturbative QCD Corrections to the Soft Pomeron

We study the interface between soft and hard QCD at high energy and small momentum transfer. At LHC and SSC energies, we find that a cutoff BFKL equation leads one to expect a measurable perturbative component in traditionally soft processes. We show that the total cross section could become as large as 175 mb (122 mb) and the rho parameter 0.40 (0.25) at the SSC (LHC).Comment: 10 pages, McGill/92--2

An Analysis of the New LHC Data through the Dispersion Relations

We analyse the tension between the (indirect) measurements of the total cross section, and show the impact of various assumptions on the extraction of the parameters from the elastic scattering amplitude, with a special attention to the total cross section. In particular, the determination of the phase of the elastic scattering amplitude will play an important role, and we shall study it via dispersion relations. We shall also examine the origin of the dependence on momentum transfer of the slopes of the different parts of the scattering amplitude in different models. We shall also give the results of another similar analysis based on a Regge-trajectory approach for the hadron scattering amplitude.Comment: 5 page

Comparison of different non-linear equations and corresponding unitarization schemes

Different forms of non-linear equations which mimic parton saturation in the non-perturbative regime are examined. These equations lead to corresponding unitarization schemes in the impact parameter representation of the hadron scattering amplitude. It is shown how specific properties of the non-linear equations reflect different features of the diffraction processes.Comment: 7 pages, 5 figures, needs PoS.cls and PoSlogo, contribution to the proceedings of the International Workshop on Diffraction in High-Energy Physics "DIFFRACTION 2006", Adamantas, Milos island, Greece, September 5 - 10, 200

Long-range potential and the fine structure of the diffraction peak

The possibility of oscillations in the differential elastic cross section of hadron scattering at small momentum transfer is studied. It is shown that string-like quark potentials at large distances can lead to such small oscillations, and an analysis of the experimental data at small $|t|$ allows the determination of the parameters of the potential.Comment: 6 pages, 6 figures, Talk presented at the International Workshop on Diffraction in High-Energy Physics, Otranto (Lecce, Italy), September 10-15, 201