612 research outputs found
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
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
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
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