A New Method for the Determination of the Real Part of the Hadron Elastic Scattering Amplitude at Small Angles and High Energies

A new method for the determination of the real part of the elastic scattering amplitude is examined for high energy proton-proton elastic scattering at small momentum transfer. This method allows us to decrease the number of model assumptions, to obtain the real part in a narrow region of momentum transfer and to test different models. The real part is computed at a given point t_min near t=0 from the known Coulomb amplitude. Hence one obtains an important constraint on the real part of the forward scattering amplitude and therefore on the rho-parameter (measuring the ratio of the real to imaginary part of the scattering amplitude at t=0), which can be tested at LHC.Comment: 10 pages and 5 figures. Final published form in Physics Letters

Saturation effects in pp scattering in the impact-parameter representation

The impact of unitarity is considered in different approaches to saturation in impact-parameter space. The energy and momentum-transfer dependence of the total and differential cross sections and of the ratio of the real to imaginary parts of the scattering amplitude are obtained in a model that includes soft and hard pomeron contributions, coupled to hadrons via the electromagnetic form factor. It is shown that the hard pomeron may significantly contribute to soft physics at the LHC. A similar conclusion can also be reached in the framework of non-linear approaches to unitarisation of the BFKL pomeron.Comment: 3 pages, 1 figure, uses espcrc2.sty. Contribution to ``Diffraction 2004'', International Workshop on Diffraction in High-Energy Physics, Cala Gonone, Sardinia, September 18-23, 200

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

A Review of the hard pomeron in soft diffraction

We review the evidence for the presence of a hard singularity in soft forward amplitudes, and give an estimate of its trajectory and couplings

GPDs of the Nucleons and Elastic Scattering at LHC Energies

Taking into account the electromagnetic and gravitational form factors, calculated from a new set of $t$-dependent GPDs, a new model including the soft and hard pomerons is build. In the framework of this model the ualitative description of all existing experimental data at $\sqrt{s} \leq 52.8$ GeV, including the Coulomb range and large momentum transfers, is obtained with only 4 free parameters. Predictions for LHC energies are made