Proton-proton forward scattering at the LHC

M Broilo,D.A Fagundes,E.G.S Luna,M.J Menon

doi:10.1016/j.physletb.2019.135047

Abstract

Recently the TOTEM experiment at the LHC has released measurements at s=13 TeV of the proton-proton total cross section, σtot, and the ratio of the real to imaginary parts of the forward elastic amplitude, ρ. Since then an intense debate on the C-parity asymptotic nature of the scattering amplitude was initiated. We examine the proton-proton and the antiproton-proton forward data above 10 GeV in the context of an eikonal QCD-based model, where nonperturbative effects are readily included via a QCD effective charge. We show that, despite an overall satisfactory description of the forward data is obtained by a model in which the scattering amplitude is dominated by only crossing-even elastic terms, there is evidence that the introduction of a crossing-odd term may improve the agreement with the measurements of ρ at s=13 TeV. In the Regge language the dominant even(odd)-under-crossing object is the so called Pomeron (Odderon).

Highlights

The rise of the total cross section with energy in hadron-hadron collisions was theoretically predicted many years ago [1]
In accordance with very general predictions based on axiomatic field theory, all models using this QCD-based formalism have assumed over the years that at high energies the scattering amplitude is dominated by only a single crossing-even elastic amplitude
The nonperturbative dynamics of the QCD is treated in the context of a well-established infrared effective charge dependent on the dynamical gluon mass. Such a model, involving only even-under-crossing amplitudes dominant at very high energies, provides a satisfactory global description of σtot and ρ data over a wide range of energies√, and the larger ρ value predicted by the model at s = 13 TeV suggests that a crossing-odd elastic term may play an important role in the soft and semihard interactions

Summary

Introduction

The rise of the total cross section with energy in hadron-hadron collisions was theoretically predicted many years ago [1]. In this picture the high-energy behavior of the cross sections is driven mainly by semihard processes involving gluons, since they give the dominant contribution at small x [5,6,7].

Results

Conclusion