Elastic scattering of hadrons

TL;DR

This paper reviews the features and theoretical understanding of elastic scattering of high-energy hadrons, highlighting its contribution to total cross sections, characteristic scattering patterns, and insights into particle structure and dynamics.

Contribution

It provides a comprehensive review of elastic hadron scattering, comparing theoretical models with experimental data and discussing the unitarity condition and scattering amplitude components.

Findings

Elastic scattering accounts for 18-25% of total cross section.

Characteristic scattering features include Gaussian peaks, exponential regimes, and power-law drops.

Interference data yields the real part of the forward scattering amplitude.

Abstract

Colliding high energy hadrons either produce new particles or scatter elastically with their quantum numbers conserved and no other particles produced. We consider the latter case here. Although inelastic processes dominate at high energies, elastic scattering contributes considerably (18-25%) to the total cross section. Its share first decreases and then increases at higher energies. Small-angle scattering prevails at all energies. Some characteristic features are seen that provide informationon the geometrical structure of the colliding particles and the relevant dynamical mechanisms. The steep Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoulders and dips, and then by a power-law drop. Results from various theoretical approaches are compared with experimental data. Phenomenological models claiming to describe this process are reviewed. The unitarity condition predicts an exponential fall for the differential cross section with an additional substructure to occur exactly between the low momentum transfer diffraction cone and a power-law, hard parton scattering regime under high momentum transfer. Data on the interference of the Coulomb and nuclear parts of amplitudes at extremely small angles provide the value of the real part of the forward scattering nuclear amplitude. The real part of the elastic scattering amplitude and the contribution of inelastic processes to the imaginary part of this amplitude (the so-called overlap function) at nonforward transferred momenta are also discussed. Problems related to the scaling behavior of the differential cross section are considered. The power-law regime at highest momentum transfer is briefly described.