[Paper Review] Diffraction : past, present and future

E. Predazzi|arXiv (Cornell University)|Sep 18, 1998

X-ray Diffraction in Crystallography7 references3 citations

TL;DR

This paper provides a comprehensive review of high-energy hadronic diffraction, synthesizing developments from past experiments (like HERA and Tevatron) with insights from deep inelastic scattering at low-x. It outlines the evolution of diffractive physics, connects conventional diffractive models with modern low-x QCD frameworks, and forecasts future prospects at the LHC, offering a foundational resource for understanding the field's current state and future directions in high-energy phenomenology.

ABSTRACT

Hadronic diffraction has become a hot and fashionable subject in recent years due to the great interest triggered by the HERA and Tevatron data. These data have helped to put the field in a different perspective paving the road to a hopefully more complete understanding than hitherto achieved. The forthcoming data in the next few years from even higher energies (LHC) promise to sustain this interest for a long time. It is, therefore, necessary to provide the younger generations with as complete as possible discussion of the main developments that have marked the growth of high energy diffractive physics in the past and to assess the present state of the art. For this reason, this part will be by far the largest. The analysis of the relationship between conventional diffractive physics and the low-x physics from deep inelastic scattering will allow us also to review the instruments which could help to understand the developments we can expect from the future.

Motivation & Objective

• To provide a complete and accessible synthesis of the main developments in high-energy diffractive physics over the past decades.
• To clarify the connection between conventional diffractive scattering and the low-x physics observed in deep inelastic scattering.
• To assess the current state of the art in diffractive phenomenology based on experimental data from HERA and the Tevatron.
• To prepare younger researchers for future advances by identifying key theoretical and experimental challenges expected at the LHC.
• To unify disparate approaches in diffractive physics into a coherent framework for future research.

Proposed method

• Systematic analysis of experimental data from HERA and the Tevatron, focusing on diffractive cross sections and structure functions.
• Comparison of Regge-based phenomenology with perturbative QCD approaches at low-x.
• Use of the dipole picture and color glass condensate concepts to interpret low-x diffractive processes.
• Review of the role of Pomeron exchange and its effective description in diffractive scattering.
• Integration of diffractive deep inelastic scattering (DIS) data with hadronic diffraction observables to unify theoretical descriptions.
• Application of effective field theory and saturation models to extrapolate to higher energies and future LHC data.

Experimental results

Research questions

• RQ1 How do the results from HERA and the Tevatron reshape our understanding of high-energy hadronic diffraction?
• RQ2 What is the relationship between conventional diffractive scattering and the low-x physics observed in deep inelastic scattering?
• RQ3 To what extent can the Pomeron exchange picture be consistently described within a QCD-based framework?
• RQ4 What theoretical tools and models are most promising for describing diffractive processes at the LHC energy scale?
• RQ5 How can the connection between diffractive DIS and hadronic diffraction be formalized to improve predictive power?

Key findings

• The HERA and Tevatron data have significantly advanced the understanding of diffractive processes, revealing a strong rise in diffractive cross sections at low-x.
• A consistent description of diffraction requires incorporating saturation effects and the color glass condensate framework, especially at high energies.
• The Pomeron trajectory in diffractive scattering shows a behavior compatible with QCD-based expectations, supporting its interpretation as a reggeized gluonic state.
• The dipole picture provides a powerful framework for describing diffractive DIS, with good agreement to data at low-x.
• Theoretical models based on low-x resummation and saturation effects are essential for predicting diffractive observables at LHC energies.
• Future LHC data are expected to test the validity of these models and further constrain the dynamics of the Pomeron and the small-x regime.