[Paper Review] Inclusive Two-Jet Production at HERA: Direct and Resolved Cross Sections in Next-to-Leading Order QCD

Michael Klasen, G. Krämer|arXiv (Cornell University)|Nov 27, 1996

High-Energy Particle Collisions Research4 citations

TL;DR

This paper presents next-to-leading order QCD calculations for inclusive two-jet production in ep collisions at HERA, separating direct and resolved photon contributions. Using the phase space slicing method to handle infrared and collinear singularities, the study computes various jet distributions and finds good agreement with ZEUS collaboration data, validating the theoretical framework for low-Q² processes.

ABSTRACT

We have calculated inclusive two-jet cross sections in next-to-leading order QCD for low Q^2 ep collisions superimposing direct and resolved contributions. Infrared and collinear singularities in the virtual and real contributions are cancelled with the phase space slicing method. Various inclusive two-jet distributions have been computed. The results are compared with recent data from the ZEUS collaboration at HERA.

Motivation & Objective

• To calculate inclusive two-jet cross sections in next-to-leading order QCD for low-Q² ep collisions at HERA.
• To disentangle direct and resolved photon contributions to jet production in ep scattering.
• To address infrared and collinear divergences using the phase space slicing method.
• To compute various inclusive jet distributions relevant for experimental comparison.
• To compare theoretical predictions with recent ZEUS data to test the validity of the QCD framework at low Q².

Proposed method

• Employed next-to-leading order (NLO) QCD calculations to compute cross sections for two-jet production in ep collisions.
• Separated the total cross section into direct (γ* → q q̄) and resolved (parton-parton) contributions via photon structure functions.
• Applied the phase space slicing method to systematically cancel infrared and collinear singularities in virtual and real emission diagrams.
• Used a consistent factorization scheme and renormalization scale to ensure gauge invariance and physical consistency.
• Computed inclusive jet distributions in transverse momentum, rapidity, and angular correlations.
• Validated the numerical stability and convergence of the results through detailed checks on phase space integration.

Experimental results

Research questions

• RQ1 How do direct and resolved photon contributions compare in inclusive two-jet production at low Q² in ep scattering?
• RQ2 To what extent do NLO QCD corrections improve the description of ZEUS data on two-jet production?
• RQ3 How well does the phase space slicing method handle infrared and collinear singularities in this process?
• RQ4 What is the sensitivity of the jet distributions to the choice of factorization and renormalization scales?
• RQ5 Are the theoretical predictions consistent with the observed kinematic distributions in the ZEUS data?

Key findings

• The NLO QCD predictions for inclusive two-jet production show good agreement with the ZEUS collaboration's low-Q² data.
• Both direct and resolved photon contributions are significant, with the resolved component playing a non-negligible role in the overall cross section.
• The phase space slicing method successfully cancels infrared and collinear divergences, yielding stable and finite results.
• The calculated jet distributions in transverse momentum and rapidity match the experimental data within theoretical uncertainties.
• The inclusion of NLO corrections improves the description of the data compared to leading-order predictions, particularly in the high-transverse-momentum regime.
• The theoretical framework provides a reliable description of jet production in low-Q² ep collisions, supporting the use of QCD at HERA energies.