Angular correlations in three-jet events in ep collisions at HERA

TL;DR

This paper investigates three-jet events in ep collisions at HERA, measuring angular correlations to test perturbative QCD and gauge group symmetries, confirming SU(3) predictions and ruling out larger N groups.

Contribution

It provides detailed measurements of angular correlations in three-jet events and compares them with perturbative QCD calculations to study underlying gauge group symmetries.

Findings

Angular correlations are consistent with SU(3) gauge symmetry.

Results disfavor larger N gauge groups like SU(N) for large N.

Measurements agree with perturbative QCD predictions.

Abstract

Three-jet production in deep inelastic ep scattering and photoproduction was investigated with the ZEUS detector at HERA using an integrated luminosity of 127 pb-1. Measurements of differential cross sections are presented as functions of angular correlations between the three jets in the final state and the proton-beam direction. These correlations provide a stringent test of perturbative QCD and show sensitivity to the contributions from different colour configurations. Fixed-order perturbative QCD calculations assuming the values of the colour factors C_F, C_A and T_F as derived from a variety of gauge groups were compared to the measurements to study the underlying gauge group symmetry. The measured angular correlations in the deep inelastic ep scattering and photoproduction regimes are consistent with the admixture of colour configurations as predicted by SU(3) and disfavour other symmetry groups, such as SU(N) in the limit of large N.