QCD dynamics at low x in ep collisions at HERA

TL;DR

This paper investigates QCD dynamics at low Bjorken x in ep collisions at HERA by measuring forward jet and multijet production, comparing results to various theoretical models, and assessing their predictive accuracy.

Contribution

It provides a comprehensive comparison of experimental data with DGLAP, CCFM, and Colour-Dipole models, highlighting the strengths and limitations of each in describing low x QCD phenomena.

Findings

Fixed-order calculations match data well in most of the phase space.

Leading-order models often fail to describe the data accurately.

The study clarifies the applicability of different QCD models at low x.

Abstract

Forward jet and multijet production has been measured at low Bjorken x at HERA. The measured cross sections and correlations were compared to predictions from DGLAP-based fixed-order calculations. Further comparisons were made to DGLAP-based and CCFM-based leading-order Monte Carlo predictions, as well as to Colour-Dipole model predictions. For the majority of the phase space covered in the HERA kinematic region, fixed-order calculations describe the data well, while the leading-order models provide an inconsistent description of the data.