QCD and the Hadronic Final State in Deep Inelastic Scattering at HERA

TL;DR

This paper reviews measurements of the hadronic final state in deep inelastic scattering at HERA, highlighting tests of QCD, determinations of the strong coupling, and evidence for non-DGLAP evolution and instanton effects.

Contribution

It provides a comprehensive overview of experimental results related to QCD in deep inelastic scattering, including new insights into gluon density and non-standard evolution mechanisms.

Findings

Determined the gluon density using jet rates and charm production.

Observed indications of non-DGLAP evolution at small x, possibly explained by BFKL.

Presented first search results for QCD instanton effects.

Abstract

The measurements of the hadronic final state in deep inelastic scattering at HERA are reviewed and discussed in the context of QCD. Covered are the general event properties in terms of energy flows, charged particle production, and charm and strangeness production. Quark fragmentation properties are studied in the Breit frame. Event shape measurements allow "power corrections" to be applied and the strong coupling alpha_s to be extracted. Other alpha_s measurements are based on dijet rates. Jet rates as well as charm production have been used to determine the gluon density in the proton. Indications have been found in the hadronic final state for unconventional, non-DGLAP evolution at small x, which could be explained with BFKL evolution. Signatures for QCD instanton effects are discussed and first search results are presented.