Tests of Quantum Chromo Dynamics at e^+e^- Colliders

TL;DR

The paper synthesizes two decades of e+e- annihilation data to test Quantum Chromodynamics (QCD) with exceptional precision. It covers perturbative predictions (fixed-order, resummation, and NNLO where available), non-perturbative effects via power corrections, and detailed Monte Carlo modeling to connect partons to hadrons. Key outcomes include precise determinations of the strong coupling α_S(m_Z), evidence for asymptotic freedom across wide energy ranges, and robust confirmations of QCD gauge structure through color-factor measurements. The work highlights the power of clean e+e- environments for validating QCD and sets a benchmark for future high-energy colliders and precision QCD calculations.

Abstract

The current status of tests of the theory of strong interactions, Quantum Chromo Dynamics (QCD), with data from hadron production in e^+e^- annihilation experiments is reviewed. The LEP experiments ALEPH, DELPHI, L3 and OPAL have published many analyses with data recorded on the Z^0 resonance at sqrt(s)=91.2 GeV and above up to sqrt(s)>200 GeV. There are also results from SLD at sqrt(s)=91.2 GeV and from reanalysis of data recorded by the JADE experiment at 14<sqrt(s)<44 GeV. The results of studies of jet and event shape observables, of particle production and of quark gluon jet differences are compared with predictions by perturbative QCD calculations. Determinations of the strong coupling constant alpha_S(M_Z) from jet and event shape observables, scaling violation and fragmentation functions, inclusive observables from Z^0 decays, hadronic tau decays and hadron production in low energy e^+e^- annihilation are discussed. Updates of the measurements are performed where new data or improved calculations have become available. Finally, investigations of the gauge structure of QCD are summarised.

Figures (29)

• Figure 1: Schematic view of a $\mathrm{e^+e^-}\rightarrow\mathrm{hadrons}$ event; $\sqrt{s'}$ denotes the invariant mass of the hadronic system, usually close the nominal cms energy $\sqrt{s}$ of the experiment.
• Figure 2: Feynman diagrams of the three fundamental QCD processes.
• Figure 3: Sketch of a $\mathrm{q\mathrm{\overline{q}}}$ system in $\eta'-k_{\mathrm{t}}$ space.
• Figure 4: Jet production rates with the Durham (left) and JADE (right) algorithms measured at various values of $y_{\mathrm{cut}}$ by L3 l3290. The 2-, 3-, 4- and 5-jet production rates corrected for experimental effects are shown as points with error bars; the lines indicate the corresponding Monte Carlo model predictions as indicated on the figures.
• Figure 5: 3- and 4-jet production rates with the Durham algorithm measured by JADE at $\sqrt{s}=35$ GeV (triangles) and OPAL at $\sqrt{s}=91$ GeV (points) and 189 GeV (squares) OPALPR299. The data are corrected for experimental effects. The predictions by Monte Carlo models are indicated by the lines for PYTHIA (solid), HERWIG (dashed), ARIADNE (dotted) and COJETS (dash-dotted).