Precision physics with inclusive QCD processes

TL;DR

This paper reviews how inclusive QCD processes involving electroweak currents enable precise tests of Quantum Chromodynamics, including accurate measurements of the strong coupling constant and verification of asymptotic freedom.

Contribution

It provides a comprehensive analysis of the theoretical and experimental status of inclusive hadron production processes and their role in testing QCD at high precision.

Findings

Theoretical predictions for key processes reach accuracy of order α_s^4.

Precise measurements of Z and τ widths determine the strong coupling at different scales.

Experimental results confirm asymptotic freedom in QCD.

Abstract

The inclusive production of hadrons through electroweak currents can be rigorously analysed with short-distance theoretical tools. The associated observables are insensitive to the involved infrared behaviour of the strong interaction, allowing for very precise tests of Quantum Chromodynamics. The theoretical predictions for $\sigma(e^+e^-\to\mathrm{hadrons})$ and the hadronic decay widths of the $\tau$ lepton and the $Z$, $W$ and Higgs bosons have reached an impressive accuracy of $\mathcal{O}(\alpha_s^4)$. Precise experimental measurements of the $Z$ and $\tau$ hadronic widths have made possible the accurate determination of the strong coupling at two very different energy scales, providing a highly significant experimental verification of asymptotic freedom. A detailed discussion of the theoretical description of these processes and their current phenomenological status is presented. The most precise determinations of $\alpha_s$ from other sources are also briefly reviewed and compared with the fully-inclusive results.