Experimental Tests of Asymptotic Freedom

TL;DR

This paper reviews experimental evidence confirming asymptotic freedom in Quantum Chromodynamics, showing that the strong coupling decreases at high energies as predicted, with updated measurements supporting the theory.

Contribution

It provides a comprehensive summary of experimental tests of asymptotic freedom, updating the world average of the strong coupling constant with improved precision.

Findings

Verification of the running of $\\as$ consistent with QCD

Updated world average of $\amz = 0.1189 \pm 0.0010$

Strong experimental support for asymptotic freedom

Abstract

Quantum Chromodynamics (QCD), the gauge field theory of the Strong Interaction, has specific features, asymptotic freedom and confinement, which determine the behaviour of quarks and gluons in particle reactions at high and at low energy scales. QCD predicts that the strong coupling strength $\as$ decreases with increasing energy or momentum transfer, and vanishes at asymptotically high energies. In this review, the history and the status of experimental tests of asymptotic freedom are summarised. The world summary of measurements of $\as$ is updated, leading to an unambiguous verification of the running of $\as$ and of asymptotic freedom, in excellent agreement with the predictions of QCD. Averaging a set of measurements balanced between different particle processes and the available energy range, results in a new and improved world average of $\amz = 0.1189 \pm 0.0010 .$