On the challenge of measuring the colour charge of gluons

Abstract

We propose two ways of measuring “directly” the chromodynamic gluon self-couplings. We argue that the measurements would serve to establish (or disprove) the gauge and non-Abelian nature of the candidate strong-interaction theory: QCD. Both experiments concern the production in e+e− annihilation of a heavy vector meson resonance, followed by its hadronic decay into three “gluon jets”. The asymmetry of the decay plane relative to the electron axis is a measure of αS = g24π, with g the coupling for gluon self-interactions. If QCD is right, this value of g should coincide with the measured coupling of quarks to gluons. The two proposed experiments are difficult: they both demand very large statistics, one requires longitudinally polarized beams, the other the detection of weak-electromagnetic interferences. But the stakes are high.