arXiv:2205.01169hep-ph
Experimental determination of the QCD effective charge $α_{g_1}(Q)$
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Abstract
The QCD effective charge $α_{g_1}(Q)$ is an observable that characterizes the magnitude of the strong interaction. At high momentum $Q$, it coincides with the QCD running coupling $α_{\rm s}(Q)$. At low $Q$, it offers a nonperturbative definition of the running coupling. We have extracted $α_{g_1}(Q)$ from measurements carried out at Jefferson Lab that span the very low to moderately high $Q$ domain, $0.14 \leq Q \leq 2.18$ GeV. The precision of the new results is much improved over the previous extractions and the reach in $Q$ at the lower end is significantly expanded. The data show that $α_{g_1}(Q)$ becomes $Q$-independent at very low $Q$. They compare well with two recent predictions of the QCD effective charge based on Dyson-Schwinger equations and on the AdS/CFT duality.
Link to preprint: https://arxiv.org/abs/2205.01169
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Unfortunately this is usually plotted as momentum vs coupling, which, if you wave your hands around the uncertainty principle enough, is sort of the reciprocal of the same thing. You can find a plot in the preprint: https://arxiv.org/abs/2205.01169
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