The Particle Data Group value for the strong force coupling constant is 0.1180 ± 0.0009. This new determination, based upon earlier runs of LHC dijet data and lower energy HERA data, is consistent with the PDG value at the 0.1 sigma level.
The strong force coupling constant is pervasively important in almost all high energy physics calculations, but it known much less precisely (with just one part per 131 parts precision) than most other Standard Model or fundamental physical constants. So, pinning this down more precisely is always big deal.
The beta function that describes how the strong force coupling constant runs with energy scale is an exact theoretical prediction of the Standard Model, with no experimental uncertainties. The conference presentation's confirmation that the strong force coupling constant runs with energy scale just as predicted in the Standard Model, over four orders of magnitude of energy scale, is arguably an even more important confirmation of the Standard Model, because there are fewer experimental confirmations of this in the literature.
In this talk we present a determination of the strong coupling constant αs and its energy-scale dependence based on a next-to-next-to-leading order (NNLO) QCD analysis of dijet production.
Using the invariant mass of the dijet system to probe αs at different scales, we extract a value of αs(mZ) = 0.1178 ± 0.0022 from LHC dijet data.
The combination of various LHC datasets significantly extends the precision and scale reach of the analysis, enabling the first determination of αs up to 7 TeV. By incorporating dijet cross sections from HERA, we further probe αs at smaller scales, covering a kinematic range of more than three orders of magnitude. Our results are in excellent agreement with QCD predictions based on the renormalization group equation, providing a stringent test of the running of the strong coupling across a wide energy range.
João Pires, "Precision determination of αs from Dijet Cross Sections in the Multi-TeV Range" arXiv:2507.01670 (July 2, 2025) (Contribution to the 2025 QCD session of the 59th Rencontres de Moriond).
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