The 2020 Theory Initiative White Paper value for the weak force contribution to muon g-2 was 153.6(1.0) × 10^−11.
This improved calculation produces a best fit value that is 0.8 x 10^−11 larger (which brings the total value of muon g-2 slightly closer to the experimental value), and has a 60% smaller uncertainty (which is always an improvement even if it is a slight one).
The new calculation is consistent with the old one at the one sigma level.
A precise evaluation of the electroweak contribution to the anomalous magnetic moment of the muon requires control over all aspects of the Standard Model, ranging from Higgs physics, over multi-loop computations for bosonic and (heavy-)fermion diagrams, to non-perturbative effects in the presence of light quarks. Currently, the dominant uncertainties arise from such hadronic effects in the vector-vector-axial-vector three-point function, an improved understanding of which has recently emerged in the context of hadronic light-by-light scattering. Profiting from these developments as well as new perturbative and non-perturbative input for the charm contribution, we obtain a(EW)(μ) = 154.4(4) × 10^−11.
From Martin Hoferichter, Jan Lüdtke, Luca Naterop, Massimiliano Procura, Peter Stoffer, "An improved evaluation of the electroweak contribution to (g−2)μ" arXiv:2503.04883 (March 6, 2025).
The previous state of the art gap between experiment and the SM calculation was 6.5 ± 41.3. This development reduces the gap to about 5.7 ± 41.2 (which is about 0.14 sigma).
In other words, the experimentally measured value of muon g-2 (which has parts per 10 million precision) is perfectly consistent with the leading Standard Model predictions for the value of muon g-2 and there is basically no room for beyond the Standard Model physics that can perceptibly impact muon g-2.
It also reduces the EW share of the QED + EW component of the uncertainty in the total result from about 90% to 80%.
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