$$a_\mu(\text{FNAL}) = 116{,}592{,}040(54)\times10^{-11}$$

Equation 9 · Physics

From Origins to Frontier: A History of Particle Physics Beyond the Standard Model

This equation states an equality: the expressions on both sides have the same value under the article’s assumptions.

Contrast that with the muon’s anomalous magnetic moment, $a_\mu$ = (g-2)/2 , which remains unresolved. The Fermilab Muon g-2 experiment’s most precise measurement to date, released in August 2023, gives $a_\mu(\text{FNAL})$ = 116{,}592{,}040(54)$\times$10^{-11} , a result precise to 0.20 parts per million [ 5 , 6 ] . Combined with the experiment’s earlier data, the measured value differs from one widely used Standard Model theoretical prediction by (251$\pm$59)$\times$10^{-11} , a discrepancy the collaboration itself describes as reaching 4.2 standard deviations [ 6 ] . This is a genuine, still-live tension, and it is also a genuine, still-live disagreement among theorists — not about the experimental…

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