g-2 precession in a storage ring — Feynman loop corrections to g-factor
The muon g-factor deviates from the Dirac value of 2 by aμ = (g−2)/2 ≈ 116×10⁻⁵. Fermilab measures this via the anomalous precession frequency ωa = aμ·eB/m. The current 4.2σ discrepancy between the Standard Model prediction (116591810 ×10⁻¹¹) and experiment (116592061 ×10⁻¹¹) may signal new physics beyond the SM.