Does the muon g−2 anomaly indicate new physics?

The anomalous magnetic moment of the muon, measured at Fermilab, deviates from the Standard Model prediction at roughly 4–5σ. The magnitude of the discrepancy depends on which hadronic vacuum polarisation computation is used.

Lattice QCD results from the BMW collaboration weaken the tension with the SM, while data-driven estimates strengthen it. Resolution requires both better theory and further measurements.