HEP In the literature: partially resolved

Does the SM match the final muon g-2 measurement?

In plain words

The muon behaves like a tiny magnet whose strength was measured to about one part in ten million. The SM prediction now agrees, but only after replacing one method of computing the strong-force part with another.

Precise statement

Fermilab's final result (2025) gives $a_{\mu} = 116592070.5(14.8) x 1e-11\ (127\ \mathrm{ppb})$; the world average with BNL is $116592071.5(14.5) x 1e-11\ (124\ \mathrm{ppb})$; the 2025 Theory Initiative prediction using lattice-QCD HVP (hadronic vacuum polarization) is $116592033(62) x 1e-11$, in agreement. The residual question is whether the SM prediction with uncertainty $\sim 20 x 1e-11$ still agrees once data-driven and lattice HVP are reconciled.

What would settle it

Lattice HVP at $\sim 0.2\ \mathrm{percent}$ from several groups, consistent $e+e-$ hadronic data, the MUonE spacelike HVP measurement, and the J-PARC muon $g-2$ experiment.

Status in the literature

Unverified note

In 2025 the long-standing $4\ \text{to}\ 5\,\sigma$ discrepancy disappeared with the lattice-based SM value; the data-driven value remains inconsistent.