Papers · William Alexander Aldred

The Anomaly Retired; the Defect Moved House: Muon g−2 After the Final Number

Publicly deposited November 1, 2026 · Zenodo · 4 pp · DOI: 10.5281/zenodo.23865298

Abstract

The Fermilab Muon g−2 experiment's final result (June 2025) fixes the experimental world average at a_μ^exp = 116592071.5 ± 14.5 (×10⁻¹¹). Against the 2020 Theory Initiative white paper (data-driven hadronic vacuum polarization), the defect was Δ = +261.5 ± 45.4 (×10⁻¹¹) — 5.8σ. Against the 2025 white paper, which replaced the data-driven HVP with the lattice-QCD evaluation, the defect is Δ = +38 ± 63 (×10⁻¹¹) — 0.6σ, nothing. The experiment did not move: both white papers face the same measurement. What moved is one theory input, the leading hadronic vacuum polarization, whose two independent reductions (dispersive (from e⁺e⁻ annihilation data) at 6931 ± 40 and lattice at 7132 ± 61 (×10⁻¹¹)) disagree with each other by 201 ± 73, a 2.76σ theory-versus-theory defect that is now the largest open wound in the quantity. The anomaly's death certificate therefore reads: killed not by a better measurement, and not by new physics, but by a change of theory method that is not itself yet settled — the e⁺e⁻ cross-section datasets behind the dispersive value contradict each other (the stated reason the 2025 paper abandoned them), and the second hadronic contribution, light-by-light, carries a pheno-versus-lattice split of 1.5σ with an error-inflation factor applied in print. Verdict: no case against the Standard Model — the anomaly is retired, and the defect has moved from experiment-versus-theory to theory-versus-theory, at 2.76σ, priced in §4. A discrepancy whose verdict flips with the choice of one input's reduction method was never a measurement of new physics. It was, all along, a measurement of the HVP problem, and the HVP problem is still open. ---

The result, in plain language

The muon g−2 anomaly was the loudest discrepancy in particle physics: experiment against theory at 5.8σ. Fermilab's final result fixes the measurement. What changed is not the experiment — it is one theory input, the hadronic vacuum polarization, whose evaluation method was replaced between the 2020 and 2025 white papers. Against the lattice evaluation, the defect is 0.6σ. Nothing.

What did not vanish is a defect — it moved house. The two reductions of that one input, dispersive and lattice, disagree with each other by 201 ± 73 (×10⁻¹¹), at 2.76σ, and that theory-versus-theory split is now the largest open wound in the quantity. The verdict is printed plainly: no case against the Standard Model; the anomaly is retired. A discrepancy whose verdict flips with the choice of one input's reduction method was, all along, a measurement of the HVP problem — and the HVP problem is still open.

Program note

Cube Campaign Batch 2, target C-12. The muon g−2 defect priced against both theory reductions on the final Fermilab number; every input checked against the published record during the run. Verdict, as the paper states it: no kill of the Standard Model — against the lattice reduction the anomaly is gone (0.60σ), and the defect now sits between the two theory reductions themselves, which disagree by 201 ± 73 (×10⁻¹¹), 2.76σ, on the final experimental number. The vacuum catastrophe remains unsolved, and this paper claims no result on it.

The program