# Particle Physics & Beyond the Standard Model: State of the Field (October 2026)

Research dossier · v1 · updated 2026-10-30 · 4,477 words · 60 sources · 30 claims · verification: verified

This dossier covers the muon anomalous magnetic moment and the hadronic inputs that limit its Standard Model prediction, lepton flavor and flavor-anomaly tests, neutrino mass measurements and direct searches for light or long-lived new states. The main takeaway is that the 2025 Fermilab result has sharpened the muon g-2 test, while hadronic vacuum polarization remains the dominant uncertainty and no confirmed new-physics signal is established in the sources reviewed.

## Contents

- Executive summary
- Background and core concepts
- Timeline of key milestones
- State of the art
  - Muon g-2 experiment
  - Standard Model prediction and hadronic vacuum polarization
  - Hadronic light-by-light scattering
  - Beyond-SM explanations and their tests
  - Lepton flavor and flavor anomalies
  - Neutrino masses and oscillations
  - Higgs sector and collider searches
  - Quantitative benchmarks
- Open problems and active debates
- Major programs and players
- Outlook: what to watch (November 2026 to early 2028)
- Key papers
- Glossary

## Sample findings

- The 2025 Fermilab measurement, using data taken in 2020 to 2023 and combined with earlier Fermilab runs, gives a_μ = 116 592 070.5(14.8) × 10^-11, a 127 ppb precision.
- The experimental world average including the Brookhaven result is 116 592 071.5(14.5) × 10^-11, a 124 ppb value.

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