The muon g–2 anomaly refers to a persistent discrepancy between the predicted and experimentally measured value of the magnetic moment of the muon, a heavier cousin of the electron. This quantity, known as g, describes how a particle’s spin interacts with a magnetic field.
According to the Standard Model of particle physics, the muon’s g-factor should be slightly more than 2 due to quantum fluctuations involving known particles. However, precision experiments—most notably at Brookhaven National Laboratory and later at Fermilab—have shown that the actual value of muon g–2 is slightly larger than what theory predicts.
This small but significant difference suggests that unknown particles or forces may be influencing the muon’s behavior, offering a potential window into physics beyond the Standard Model. The anomaly could point to:
- Supersymmetric particles,
- Dark matter interactions,
- New gauge bosons,
- Or other exotic phenomena not yet observed.
Further theoretical work and more precise measurements are ongoing to determine whether this discrepancy is truly a sign of new physics or the result of missing effects in existing calculations. If confirmed, the muon g–2 anomaly could be one of the most important discoveries in fundamental physics in decades.