Question

What is magnetic moment of Muon, why it is abnormal?

Answer 1

The muon is a spin-$\frac{1}{2}$ charged particle characterized by an intrinsic magnetic

moment with a gyromagnetic ratio, g, that is very close to 2. Its variance from 2,

referred to as the magnetic moment anomaly

$$a_\mu=\frac{g-2}{2}$$

, has been determined over the last decades to ever higher precisions in both experiment and theory.However, the experimental value is higher than the predicted value by more than 3 standard deviations which suggests the possibility of new physics. A confirmation of the difference between experiment and theory will have an impact on new physics models in the TeV scale.