How the anomalous magnetic moment of the muon opens a window beyond the standard model

The anomalous magnetic moment of the muon has recently been measured with an accuracy of 7.10-7 that is 14 times better than the previous measurement performed at CERN. This value is aμ = 1,1659203(8).10-3. At this level aμ is sensitive to quantum electrodynamics, this accuracy implies the most constraining information about the existence of a sub-structure inside the muon: if this structure exists, it will appears on distances below 5.10-20 m. (A.C.)