The calibration system of the new g-2 experiment at Fermilab

The muon anomaly ( g − 2 ) μ / 2 has been measured to 0.54 parts per million by E821 experiment at Brookhaven National Laboratory, and at present there is a 3–4 standard-deviation difference between the Standard Model prediction and the experimental value. A new muon g−2 experiment, E989, is being prepared at Fermilab that will improve the experimental error by a factor of four to clarify this difference. A central component to reach this fourfold improvement in accuracy is the high-precision laser calibration system which should monitor the gain fluctuations of the calorimeter photodetectors at 0.04% accuracy.