The muon g-2 experiment: overview and prospects

The muon gyromagnetic factor $g_\mu$ has long occupied a prominent place among the observables used in precision tests of the Standard Model (SM). The current discrepancy between the SM prediction and the value measured by the Brookhaven E821 Experiment stands at about 3.5 standard deviations, with comparable experimental and theoretical uncertainties. Two new experiments, one at Fermilab and the other at J-PARC, aim to improve the experimental uncertainty by a factor of 4. Meanwhile, the SM prediction is also expected to undergo a significant increase in precision. We review the status of the Fermilab experiment E989, currently operational and undergoing commissioning. E989 will analyze 21 times more muon decays than BNL E821, and is also poised to reduce the systematic uncertainty by a factor of 3. The overall goal of E989 is to achieve the precision of 0.14 ppm for $a_\mu = (g_\mu -2)/2$.