The measurement of muon $g-2$ at Fermilab
The Muon g - 2 Experiment at Fermilab (E989) was built to repeat and improve the previous E821 Experiment at Brookhaven National Laboratory (BNL), aiming to reduce the experimental error by a factor of 4 to the final accuracy of 140 parts per billion (ppb). On April 7th, 2021, the E989 collaboration published the first result based on the first year of data taking (Run-1), measuring a μ = 0.001 165 920 40(54) with a precision of 460 ppb. The measured value is consistent with the BNL measurement and strengthens the long-standing tension with the data-driven SM prediction to a combined discrepancy of 4.2σ. On the theory side, however, new efforts involving lattice-QCD techniques are starting to question the current consensus on the theoretical prediction, demanding new improvements on both the experimental and theoretical sides. The Muon g - 2 Experiment at Fermilab has now concluded its sixth and final year of data taking, and a new result based on the Run-2 and Run-3 data was published in August 2023. This paper briefly describes the Muon g - 2 Experiment at Fermilab and its current status.