LIP Lisboa

First resultsfrom the Muon 𝑔−2 Experiment at Fermilab

by Dr Alessandra Lucà (Fermilab)


Over the last decades high-precision measurements of the muon magnetic anomaly, 𝑎𝜇=(𝑔𝜇−2)/2, have been carried out motivated by the fact that a direct comparison with theStandard Model (SM) prediction serves as an excellent test of its completeness.The E821experiment at the Brookhaven National Laboratory (BNL)measured 𝑎𝜇 with a precision of 0.54 parts per million (ppm) and resulted in a 3.7 standard deviations discrepancy with the SM expectation. This intriguing finding motivated the construction of the E989 Muon 𝑔−2 experiment at Fermilab, which was designed to test the validity of the BNL result, and to further improve the experimental precision.This talk presents the first results of the experiment at Fermilab, which recently measured the positive muon magnetic anomaly with a precision of 0.46 ppm, using data collected during its first physics run in 2018. The result is in excellent agreement with the BNL measurement, and the combined experimental average increases the significance of the discrepancy between the measured and SM predicted 𝑎𝜇 to 4.2 standard deviations, strengthening possible hints of new physics.