Physics at Virginia

The gyromagnetic ratio g for an elementary point-particle differs from the Dirac value of g = 2 by the “magnetic anomaly” a = (g − 2)/2 ≈ 10−3, due to couplings to virtual particles in the vacuum. Muon, through its greater mass, probes significantly deeper into the high-mass excitations of the vacuum than does the better studied electron. Hence, efforts to measure the muon magnetic anomaly aµ have persisted for decades, culminating in Fermilab E989, the Muon g−2 experiment. In July 2023, the E989 collaboration concluded data taking in Run-6, its last run cycle, and a few weeks later unblinded and published results of Run-2 and -3 data analysis, adding to the Run-1 results of 2021. The Run-2/3 results bring about a two-fold improvement in the precision of the world average of aµ. In parallel, recent theoretical and experimental developments regarding the hadronic vacuum polarization (HVP) have led to a reexamination of the context for the interpretation of the experimental value of aµ. This talk will examine the experimental method, uncertainties, and results of E989. We will place the new aµ result in the context of a changing HVP landscape, and discuss the future prospects for the field.

Friday, October 13, 2023
3:30 PM
Clark Hall, Room 107
Note special room.


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