The history of the muon (g-2) experiments

Journal Article · Wed Feb 20 00:00:00 EST 2019 · SciPost Physics Proceedings

DOI:https://doi.org/10.21468/SciPostPhysProc.1.032· OSTI ID:1495254

Roberts, B. Lee ^[1]

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1. Boston University

I discuss the history of the muon (g-2) $(g-2)$ measurements, beginning with the Columbia-Nevis measurement that observed parity violation in muon decay, and also measured the muon g $g$ -factor for the first time, finding g_\mu=2 $g_{\mu }=2$ . The theoretical (Standard Model) value contains contributions from quantum electrodynamics, the strong interaction through hadronic vacuum polarization and hadronic light-by-light loops, as well as the electroweak contributions from the W $W$ , Z $Z$ and Higgs bosons. The subsequent experiments, first at Nevis and then with increasing precision at CERN, measured the muon anomaly a_\mu = (g_\mu-2)/2 $a_{\mu }=(g_{\mu }-2)/2$ down to a precision of 7.3 parts per million (ppm). The Brookhaven National Laboratory experiment E821 increased the precision to 0.54 ppm, and observed for the first time the electroweak contributions. Interestingly, the value of a_\mu $a_{\mu }$ measured at Brookhaven appears to be larger than the Standard Model value by greater than three standard deviations. A new experiment, Fermilab E989, aims to improve on the precision by a factor of four, to clarify whether this result is a harbinger of new physics entering through loops, or from some experimental, statistical or systematic issue.

• Sponsoring Organization: USDOE
• OSTI ID: 1495254
• Journal Information: SciPost Physics Proceedings, Journal Name: SciPost Physics Proceedings Journal Issue: 1
• Publisher: Stichting SciPost
• Country of Publication: Country unknown/Code not available
• Language: English