Abstract
As mentioned above, the Standard Model of particle physics has been extraordinarily successful. One of these successes has been the calculation of the anomalous magnetic moments, or the g factor, of both the electron and the muon. In 2001, however, a tantalizing two-standard deviation between the calculation of the g factor and its measured value was found. Recent work on both theory and experiment has made that difference larger, although it still does not have sufficient statistical significance to make a discovery claim. Further complexity has been added by a second theoretical calculation, using a different method, that agrees with the measured result. Pursuit on both theory and experiment continues.
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Notes
- 1.
A g-factor (also called g value or dimensionless magnetic moment) is a dimensionless quantity that characterizes the magnetic moment and angular momentum of an atom, a particle or the nucleus. It is essentially a proportionality constant that relates the different observed magnetic moments μ of a particle to their angular momentum quantum numbers and a unit of magnetic moment (to make it dimensionless), usually the Bohr magneton or nuclear magneton. See Aoyama et al. (2007).
- 2.
For details of parity nonconservation in the weak interactions see Chap. 3 of this book.
- 3.
The information about the blind analysis was presented by Gerry Bunce in a seminar at the University of Colorado and in private conversation. It does not appear in the published paper.
- 4.
(14) and (6) were the statistical and systematic uncertainties in aμ, respectively.
- 5.
The group had published updates in 2002 and 2004.
- 6.
At this time a 5-sigma effect was needed to make a discovery claim.
- 7.
This was based on the 2004 result published by the Brookhaven group not the final 2006 result.
- 8.
This move took place in 2013 and took 35Â days.
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Laymon, R., Franklin, A. (2022). The Anomalous Magnetic Moment of the Muon. In: Case Studies in Experimental Physics. Synthesis Lectures on Engineering, Science, and Technology. Springer, Cham. https://doi.org/10.1007/978-3-031-12608-6_7
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