g-2 short study and discussion
The Muon g-2 experiment measures the magnetic moment of the muon with high precision. The results are, well, interesting.
Images courtesy of Fermi National Accelerator Laboratory,
Workshop Group Tutorial for Teachers
Questions:
- What are magnetic moment (hyperphysics) and gyromagmnetic ratio (Almost Complex Structure)?
- How do these show up for a small charged particle moving in a magnetic field? Time for a crazy human trick!
- What do we mean by g-2? (Hint: It is not 7.81 m/s2.)
- The theoretical value of g, according to the Standard Model, is g = 2.00233183620(86).
- According to QED, g = 2. The remaining decimals are from QCD and the Standard Model.
- To get the anomalous magnetic moment, aμ first get the difference between the full theoretical value of g and the QED value of g, which we'll call gQED. Then divide by gQED. In (no) other words, aμ = (g - gQED)/gQED = (g-2)/2.
- Can you find the theoretical value of the anomalous magnetic moment, aμ?
- Now let's make sense of the chart below from Fermilab.
In case you missed the calculation, theoretical aμ = 0.00116591810(43).
Resources:
- Fermilab Muon g-2 ← primary (use side menu)
- First results at Fermilab
- Wikipedia
- Video: What does the Muon g-2 experiment tell us?
Probing Deeper:
- Muon g-2: A review, Nuclear Physics B, Volume 975, February 2022