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Muon g–2: challenge to particle physics

  • Posted By
    10Pointer
  • Categories
    Science & Technology
  • Published
    9th Apr, 2021

Context

The newly published results of an international experiment show the possibility of new physics which would govern the laws of nature.

Key-highlights of the Study

  • A subatomic particle called the muon were studied.
    • The results show that the particles do not match the predictions of the Standard Model.
  • Experiment:The experiment which is called Muon g–2 (g minus two) was conducted at the US Department of Energy’s Fermi National Accelerator Laboratory (Fermilab).
    • The quantity which was measured is called the g–factor which is a measure that derives from the magnetic properties of the muon.
    • Muons act as a tiny internal magnet.
    • In a strong magnetic field, the direction of this magnet “wobbles” like the axis of a spinning top.
    • The rate at which the muon wobbles is described by the g-factor, the quantity that was measured.
    • This value is known to be close to 2, so scientists measure the deviation from 2. Hence the name g–2.
    • The g-factor can be calculated precisely using the Standard Model.

How does it work?

  • In the g–2 experiment, scientists measure it with high-precision instruments.
  • They generate muons and got them to circulate in a large magnet.
  • The muons interact with a “quantum foam” of subatomic particles “popping in and out of existence”.
  • These interactions affect the value of the g-factor, causing the muons to wobble slightly faster or slightly slower.
  • If the quantum foam contains additional forces or particles that are not accounted for by the Standard Model, that would tweak the g-factor further and a different result is observed from the standard results.
    • By calculating the deviation which is called anomalous magnetic moment the results are observed.

Muon

  • The muon is one of the leptons.
  • It is similar to electron and 200 times larger.
  • It is much more unstable than electron and survives for a fraction of a second.
  • Muons act as a tiny internal magnet.
  • In a strong magnetic field, the direction of this magnet “wobbles” like the axis of a spinning top.

What were the findings?

  • The results, while diverging from the Standard Model prediction.
  • The results hint at the existence of unknown interactions between the muon and the magnetic field.
  • This interactioncould involve new particles or forces.

About Standard Model

  • The Standard Model is a theory to predict the behaviour of the building blocks of the universe.
  • It forms the rules for six types of quarks, six leptons, the Higgs boson, three fundamental forces, and how the subatomic particles behave under the influence of electromagnetic forces.
  • The g-factor can be calculated precisely using the Standard Model.