Muon g–2: New physics governing the laws of nature

Muon g–2: New physics governing the laws of nature

Part of: GS Prelims and GS – III – Sci & tech 

In news

• Newly published results of an international experiment hint at the possibility of new physics governing the laws of nature.
• The experiment, called Muon g–2 (g minus two), was conducted at the US Department of Energy’s Fermi National Accelerator Laboratory (Fermilab).

Key takeaways 

• The experiment studied a subatomic particle called the muon. 
• Its results do not match the predictions of the Standard Model, on which all particle physics is based. 
• The results instead reconfirm a discrepancy that had been detected in an experiment 20 years ago.
• Concluded in 2001, the Brookhaven experiment came up with results that did not identically match predictions by the Standard Model.
• The Muon g–2 experiment measured this quantity with greater accuracy.

What is the Standard Model?

• The Standard Model is a rigorous theory that predicts the behaviour of the building blocks of the universe.
• It lays out 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 muon is one of the leptons.
• It is similar to the electron, but 200 times larger, and much more unstable, surviving for a fraction of a second.

What quantity was measured?

• g–factor was measured. 
• It is a measure that derives from the magnetic properties of the muon.
• The rate at which the muon wobbles is described by the g-factor.
• This value is known to be close to 2, so scientists measure the deviation from 2. Hence the name g–2.
• The new experimental results (combined from the Brookhaven and Fermilab results) announced are:
• g-factor: 00233184122

• anomalous magnetic moment: 00116592061.