In news
Fermilab, which houses the American particle accelerator, has released the first results from its ‘muon g-2’ experiment
Details
- These results spotlight the anomalous behaviour of the elementary particle called the muon.
- The muon, a heavier cousin of the electron, is expected to have a value of 2 for its magnetic moment, labelled ‘g’.
- The muon exists not in isolation but embedded in a sea where particles are popping out and vanishing every instant due to quantum effects.
- So, its g value is altered by its interactions with these short-lived excitations.
Measured Value
- The muon g-2 experiment measured the extent of the anomaly
- Fermilab announced that the measured ‘g’ deviated from the amount predicted by the Standard Model.
- That is, while the calculated value in the Standard Model is 2.00233183620 approximately, the experimental results show a value of 2.00233184122.
- When the results are combined with those from a 20-year-old experiment at Brookhaven National Laboratory in the U.S., they show an accuracy of about 4.2 sigma.
- This means the possibility that this is due to a statistical fluctuation is about 1 in 40,000.
The g factor
- The muon is also known as the ‘fat electron’.
- It is produced copiously in the Fermilab experiments and occurs naturally in cosmic ray showers.
- Like the electron, the muon has a magnetic moment because of which, when it is placed in a magnetic field, it spins and precesses, or wobbles slightly, like the axis of a spinning top.
- Its internal magnetic moment, the g factor, determines the extent of this wobble.
- As the muon spins, it also interacts with the surrounding environment, which consists of short-lived particles popping in and out of a vacuum.
Source: The Hindu
