Muon g-2

Context:

A new research has identified existence of new physics governing the laws of nature. They do not match observations of standard model.

Background

Scientists studied a subatomic particle called muon that has confirmed a discrepancy that had been observed in an experiment 20 years previously.

Details

• The standard model is a fundamental Physics theory that predicts the behaviour of the building blocks of the universe.

• It provides rules for six types of quarks, the Higgs boson, six leptons, three fundamental forces, and how the subatomic particles act under the influence of electromagnetic forces.

• Muon is one of the leptons that is similar to electrons but about 200 times more than its size. It is more stable and survives for a fraction of a second.

Experiment

• The experiment of muon g-2 was done at the US Department of Energy’s Fermi National Accelerator Laboratory (Fermilab).

• The experiment measured quantity of muon. It was continuation of Brookhaven experiment that did not match predictions by the Standard Model.

• The muon g-2 experiment tried to measure quantity more precisely. It tried to find if discrepancy was consistent or the result would be similar to standard model.

Measuring quantity

• Quantity is measured through g-factor. As muon is unstable, scientists study the effects it has on the gravity of its surroundings.

• The g-factor can be calculated using standard model. Scientists measured it precisely during g-2 experiment.

Indication of results

• The results show the existence of interactions between the muon and the magnetic field that is possibly due to new particles or forces.

• There is no enough deviation to claim a discovery. The difference with the results of Fermi lab is 4.2 standard deviations whereas 5 standard deviations are required.