New muon measurements could shatter standard physics theory

11 Aug 2023

The Muon g-2 magnet. Image: Ryan Postel/Fermilab

The latest results have moved scientists closer to disproving the standard model of particle physics, though uncertainty still remains.

A new study has bolstered the idea that an unknown fifth force of nature exists, as scientists work to analyse years of valuable data.

Currently, there are four known forces of nature that are constantly at work in the world – gravity, electromagnetism, the weak force and the strong force. But a landmark study in 2021 suggested there may be forms of matter and energy vital to the nature of the cosmos that are unknown to science.

Now, scientists at Fermilab – the US Department of Energy national accelerator laboratory – claim their latest result is the most precise measurement yet, raising hopes that they’re on track to shake up our understanding of physics.

The experiments focus on muons, fundamental particles that are similar to electrons but are more than 200 times heavier. The lab’s Muon g-2 experiments involve exposing muons to an intense magnetic field by sending them around a 50-foot-diameter magnetised ring.

When doing this, the team has found that muons wobble in unpredictable ways, which defies the fundamental theory of how particles interact.

Fermilab claims the latest results effectively doubles the precision of the results from 2021, decreasing the uncertainty that comes from “experimental imperfections”.

“This measurement is an incredible experimental achievement,” said Muon g-2 collaboration co-spokesperson Peter Winter. “Getting the systematic uncertainty down to this level is a big deal and is something we didn’t expect to achieve so soon.”

The Fermilab experiments build on a previous experiment at Brookhaven National Laboratory around 20 years ago. The US lab said the latest results have set up a “showdown” between theory and experiment, as it could disprove the standard model of particle physics.

However, Fermilab said the theory still faces “statistical uncertainty” due to the amount of data being analysed. The lab claims the latest result has added two years of data to their first result.

Researchers are currently working to incorporate six years of data into a final analysis,  which is expected to be completed in the next couple of years.

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Leigh Mc Gowran is a journalist with Silicon Republic