Compelling evidence for a new force of nature discovered by international physicists

Researchers say the data challenges the way we think about how the universe works

There is strong evidence for a new force of nature, said physicists working on an international science experiment.

Researchers from the UK's Science and Technology Facilities Council cited "a much-anticipated result" from the Fermi National Accelerator Laboratory in Illinois, in the US.

The Muon g-2 experiment provided evidence that elementary particles, called muons, are not behaving in the way they are supposed to, according to the leading theory of physics, known as the Standard Model.

It is an exciting time to be a particle physicist. We know that our current understanding of the universe is incomplete

Prof Mark Thomson, executive chair of the Science and Technology Facilities Council

This led researchers to believe a new force, or an undiscovered subatomic particle, must be causing the unexpected phenomenon.

At present, there are four fundamental types of forces that interact with matter to define our universe.

They are the electromagnetic and gravitational forces that we interact with every day, and the strong and weak interactions, which occur at a much smaller scale.

The science behind the existence of a fifth force is tricky for a layman to understand, but the physicists working on the discovery lauded it as baffling, thrilling and a "decade in the waiting".

"Today is an extraordinary day, long awaited not only by us but by the whole international physics community," said Graziano Venanzoni, co-spokesman of the Muon g-2 experiment and a physicist at Italy's National Institute for Nuclear Physics.

"A large amount of credit goes to our young researchers who, with their talent, ideas and enthusiasm, allowed us to achieve this incredible result."

Prof Mark Thomson, executive chairman of the Science and Technology Facilities Council, described this year as "an exciting time to be a particle physicist".

"We know that our current understanding of the universe is incomplete. What we are now seeing from leading experiments, such as g-2, could be the first glimpses behind the curtain into a new world of physics," he said.

"I look forward to the coming years and seeing the next piece of the puzzle fall in place."

What is the Muon g-2 experiment?

The test searches for signs of new particles and forces by precisely examining the muon’s interaction with a surrounding magnetic field.

The muon, when placed in the magnetic field, acts like a tiny magnetic compass and gyroscope. This compass rotates at a precise frequency, predicted by the Standard Model of physics.

The g-2 collaboration, however, measured this rotation to be faster than predicted.

This suggests that our current understanding of physics is incomplete.

It also hints at the presence of additional particles or hidden subatomic forces.

Could the evidence be inaccurate?

This result has been anticipated for more than a decade since a measurement published in 2006 from an experiment at Brookhaven National Lab in the US stood at odds with the Standard Model.

Physicists said that the outcome can not be 100 per cent certain, because it pushes the precision of the Fermilab experiment into uncharted territory.

The result "falls short of the one in a million gold standard used in particle physics to claim a discovery, but we are already analysing much more data that will significantly improve the precision of the measurement by more than a factor of two", said Prof Mark Lancaster, the UK lead for the g-2 experiment.

"This result, along with other recent developments including the LHCb result (Large Hadron Collider beauty) last week, could suggest that scientists are on the precipice of a new era of physics.

"We know our current list of fundamental particles and forces is incomplete because they are not sufficient to explain the dark-matter content of the universe or that the universe has very little anti-matter," he said.

Updated: April 8, 2021 04:28 PM

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