New force of nature discovered by scientists at Fermilab

Scientists have detected potential evidence of a new natural force as they observe the unconventional behavior of muons, minuscule particles, within a magnetic field.
Rizwan Choudhury
Muon g-2 experiment at Fermilab.
Muon g-2 experiment at Fermilab.

Credits: Reidar Hahn, Fermilab 

Scientists working at a particle accelerator near Chicago may be on the brink of discovering a new force of nature that could revolutionize our understanding of the universe.

They have found more evidence that muons, tiny sub-atomic particles, are not behaving as expected by the current physics theory. An international team of scientists working on the Muon g-2 experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory announced the much-anticipated updated measurement on Thursday in a press release

This new result strengthens their first result from April 2021 and creates a significant conflict between what the theory says and what the experiment shows after 20 years of work. The results have been submitted in the Journal Physical Review Letters.

What are Muons?

Muons are fundamental particles similar to electrons but about 200 times as massive. Like electrons, muons have a tiny internal magnet that wobbles like the axis of a spinning top in the presence of a magnetic field. The precession speed in a given magnetic field depends on the muon magnetic moment, typically represented by the letter g; at the most superficial level, theory predicts that g should equal 2.

However, in an experiment called g-2 (pronounced gee minus two), the researchers used powerful, superconducting magnets to make the muons wobble as they traveled around a 15-meter ring at nearly the speed of light.

The results showed that the muons wobbled faster than the standard model, the best theory to describe the sub-atomic world, said it should. 

A leading researcher on the project, Prof Graziano Venanzoni from Liverpool University, told BBC that an unknown new force might cause this phenomenon. He called it the ‘fifth force’ and said it was a mysterious and significant discovery that revealed something new about the universe.

The findings are not yet conclusive, as they have a statistical significance of 4.2 sigma, which means there is a one in 40,000 chance that they are due to a random fluctuation.

The scientific standard for discovery is 5 sigma, which means a one in 3.5 million chance of being wrong.

The Muon g-2 collaboration’s co-spokesperson, Peter Winter, expressed his admiration for the remarkable experimental achievement of measuring the muon’s magnetic moment with such a low level of systematic uncertainty, which was not expected to be attained so soon.

The team hopes to reach that level of certainty by collecting more data and reducing the uncertainty in their measurements.

Rival experiment at the Large Hadron Collider

They also face competition from a rival experiment at the Large Hadron Collider (LHC) in Europe, looking for signs of new physics beyond the standard model.

Dr. Mitesh Patel from Imperial College London, who is part of the LHC experiment, said that finding evidence contradicting the standard model would be a significant breakthrough in physics.

“The standard model has been tested for over 50 years and has survived all experimental challenges. It would be revolutionary to find something that it cannot explain.”

The standard model cannot account for many phenomena observed in the universe, such as the acceleration of galaxies due to dark energy or the rotation of galaxies due to dark matter. These mysterious forces and particles are not part of the standard model.

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