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8 billion wobbling muons just put particle theory on notice

8 billion wobbling muons just put particle theory on notice

May 9, 2021 at 9:52am

Jason Bono was one of the researchers behind a major scientific moment — when tiny particles unexpectedly unraveled one of the most important and successful theories in physics.

Bono, who earned his Ph.D. in physics from FIU in 2014, was part of an international team of 160 physicists who worked on the Muon g-2 experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory. They found these tiny particles — called muons — may be interacting with undiscovered particles or forces.

So what does that mean? There may be a fifth fundamental force of nature. This could upend what we know about particle physics, launching a new era of breakthroughs that would advance our current understanding of the universe.

When the Muon g-2 team measured the muons — the more massive, heavier cousins to the simple electrons — they noticed their measurement didn’t align with the Standard Model, which is the core theory of particle physics. Something was off. And it was off with each of the more than 8 billion muons the team analyzed. 

Muons have remained a bit of a mystery since 2001 when a team at Brookhaven National Laboratory found a discrepancy with their muon measurements. The Muon g-2 team built on this work, conducting their own independent measurements at Fermilab. Their results agreed with Brookhaven’s.

The more recent results, though, are especially exciting because they provide more evidence something’s definitely going on with the muon.

“We knew that if we found a difference in the measurement from the Standard Model, we wouldn’t know exactly what’s causing it, but we would know it’s something that we don’t understand yet — and that’s a victory in itself,” Bono said.

For the physics community, this new evidence is a gamechanger. Unlike the 2012 discovery of the Higgs boson, a particle that gives other particles mass, which scientists always expected to find one day, the results from the Muon g-2 experiment were unexpected. They open up new possibilities, suggesting there’s something else that exists beyond the theory. 

One of the most surprising things physicists found was how much muons wobble. Like electrons, muons are magnetic. When measuring the magnetic strength of any particle, scientists put it near a magnet in a magnetic field, and then measure the direction of a muon’s wobble. A faster wobble means a stronger magnetism. And it turns out muons wobble a lot.

Bono never dreamed he’d be part of such an achievement. As a kid, he spent hours reading about physics. He grew up and studied physics, but found that the field of particle physics moves slowly. Discoveries are rare events. For this reason, Bono decided that he would leave the field of particle physics. But before departing, would join the g-2 collaboration.

“These results are like a glimmer of hope there’s more discoveries on the way,” Bono said. “To be part of this is hard to describe. It’s so amazing.”

The g-2 collaboration will release higher quality data in the coming years. At the same time, the theory community is ironing out details in the Standard Model calculation. With both efforts well underway, it's possible that within two years the threshold for a discovery will be crossed.

For now, Bono is trying something new. He’s in Washington, D.C. for an American Association for the Advancement of Science (AAAS) science and technology policy fellowship that places scientists into government positions to help solve societal challenges. He’s working on national security analysis at the Pentagon. It may seem like a drastic shift from working with muons, but in a way, it’s also very similar — he's using data and math to address large, unanswered questions.