Physicists share the glory and the wealth after winning $3M for exploring muon mysteries

University of Washington physicist David Hertzog can’t wait to find out how hundreds of researchers who worked on a geeky project known as the Muon g-2 Collaboration will react when they hear they’ve each won thousands of dollars for that work.

The money is coming from this year’s $3 million Breakthrough Prize for fundamental physics, which was awarded tonight during a gala ceremony in Los Angeles. Hertzog and his colleagues decided that the prize should be divided equally among everyone who was an author on research papers relating to the decades-long series of muon experiments.

“There are students who were in and out of this thing — two years or less,” Hertzog said. “They’re going to be shocked out of their lives about something they did a long time ago that they don’t remember doing. They’re going to get a phone call or email from the Breakthrough people, and they’re going to go, ‘What!?’ That’s kind of fun.”

Hertzog said the money will be shared by about 400 researchers who were involved in the Muon g-2 experiments at Fermilab in Illinois and at the Brookhaven National Laboratory in New York. The prize also honors the role played by Europe’s CERN research center, going as far back as 1959. “There was one very, very old man who was still alive from the 1970s experiment, but I think he has died,” Hertzog said.

Although the precise math hasn’t yet been worked out, dividing $3 million among 400 people would give each recipient $7,500. “That’s nothing to throw around if you’re a student or a young postdoc,” Hertzog said.

A big moment for the muon

Russian-born tech investor Yuri Milner and his wife, Julia Milner, established the Breakthrough Prize in 2012 to recognize achievements in fundamental physics, mathematics and the life sciences. They also wanted to add some Hollywood-style pizazz to the public perception of scientists, going so far as to spread out a red carpet for celebrities at the “Oscars of Science.” The host for this year’s ceremony was James Corden, and the guest list included Robert Downey Jr., Eileen Gu, Anne Hathaway, Paris Hilton, Salma Hayek Pinault and Michelle Yeoh.

The $3 million Breakthrough Prize is the world’s richest scientific award, outdoing the roughly $1.2 million prize given to Nobel laureates. More than $344 million has been handed out since the creation of the prize program. Past winners from the University of Washington include physicists Eric Adelberger, Lukasz Fidkowski, Jens Gundlach and Blayne Heckel, plus biochemist David Baker.

This year’s prize in fundamental physics touches on a long-running effort to reconcile experimental findings with one of history’s most successful scientific theories: the Standard Model of particle physics. The theory lays out a framework for classifying and understanding a menagerie of subatomic particles — including the muon, which is similar to the electron but 207 times heavier.

The Standard Model predicts the various properties of the muon. One such property is the strength and orientation of the muon’s magnetic field, known as its magnetic moment. The theory’s simplest formulation calls for the value of the muon’s magnetic moment, represented in equations by the letter g, to be equal to 2.

Few things in particle physics are that simple, however. Experimental tests measured the g-factor to be slightly more than 2, and that discrepancy became the focus of the Muon g-2 (pronounced “mew-on gee-minus-two”) experiments.

If there was a confirmed mismatch between the Standard Model and experimental results, that could open the door to new physics. For example, perhaps whole new sets of subatomic particles not predicted by theory had somehow eluded direct observation. So, physicists across the globe marshaled their forces to determine the value of g, either to fill in the gap between experiment and theory or to zero in on a new frontier in physics.

Over the years, physicists have been conducting increasingly fine-tuned experimental runs using powerful magnets at CERN, Brookhaven and Fermilab. Hertzog has been in on the quest since Brookhaven joined in, about 30 years ago, and he was part of the team in 2013 when the experiment’s massive main magnet was moved from Brookhaven to Fermilab.

Each run narrowed the uncertainty surrounding the precise value of g. The crowning achievement came from Fermilab’s version of the experiment in 2025.

“We set the goal at 140 parts per billion, and we got 127 parts per billion,” Hertzog said. “When we wrote the proposal, we were ambitious as we could get in our minds, because we wanted to get people to take us on. Then we just blew away all the systematic errors, better than we expected. And then new ones came along, which caused us to have a little bit of a struggle.”

At the same time, other physicists were wrestling with theoretical models. They factored in the ever-so-subtle effects of particles popping in and out of the quantum foam that’s thought to make up the fabric of spacetime at its smallest scale. Last year, one of the models came up with a range of theoretical values for g that overlapped with the Muon g-2 Collaboration’s range of experimental values.

That led some to claim that there was no discrepancy after all. “A famous particle physics experiment has ended not with a bang, but a whimper,” Science magazine reported. But once again, few things in particle physics are that simple. Hertzog insisted that reports of the muon mystery’s death have been greatly exaggerated.

“I just throw up my hands, because after 30-some years of working on this, it’s a little disappointing that it’s not clear,” he said. “Not only has the number that they recommended shifted, but the certainty of their number got way wider. The uncertainty on the theory recommendation is actually pretty big. It’s shifted, but it’s also pretty large.”

Hertzog said the Breakthrough Prize recognizes a scientific quest that’s still in progress. “This story is not finished,” he said. “The story is really about the extraordinary achievement of the precision of this delicate measurement which probes nature to such a deep, deep level.”

Will there ever be a definitive answer to the muon mystery?

“We don’t know it yet, but it’s knowable, as opposed to walking out into a vast cloud of ambiguity,” Hertzog said. “So, I think we will find out in a couple of years where that finally lands. … Who knows whether that’ll lead us to another chapter in this business. But I’m confident that we’ll know it.”

A big night for breakthroughs

The Muon g-2 Collaboration’s Breakthrough Prize was awarded to hundreds of researchers from 31 institutions in seven countries, but just four team members were selected to take the stage for tonight’s award ceremony. Hertzog was joined by Chris Polly from Fermilab, William Morse from Brookhaven, and Lee Roberts from Brookhaven and Boston University.

A special lifetime prize for fundamental physics went to David Gross, a theorist at the Kavli Institute of Theoretical Physics at the University of California at Santa Barbara. Gross won a share of the 2004 Nobel Prize in Physics for filling gaps in the Standard Model relating to the strong nuclear force. More recently, he helped write a landmark 40-year national plan for particle physics.

Three prizes were given in the life sciences:

• Jean Bennett, Katherine High and Albert Maguire of the University of Pennsylvania were recognized for developing a therapy for inherited retinal degeneration that became the first gene therapy approved by the Food and Drug Administration for a genetic disease.
• Another prize went to Stuart Orkin, a physician at Harvard Medical School and Boston Children’s Hospital; and to Swee Lay Thein at the National Heart, Lung and Blood Institute for elucidating the mechanism driving the switch from fetal to adult hemoglobin and validating it as a therapeutic target for sickle-cell disease and beta-thalassemia.
• Rosa Rademakers of the Mayo Clinic and Bryan Traynor of the National Institute on Aging won the third prize in the life sciences for discovering the most common genetic cause of ALS and frontotemporal dementia.

Frank Merle of the Institut des Hautes Études Scientifiques in Paris was awarded this year’s prize in mathematics for achieving breakthroughs in nonlinear evolution equations. His work could have implications from aeronautical engineering and safety to astrophysics.

For his part, Hertzog doesn’t intend to rest on his laurels. Even as the Muon g-2 Collaboration is winding down, he has joined the team for another particle physics experiment called PIONEER. That experiment will probe inconsistencies between the Standard Model and observations of pion decay. As was the case with the Muon g-2 experiments, there’s a chance that PIONEER could point the way to physics beyond the Standard Model.

“This is a stock market golden opportunity,” Hertzog said. “That’s how I look at it.”

The Breakthrough Prize website has the full list of this year’s honorees, including the winners of New Horizons Prizes for early-career physicists and mathematicians, Maryam Mirzakhani New Frontiers Prizes for women mathematicians and the inaugural Vera Rubin New Frontiers Prize for women physicists. The recorded awards show is due to air at noon PT on April 26 via YouTube.

Hertzog and University of Bern physicist Martin Hoferichter review the results of the Muon g-2 experiments in a preprint paper titled “The Anomalous Magnetic Moment of the Muon: Status and Perspectives.”