After twenty years, confirmation of research done in 2001 has been found that a tiny subatomic particle may be defying the best theory scientists have of how physics work, titled the Standard Model.
At the Department of Energy’s Fermilab in Batavia, Illinois, scientists sent a beam of muons into a huge 50-foot-wide storage ring controlled by superconducting magnets. Muons are roughly 200 times bigger than electrons and occur when cosmic rays strike Earth’s atmosphere.
Muons seem to have an internal magnet which wobbles, also known as “precesses,” like the axis of a top that spins. The rate of the precessing is determined by how strong the seeming internal magnet is. The muons circulating within the storage ring contact a quantum foam of subatomic particles that appear and disappear, thus slowing down or speeding up. That is called the “magnetic moment,” which is “represented in equations by a factor called g,” as The New York Times explained.
The Standard Model should be able to predict the “magnetic moment” with precision, but if additional forces or particles lie within the quantum foam that the Standard Model cannot explain, the muon’s g-factor would be affected.
“The predecessor experiment at DOE’s Brookhaven National Laboratory, which concluded in 2001, offered hints that the muon’s behavior disagreed with the Standard Model. The new measurement from the Muon g-2 experiment at Fermilab strongly agrees with the value found at Brookhaven and diverges from theory with the most precise measurement to date,” Fermilab stated.
In 2006, the final result of the 2001 research at the Brookhaven National Laboratory was announced, and there was a discrepancy with the Standard Model’s prediction. As Jennifer Ouellette of Ars Technica explained:
The muon’s measured magnet moment came in at a smaller value. Even more intriguing, that result was deemed a 3.7-sigma effect. (A signal’s strength is determined by the number of standard statistical deviations, or sigmas, from the expected background in the data, producing a telltale “bump.” This metric is often compared to a coin landing on heads several tosses in a row. A three-sigma result is a strong hint. The gold standard for claiming discovery is a five-sigma result, comparable to tossing 21 heads in a row, for example.)
She continued: “That said, three-sigma results, while tantalizing, pop up all the time in particle physics, and more often than not, they disappear once more data is added to the mix. So Fermilab revived the Muon g-2 experiment in hopes of either confirming or refuting the discrepancy once and for all.”
The latest results closely matched the results from Brookhaven: “Taken together, they boost the statistical significance to 4.2 sigma—teetering just on the verge of the threshold required for discovery,” Ouelette noted, adding, “That means there is only a 1 in 40,000 chance that this is due to a statistical fluctuation.”
Chris Polly, a physicist at the Fermi National Accelerator Laboratory who was a graduate student at Brookhaven and has been studying the issue for decades, stated, “This is our Mars rover landing moment. … After the 20 years that have passed since the Brookhaven experiment ended, it is so gratifying to finally be resolving this mystery.” He added, “So far we have analyzed less than 6% of the data that the experiment will eventually collect. Although these first results are telling us that there is an intriguing difference with the Standard Model, we will learn much more in the next couple of years.”
Renee Fatemi, a physicist at the University of Kentucky, echoed, “This is strong evidence that the muon is sensitive to something that is not in our best theory.”
Polly noted a graph showing white space where the latest results differed from the Standard Model, then said, “We can say with fairly high confidence there must be something contributing to this white space. What monsters might be lurking there?”