The result, physicists say, suggests that there are forms of matter and energy vital to the nature and evolution of the cosmos that are not yet known to science. “This is our Mars rover landing moment,” said Chris Polly, a physicist at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia, Ill., who has been working toward this finding for most of his career.
The particle célèbre is the muon, which is akin to an electron but far heavier, and is an integral element of the cosmos. Dr. Polly and his colleagues — an international team of 200 physicists from seven countries — found that muons did not behave as predicted when shot through an intense magnetic field at Fermilab. The aberrant behavior poses a firm challenge to the Standard Model, the suite of equations that enumerates the fundamental particles in the universe (17, at last count) and how they interact. “This is strong evidence that the muon is sensitive to something that is not in our best theory,” said Renee Fatemi, a physicist at the University of Kentucky.
The results, the first from an experiment called Muon g-2, agreed with similar experiments at the Brookhaven National Laboratory in 2001 that have teased physicists ever since. At a virtual seminar and news conference on Wednesday, Dr. Polly pointed to a graph displaying white space where the Fermilab findings deviated from the theoretical prediction. “We can say with fairly high confidence, there must be something contributing to this white space,” he said. “What monsters might be lurking there?”
“Today is an extraordinary day, long awaited not only by us but by the whole international physics community,” Graziano Venanzoni, a spokesman for the collaboration and a physicist at the Italian National Institute for Nuclear Physics, said in a statement issued by Fermilab.
The measurements have about one chance in 40,000 of being a fluke, the scientists reported, well short of the gold standard needed to claim an official discovery by physics standards. Promising signals disappear all the time in science, but more data are on the way. Wednesday’s results represent only 6 percent of the total data the muon experiment is expected to garner in the coming years. Muons are an unlikely particle to hold center stage in physics. Called “fat electrons,” they resemble the familiar elementary particles that power our batteries, lights and computers and whiz around the nuclei of atoms; they have a negative electrical charge, and they have a property called spin, which makes them behave like tiny magnets.
But they are 207 times as massive as their better-known cousins. They are also unstable, decaying radioactively into electrons and super-lightweight particles called neutrinos in 2.2 millionths of a second. What part muons play in the overall pattern of the cosmos is still a puzzle. “Who ordered that?” the Columbia University physicist Rabi said when they were first discovered in 1936. Nowadays muons are produced copiously at places like the Large Hadron Collider when more ordinary particles are crashed together at high energies.
Overbye is a science reporter with NYT©2021
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