The results of one of the most anticipated experiments in particle physics are in, and it may be about to fulfill every researcher’s wildest dreams: they might break physics as we know it.
Evidence from the Fermi National Accelerator Laboratory near Chicago appears to indicate a miniscule subatomic particle known as the muon much more shaky than the theory predicts it should be. According to physicists, the best explanation is that the muon is stimulated by types of matter and energy that are completely unknown to physics.
If the results are true, the discovery represents a breakthrough in particle physics of a kind not seen for 50 years, when the dominant theory for explaining subatomic particles was first developed. The tiny tiny pendulum of the muon – created by the interaction of its intrinsic magnetic field, or magnetic moment, with an external magnetic field – can shake the foundations of science.
“Today is an extraordinary day, not only by us, but also by the entire international physics community,” said Graziano Venanzoni, co-spokesman for the Muon. g-2 experiment and physicist at the Italian National Institute of Nuclear Physics, said in a statement.
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Sometimes known as ‘fat electrons’, muons are similar to their more famous cousins, but are 200 times heavier and radioactively unstable – they decay in just one millionth of a second into electrons and small, ghostly, chargeless particles known as neutrinos . Muons also have a property called spin, which in combination with their charge causes them to act as if they were small magnets, causing them to wobble like small gyroscopes when plugged into a magnetic field.
But today’s results, which stem from an experiment in which physicists sent moons whispering around a superconducting magnetic ring, apparently show that the muon is wobbling much more than it should be. The only explanation, according to the scientists, is the existence of particles that are not yet offset by the set of equations that explain all subatomic particles, called the standard model – which has remained unchanged since the mid-1970s. The idea is that those exotic particles and the accompanying energies should push and pull the muzzles into the ring.
The Fermilab researchers are fairly confident that what they saw (the extra wobble) was a real phenomenon and not a statistical happiness. They place a number on the confidence of ‘4.2 sigma’, which is incredibly close to the 5 sigma threshold at which particle physicists declare an important discovery. (A 5-sigma result indicates that the chance is 1 in 3.5 million that this happened by chance.)
“This quantity we measure reflects the interactions of the muon with all the others in the universe. But when the theorists calculate the same quantity, using all the known forces and particles in the standard model, we do not get the same answer,” Renee Fatemi, a physicist at the University of Kentucky and the simulation manager of the Muon g-2 experiment, said in a statement. “This is strong evidence that the muon is sensitive to something that is not in our best theory.”
A competitive calculation made by a separate group and published in the magazine on Wednesday (April 7) Earth can rob the pendulum of its meaning. According to this team’s calculations, which give a much greater value to the most uncertain term in the equation that predicts the muon’s rocking motion, the experimental results are completely consistent with predictions. Twenty years of particle hunting could have all been in vain.
“If our calculations are correct and the new measurements do not change the story, it seems that we do not need any new physics to explain the magnetic moment of the muon. It follows the rules of the standard model,” said Zoltan Fodor, a professor of physics at Penn State and a leader of the research team that published the Nature article, said in a statement.
But Fodor added that since the group’s forecast was based on a totally different calculation with very different assumptions, their results were far from a complete deal. “Our finding means that there is tension between the previous theoretical results and our new ones. This difference must be understood,” he said. “In addition, the new experimental results may be close to the old ones or closer to the previous theoretical calculations. We have many years of excitement ahead of us.”
In essence, physicists will not be able to finally say whether brand new particles are tugging at their muzzles until they can agree on exactly how the 17 existing standard model particles also interact with muons. Until one theory wins, physics is left in the balance.
Originally published on Live Science.