A muon experiment conducted at Fermilab in the United States found that the “cousins” of these electrons seem to be interacting with particles or natural forces unknown to science. The discovery cannot be 100% confirmed, but the chance of accidental occurrence is only a fraction of 40,000 (1).
This wednesday First result experimental Meson g-2 At Fermi National Laboratory (Fermilab) And was surprised to find that the elementary particles are called meson Exhibit in ways that the best theories in the field cannot predict: Standard Model of Particle Physics.
This may imply that exciting new physics still exists.The meson can act as a window to the subatomic world and may interact with it Undiscovered particles or forces. So far, people have known gravity, electromagnetic force, strong force and weak force, but it may be one-fifth.
This major achievement was also published in the magazine Medical letter, This technique performed with unprecedented precision and confirmed the difference that caused researchers for two decades.
He emphasized: “Today is an extraordinary day, and not only we but the entire international physics community have been looking forward to it for a long time.” Graziano VenanzoniCo-spokesperson and physicist of the Muon g-2 experiment at the National Institute of Nuclear Physics in Italy, he emphasized the important role of young researchers in this discovery.
Oscillation of mesons, “cousins” of electrons
The mass of a meson is about 200 times that of its “cousin” electron. When cosmic rays hit the earth’s atmosphere, muons are naturally produced, and the particle accelerator at Fermilab can produce muons in large numbers. Like electrons, they act like small magnets inside.
In a strong magnetic field, the direction of the meson magnet is such that Movement dAnd precession, It swings like the axis of a top. The force of the internal magnet determines the precession speed of the particle in the external magnetic field and is described by a number that physicists call. Factor g. This number can be calculated very accurately.
When mesons circulate in the Muon g-2 magnet, they also interact with Quantum foam A collection of subatomic particles that appear and disappear. The interaction with these short-lived particles affects the value of the g factor, causing the precession of the meson to accelerate or decelerate very slowly.
The standard model predicts this so-called Abnormal magnetic moment Extremely high precision. However, if the quantum foam contains other forces or particles that are not considered in the model, the g-factor of the meson will be further modified, which seems to have happened.
He explained: “The quantity we measure reflects the interaction of mesons with all other things in the universe, but when theorists use all known forces and particles in the Standard Model to calculate the same quantity, we won’t get the same quantity. answer.” Renee FatemiA physicist at the University of Kentucky was responsible for the simulation of the experiment. “Therefore, this strong evidence shows that the muon is sensitive to things that do not exist in our best theory.”
Previous experiment Meson g-2,in Brookhaven National Laboratory (Also from the U.S. Department of Energy) and ended in 2001, this sign has shown that the behavior of mesons does not conform to the standard model.Now, the new measurement value in Fermilab is very consistent with the value in Brookhaven and is in line with The most accurate measurement So far.
Specifically, the acceptable theoretical value of the g factor of the muon is 2.00233183620, and its abnormal magnetic moment is 0.00116591810. However, the new experimental results announced this week by Muon g-2 are g-factor 2.00233184122 and abnormal magnetic moment 0.00116592061.
One in 40,000 chance
The difference seems to be small, but the combined data of Fermilab and Brookhaven is different from the theoretical value or the theoretical standard deviation 4.2 Sigma, Slightly lower than the 5 sigma required by scientists to confirm a real discovery. Researchers say this is still convincing evidence of new physics. The result is that the probability of statistical fluctuation is about 40,000.
The first result of Fermilab’s Muon g-2 experiment confirmed an experiment conducted at Brookhaven National Laboratory two decades ago. Both show strong evidence that mesons deviate from the predictions of the Standard Model of particle physics. / Ryan Postel, Fermilab / Muon g-2 cooperation
The Fermilab experiment reused the main components of Brookhaven, Superconducting magnetic storage ring 15 meters in diameter. In the Muon g-2 facility, a beam of muons is sent to the ring, where they circulate thousands of times at a speed close to the speed of light, and a detector covering it can determine the precession speed of the muons.
In the first year of operation (2018), the data collected by Muon g-2 is more than the sum of all previous experiments on the μgg factor.This collaboration was jointly completed by more than 200 scientists from 35 institutions in seven countries/regions, and analyzed Over 8 billion μs From his Primer Run Or the execution stage.
The scientist emphasized: “20 years have passed since the Brookhaven experiment ended, and this mystery has finally been solved, which is really gratifying.” Chris Polly, He used to be a student of the old experiment and is now a joint spokesperson for the current experiment.
Expectations for future Muon g-2 data
Analysis of the second and third data Run de Muon g-2 is already in progress, the fourth phase is also in progress, and the fifth phase is being planned. Combining the results of these five runs will provide scientists with a more accurate measurement of muon swings, thereby revealing with greater certainty whether the new physics is indeed hidden in the quantum foam.
“So far we have Analyze less than 6% of the data “The experiment will eventually be collected,” said Polly, like her colleague, and she looked forward to what might happen. Two years”.