Scientists are getting closer to identifying a new force in nature after observing the peculiar “wobble” of a subatomic particle.
The experts whizzed tiny muons, which resemble electrons, through a 50-foot-diameter ring at the US Department of Energy’s Fermilab in Batavia, Illinois.
Measurements of the muon’s magnetic “wobbling” cannot be explained by the Standard Model of particle physics – possibly pointing to an unknown fifth force.
Because muons form naturally when cosmic rays hit Earth’s atmosphere, these findings could change the way we think the universe works.
The results support previous findings from 2021, but comprise more than four times the amount of data analyzed, supporting the claim of “new physics”.
The Muon g-2 ring is housed in its detector hall at the US Department of Energy’s Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois
What are muons?
Muons are negatively charged fundamental subatomic particles, similar to electrons but about 200 times more massive.
Importantly, muons are also magnetic and wobble when spinning in the presence of a strong magnetic field.
Their magnetic moment describes how strong their inherent magnets are and how strong a surrounding magnetic field causes the particles to wobble or “precess”.
Fermilab scientists detailed their work in a research report filed Thursday with the journal Physical Review Letters.
“We’re looking for an indication that the muon is interacting with something we don’t know about,” said study author Brendan Casey, senior scientist at Fermilab.
“It could be anything – new particles, new forces, new dimensions, new features of space-time, anything.”
Casey theorizes the results point to a “new property of spacetime,” or a violation of Lorentz invariance, a principle that says the laws of physics are the same everywhere.
“That would be crazy and revolutionary,” he said.
For centuries scientists have tried to figure out what happens at the “subatomic” level, involving particles smaller than atoms.
Atoms, the basic units of matter that we can see and touch, combine to form molecules (which in turn form solids, gases, and liquids).
How the universe works at this fundamental subatomic level is what physicists describe with a theory known as the Standard Model, which was developed in the early 1970s.
It suggests that everything in the universe is made up of a few basic building blocks called elementary particles, governed by four forces – the strong force, the weak force, the electromagnetic force, and the gravitational force.
The muons, which resemble electrons, orbit thousands of times at nearly the speed of light to measure how they “wiggle” over time.
Dubbed the Muon g-2 experiment, as the particles moved along the 50-foot magnetic track, they varied 0.1 percent from the standard model that had been used for 50 years
Over the course of the 20th century, it established itself as a proven physical theory and has accurately predicted a large number of phenomena.
However, the model fails to explain some of the deepest mysteries of modern physics, including the composition of dark matter and the imbalance of matter and antimatter in the universe.
To solve some of these mysteries, researchers have looked for particles that behave differently than would be expected in the Standard Model.
The most recent experiments at Fermilab, dubbed Muon g-2, studied the wobbling of muons as they move through a magnetic field.
The muon (pronounced “mew-on”) is a magnetic and negatively charged particle similar to its cousin, the electron, but 200 times more massive.
They are formed naturally when cosmic rays hit the Earth’s atmosphere.
Importantly, muons are also magnetic and wobble when spinning in the presence of a strong magnetic field.
Like the electron, the muon has a tiny inner magnet that causes it to wobble—or, technically speaking—to “precess” like the axis of a spinning top.
It measures the “magnetic moment” – the measure of the object’s tendency to align itself with a magnetic field
The Fermilab experiment – conducted in unimaginably cold temperatures of -268 °C (-450 °F) – shot beams of muons into the donut-shaped superconducting magnetic storage ring, which is 50 feet (15 meters) in diameter.
The muons orbit the ring thousands of times at nearly the speed of light to measure how they “wobble” over time.
As the muons fly around, they interact with other subatomic particles, which change their wobble like tiny “dance partners”.
Using detectors along the ring, scientists were able to determine how fast the muons were “precessing”.
Similar to the results in 2021, the rate of wobble measured in the experiment differed significantly from the rate predicted on the Standard Model.
The muon’s ‘magnetic moment’ – the measure of the object’s tendency to align itself with a magnetic field – as a function of the particle’s spin is represented by the letter g and should, according to theory, be slightly larger than 2.
However, the newly announced measurements found the magnetic moment is stronger by about 0.2 parts per million, a small but significant figure.
The new experiment reproduces and improves on an earlier experiment at Brookhaven National Laboratory in New York, whose 2006 results first suggested that the muon’s behavior differed from the Standard Model.
Subsequent measurements at Fermilab supported this result with greater certainty, but no more than the new results.
The 2021 results also showed unusual volatility, but the new results were based on a quadrupling of the data set, boosting confidence in the results.
The new experiment reproduces and improves on an earlier experiment at Brookhaven National Laboratory in New York
The team is still working to bring together three more years of data to enable a conclusive measurement of the muon’s so-called ‘magnetic moment’.
Ultimately, the results continue to point to a mysterious factor – possibly “unknown particles or forces” that could rival the importance of the 2012 discovery of the Higgs boson.
“With all these new findings, the result is still consistent with previous results, and that’s extremely exciting,” said study co-author Dr. Rebecca Chislett from University College London.
“The results further corroborate our team’s previous precise measurements of the muon’s anomalous magnetic moment, reaching unprecedented accuracy in testing the Standard Model and digging deeper into the subatomic world.”
EXPLAINED: THE STANDARD MODEL OF PHYSICS DESCRIBES THE BASIC STRUCTURE OF MATTER IN THE UNIVERSE
The theories and discoveries of thousands of physicists since the 1930s have led to remarkable discoveries about the fundamental structure of matter.
It turns out that everything in the universe is made up of a few basic building blocks called elementary particles, which are governed by four basic forces.
Our best understanding of how these particles and three of the forces are related is summarized in the Standard Model of particle physics.
All matter around us consists of elementary particles, the building blocks of matter.
These particles come in two basic types: quarks and leptons. Each consists of six particles connected in pairs or “generations”.
All stable matter in the universe consists of first-generation particles. All heavier particles quickly decay to the next most stable level.
There are also four basic forces at work in the universe: the strong force, the weak force, the electromagnetic force and the gravitational force. They work in different areas and have different strengths.
Gravity is the weakest, but has infinite range.
The electromagnetic force also has an infinite range, but is many times stronger than gravity.
The weak and strong forces act only over a very short range and are dominant only at the level of subatomic particles.
The Standard Model includes the electromagnetic, strong and weak forces and all their carrier particles and explains well how these forces act on all particles of matter.
However, the most familiar force in our everyday lives, gravity, is not part of the Standard Model, and fitting gravity comfortably into this framework has proven to be a difficult challenge.