Posted on 04/07/2021 12:22:28 PM PDT by Red Badger
The long-awaited first results from the Muon g-2 experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory show fundamental particles called muons behaving in a way that is not predicted by scientists’ best theory, the Standard Model of particle physics. This landmark result, made with unprecedented precision, confirms a discrepancy that has been gnawing at researchers for decades.
The strong evidence that muons deviate from the Standard Model calculation might hint at exciting new physics. Muons act as a window into the subatomic world and could be interacting with yet undiscovered particles or forces.
“Today is an extraordinary day, long awaited not only by us but by the whole international physics community,” said Graziano Venanzoni, co-spokesperson of the Muon g-2 experiment and physicist at the Italian National Institute for Nuclear Physics. “A large amount of credit goes to our young researchers who, with their talent, ideas and enthusiasm, have allowed us to achieve this incredible result.”
First results from the Muon g-2 experiment at Fermilab have strengthened evidence of new physics. The centerpiece of the experiment is a 50-foot-diameter superconducting magnetic storage ring, which sits in its detector hall amidst electronics racks, the muon beamline, and other equipment. This impressive experiment operates at negative 450 degrees Fahrenheit and studies the precession (or wobble) of muons as they travel through the magnetic field. Credit: Reidar Hahn, Fermilab
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A muon is about 200 times as massive as its cousin, the electron. Muons occur naturally when cosmic rays strike Earth’s atmosphere, and particle accelerators at Fermilab can produce them in large numbers. Like electrons, muons act as if they have a tiny internal magnet. In a strong magnetic field, the direction of the muon’s magnet precesses, or wobbles, much like the axis of a spinning top or gyroscope. The strength of the internal magnet determines the rate that the muon precesses in an external magnetic field and is described by a number that physicists call the g-factor. This number can be calculated with ultra-high precision.
As the muons circulate in the Muon g-2 magnet, they also interact with a quantum foam of subatomic particles popping in and out of existence. Interactions with these short-lived particles affect the value of the g-factor, causing the muons’ precession to speed up or slow down very slightly. The Standard Model predicts this so-called anomalous magnetic moment extremely precisely. But if the quantum foam contains additional forces or particles not accounted for by the Standard Model, that would tweak the muon g-factor further.
“This quantity we measure reflects the interactions of the muon with everything else in the universe. But when the theorists calculate the same quantity, using all of the known forces and particles in the Standard Model, we don’t get the same answer,” said Renee Fatemi, a physicist at the University of Kentucky and the simulations manager for the Muon g-2 experiment. “This is strong evidence that the muon is sensitive to something that is not in our best theory.”
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.
The accepted theoretical values for the muon are: g-factor: 2.00233183620(86) anomalous magnetic moment: 0.00116591810(43) [uncertainty in parentheses]
The new experimental world-average results announced by the Muon g-2 collaboration today are: g-factor: 2.00233184122(82) anomalous magnetic moment: 0.00116592061(41)
The combined results from Fermilab and Brookhaven show a difference with theory at a significance of 4.2 sigma, a little shy of the 5 sigma (or standard deviations) that scientists require to claim a discovery but still compelling evidence of new physics. The chance that the results are a statistical fluctuation is about 1 in 40,000.
The Fermilab experiment reuses the main component from the Brookhaven experiment, a 50-foot-diameter superconducting magnetic storage ring. In 2013, it was transported 3,200 miles by land and sea from Long Island to the Chicago suburbs, where scientists could take advantage of Fermilab’s particle accelerator and produce the most intense beam of muons in the United States. Over the next four years, researchers assembled the experiment; tuned and calibrated an incredibly uniform magnetic field; developed new techniques, instrumentation, and simulations; and thoroughly tested the entire system.
The Muon g-2 experiment sends a beam of muons into the storage ring, where they circulate thousands of times at nearly the speed of light. Detectors lining the ring allow scientists to determine how fast the muons are precessing.
In its first year of operation, in 2018, the Fermilab experiment collected more data than all prior muon g-factor experiments combined. With more than 200 scientists from 35 institutions in seven countries, the Muon g-2 collaboration has now finished analyzing the motion of more than 8 billion muons from that first run.
“After the 20 years that have passed since the Brookhaven experiment ended, it is so gratifying to finally be resolving this mystery,” said Fermilab scientist Chris Polly, who is a co-spokesperson for the current experiment and was a lead graduate student on the Brookhaven experiment.
Data analysis on the second and third runs of the experiment is under way, the fourth run is ongoing, and a fifth run is planned. Combining the results from all five runs will give scientists an even more precise measurement of the muon’s wobble, revealing with greater certainty whether new physics is hiding within the quantum foam.
“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,” Polly said.
“Pinning down the subtle behavior of muons is a remarkable achievement that will guide the search for physics beyond the Standard Model for years to come,” said Fermilab Deputy Director of Research Joe Lykken. “This is an exciting time for particle physics research, and Fermilab is at the forefront.”
Reference: “Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm” by B. Abi et al. (Muon g−2 Collaboration), 7 April 2021, Physical Review Letters. DOI: 10.1103/PhysRevLett.126.141801
The Muon g-2 experiment is supported by the Department of Energy (US); National Science Foundation (US); Istituto Nazionale di Fisica Nucleare (Italy); Science and Technology Facilities Council (UK); Royal Society (UK); European Union’s Horizon 2020; National Natural Science Foundation of China; MSIP, NRF and IBS-R017-D1 (Republic of Korea); and German Research Foundation (DFG).
Fermilab is America’s premier national laboratory for particle physics research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC.
The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.
[Editor’s Note: Today a different group of researchers announced very different results, concluding that the muon’s magnetic field aligns with the standard model of particle physics.]
gravitons?
Particle physicists are like very picky accountants. In every experiment the energy books must balance to the expected theoretically predicted value (within some inevitable measurement error) or they begin to think there’s a hidden accountant somewhere they don’t know about that is cooking the books.
This was the kind of problem that perplexed physicists at the turn of the 20th century and was called the “ultraviolet catastrophe” of radiating bodies. What finally emerged from this problem was quantum mechanics and QFT. Much of the modern world is now dependent on solid state devices that resulted from our understanding of these quantum effects.
The quantum foam is also known as the vacuum energy or dark energy and makes up 75% of the energy of the universe. If there is a way to tap some hidden account in this energy bank we might be able to control energies beyond our imagination in the future.
Wheels within wheels... and filled with eyes...
Oh wheel!!
The glueon research funding is currently stuck so the research is on hold.
They may discover that every time they record an anomaly, the event is preceded by the janitor placing his mop against the collider the night before.
I made B’s and it is Greek to me too. Anyway, I hope these folks have a great time with their Muons.
When Jesus comes back He can explain everything in ten minutes. After all, He created the whole shootin’ match.
Great thought. The Master can tell us about it.
Is quantum foam like primordial soup or do you have to add your own seasonings and whisk ‘til firm *-?
Maybe they will use moun theory to prevent spam robocalls on cell phones.
I understood about 40 words, but enough to ask timidly, can muon production be scaled and be used as a foundation for an antigravity or propulsion mechanism?
Muahahaha-ons
Need quantum foam energy storage battery so when matter and energy go in and out of existence we can have back up. Otherwise the world will end when quantum foam fizzles out.
YHWH.......................
So that's why it has a mumu on?
I got A’s in physics and I don’t understand it either. I don’t think physics went that deep in my school days, but I’m happy they’re happy, good for them.
What's the Standard Model Binary Cow say, half the time?
This article is about muontology..................
"But in the Latin declension, my point is still moot."
These virtual particles only appear to pop in and out of existence. Reality has more dimensions than the 3 we experience everyday. Most of the forces we experience are also limited to 3 dimensions so it seems that the 3 are all there is. This strange behavior is due to things which have those extra dimensions involved.
I’ll say it’s an extraordinary day. It’s my birthday. Now I’m officially old to enough for Medicare.
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