Muon g-2 experiment results point at new physics.

Pretty wild stuff, forget the centripetal forces, there’s some new physics in the offing. Or at least some readjustments.

First results from Fermilab's Muon g-2 experiment strengthen evidence of new physics

CHICAGO, April 7, 2021 /CNW/ – 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. …

As there isn’t universal agreement about the predicted value of a muon’s g-factor I think the current level of excitement is unwarranted.


But not without precedent. ?

I agree with you, but I know there are some armchair physicists around here sometimes, and I figured I’d take the story for a spin, see if starts any conversation.


I agree with you, but I know there are some armchair physicists around here sometimes, and I figured I’d take the story for a spin, see if starts any conversation.
I wish that the rendering was more naturally presented. These colors looked absolutely artificial and prima facie false.


“But not without precedent.” With such a lot of taxpayers’ money going into these experiments I suppose the public need to be as entertained as much as possible. Wake me up when the 8th, 9th and 10th decimal figures have finally been sorted out.

I’ve spent years trying to get physicists to discuss more fundamental matters which would cost virtually nothing.


I’m an armchair physicist and honestly I gave up. On the Discovery feed on my phone, just skimming the headlines, “Muons point to revolution in physics”, x3, then “Not so fast, Muon might not lead to new physics”. I mean I get it, that’s what makes science successful, the back and forth. But geeze, one minute warp travel is right on the horizon, the next minute scientist X says no, it’s actually the exact opposite.

And I see it so many times about so many topics, not just physics. I’m starting to wonder if what’s really happening is scientists know they need grants, but no one’s interested in the little stuff, so they exclaim “we’re on the brink of something incredible…money please”.

Well sure, more study is needed. Same as it ever was.

I bumped into this attempt at putting this new finding into perspective.

I’m trying to figure out if the video is informative or simply cute because of how difficult it is to explain it to us regular mortals.

But she doesn’t mention the BMW calculations, as in “This difference could signal new particles waiting to be discovered. But on the same day, 14 theorists from the Budapest-Marseille-Wuppertal (BMW) collective of scientists published an article that suggests the calculation is wrong. The value would be much closer to the experimental result, which practically eliminates the discrepancy found by the team of the Múon g-2 experiment.”

ht tps://ww

I don’t know how to insert a link on this forum so it just stays as a web address, so I’ve included a couple of blank spaces.

Thanks for that link.

Physics threatened: the muon may not be so magnetic after all By Leonard Manson - April 17, 2021

Interesting background

Understanding the muon
The heavier and unstable cousin of the electron acts as a tiny magnet, which makes its magnetism a means for detecting evidence of new particles. Therefore, quantum mechanics and relativity require the muon to have a certain basic magnetism. Thanks to quantum uncertainty, particles and antiparticles also exist and constantly cease to exist around the muon. These “virtual” particles, although they cannot be observed directly, can affect the properties of the muon, including its magnetism. …

Theorists can also try to perform brute force QCD calculations on supercomputers – if they model the space-time continuum as a network of discrete points occupied by quarks and particles called gluons, which transmit the force. And, in fact, twelve years ago, theorists showed that this “QCD network” technique was able to calculate the masses of the proton and neutron, the hadrons. Several groups of scientists have also applied the network to the muon magnetism, albeit with considerable uncertainty.

Now, after millions of hours of research on the processor at the Jülich Research Center in Germany, another group of scientists has produced a network calculation of the hadronic vacuum polarization and a value for the muon magnetism that accurately rivals the value of the standard model consensus: the new result is only part per billion below the experimental value, as the team recently reported to the journal Nature – which is hardly a discrepancy.


I think this is a helpful extract from Quanta magazine:

"However, even as many particle physicists are likely to be celebrating — and racing to propose new ideas that could explain the discrepancy — a paper published today in the journal Nature casts the new muon measurement in a dramatically duller light. The paper, which appeared just as the Fermilab team unveiled its new measurement, suggests that the muon’s measured wobbliness is exactly what the Standard Model predicts.

In the paper, a team of theorists known as BMW present a state-of-the-art supercomputer calculation of the most uncertain term that goes into the Standard Model prediction of the muon’s magnetic moment. BMW calculates this term to be considerably larger than the value adopted last year by the consortium, a group known as the Theory Initiative. BMW’s larger term leads to a larger overall predicted value of the muon’s magnetic moment, bringing the prediction in line with the measurements.

If the new calculation is correct, then physicists may have spent 20 years chasing a ghost. But the Theory Initiative’s prediction relied on a different calculational approach that has been honed over decades, and it could well be right. In that case, Fermilab’s new measurement constitutes the most exciting result in particle physics in years.

“This is a very sensitive and interesting situation,” said Zoltan Fodor, a theoretical particle physicist at Pennsylvania State University who is part of the BMW team.

BMW’s calculation itself is not breaking news; the paper first appeared as a preprint last year. Aida El-Khadra, a particle theorist at the University of Illinois who co-organized the Theory Initiative, explained that the BMW calculation should be taken seriously, but that it wasn’t factored into the Theory Initiative’s overall prediction because it still needed vetting. If other groups independently verify BMW’s calculation, the Theory Initiative will integrate it into its next assessment.

Dominik Stöckinger, a theorist at the Technical University of Dresden who participated in the Theory Initiative and is a member of the Fermilab Muon g-2 team, said the BMW result creates “an unclear status.” Physicists can’t say whether exotic new particles are pushing on muons until they agree about the effects of the 17 Standard Model particles they already know about.

Regardless, there’s plenty of reason for optimism: Researchers emphasize that even if BMW is right, the puzzling gulf between the two calculations could itself point to new physics. But for the moment, the past 20 years of conflict between theory and experiment appear to have been replaced by something even more unexpected: a battle of theory versus theory."

But for the moment, the past 20 years of conflict between theory and experiment appear to have been replaced by something even more unexpected: a battle of theory versus theory.”
Translation, more research needed. ?

Yep, but I think it’ll be a long moment.