Peering down a row of magnets causing the particle storage ring at Fermilab’s Muon g-2 experiment. The outcomes have theoretical physicists around the globe anxiously resolving concepts for descriptions. Credit: Photo by Cindy Arnold/Fermilab
Experiment opens field for brand-new physics, state Fermilab, UChicago researchers.
The news that muons have a little additional wiggle in their action sent out word buzzing around the globe this spring.
The Muon g-2 experiment hosted at Fermi National Accelerator Laboratory revealed on April 7 that they had actually determined a particle called a muon acting somewhat in a different way than anticipated in their huge accelerator. It was the very first unanticipated news in particle physics in years.
Everyone’s delighted, however couple of more so than the researchers whose task it is to spitball theories about how deep space is created. For these theorists, the statement has them cleaning off old theories and hypothesizing on brand-new ones.
“To a lot of us, it looks like and smells like new physics,” stated Prof. Dan Hooper. “It may be that one day we look back at this and this result is seen as a herald.”
Gordan Krnjaic, a fellow theoretical physicist, concurred: “It’s a great time to be a speculator.”
The 2 researchers are connected with the University of Chicago and Fermilab; neither worked straight on the Muon g-2 experiment, however both were elated by the outcomes. To them, these findings might be an idea that points the method to deciphering the last secrets of particle physics—and with it, our understanding of deep space as a whole.
The Muon g-2 ring beings in its detector hall in the middle of electronic devices racks, the muon beamline, and other devices. This excellent experiment runs at unfavorable 450 degrees Fahrenheit and research studies the precession, or “wobble,” of particles called muons as they take a trip through the electromagnetic field. Credit: Reidar Hahn/Fermilab
Setting the Standard
The issue was that whatever was going as anticipated.
Based on century-old experiments and theories returning to the days of Albert Einstein’s early research study, researchers have actually strategized a theory of how deep space—from its tiniest particles to its biggest forces—is created. This description, called the Standard Model, does a respectable task of linking the dots. But there are a couple of holes—things we’ve seen in deep space that aren’t represented in the design, like dark matter.
No issue, researchers believed. They developed larger experiments, like the Large Hadron Collider in Europe, to examine the most basic homes of particles, sure that this would yield ideas. But even as they looked more deeply, absolutely nothing they discovered appeared out of action with the Standard Model. Without brand-new opportunities to examine, researchers had no concept where and how to try to find descriptions for the inconsistencies like dark matter.
Then, lastly, the Muon g-2 experiment results can be found in from Fermilab (which is connected with the University of Chicago). The experiment reported a small distinction in between how muons need to act according to the Standard Model, and what they were really doing inside the huge accelerator.
What is a muon, and how does the Muon g-2 experiment work? Fermilab researchers describe the significance of the outcome.
Murmurs broke out around the globe, and the minds of Hooper, Krnjaic and their coworkers in theoretical physics started to race. Almost any description for a brand-new wrinkle in particle physics would have extensive ramifications for the history of deep space.
That’s due to the fact that the smallest particles impact the biggest forces in deep space. The minute distinctions in the masses of each particle impact the manner in which deep space broadened and developed after the Big Bang. In turn, that impacts whatever from how galaxies are held together down to the nature of matter itself. That’s why researchers wish to specifically determine how the butterfly flapped its wings.
The most likely suspects
So far, there are 3 primary possible descriptions for the Muon g-2 results—if it is undoubtedly brand-new physics and not a mistake.
One is a theory referred to as “supersymmetry,” which was extremely trendy in the early 2000s, Hooper stated. Supersymmetry recommends that that each subatomic particle has a partner particle. It’s appealing to physicists due to the fact that it’s an overarching theory that describes numerous inconsistencies, consisting of dark matter; however the Large Hadron Collider hasn’t seen any proof for these additional particles. Yet.
Another possibility is that some undiscovered, reasonably heavy kind of matter communicates highly with muons.
Finally, there might likewise exist some other type of unique light particles, yet undiscovered, that connect weakly with muons and trigger the wobble. Krnjaic and Hooper composed a paper setting out what such a light particle, which they called “Z prime,” might imply for deep space.
“These particles would have to have existed since the Big Bang, and that would mean other implications—for example, they could have an impact on how fast the universe was expanding in its first few moments,” Krnjaic stated.
That might dovetail with another secret that researchers are considering, called the Hubble consistent. That number is expected to suggest how quick deep space is broadening, however it differs somewhat according to which method you determine it—a disparity which might suggest a missing out on piece in our understanding.
Almost any description for a brand-new wrinkle in particle physics would have extensive ramifications for the history of deep space.
There are other, further-out possibilities, such as that the muons are being bumped by particles winking in and out of presence from other measurements. (“One thing particle physicists are rarely accused of is a lack of creativity,” stated Hooper.)
But the researchers stated it’s important not to dismiss theories out of hand, no matter how wild they might sound.
“We don’t want to overlook something just because it sounded weird,” stated Hooper. “We’re constantly trying to shake the trees to get every idea we can out there. We want to hunt this down everywhere it could be hiding.”
Sigma actions
The primary step, nevertheless, is to verify that the Muon g-2 result is true. Scientists have a system to inform whether the outcomes of an experiment are genuine and not simply a blip in the information. The result revealed in April reached 4.2 sigma; the standard that indicates it’s likely real is 5 sigma.
“If it’s really new physics, we’ll be much closer to knowing in a year or two,” stated Hooper. The Muon g-2 experiment has a lot more information to sort through. Meanwhile, the outcomes of some extremely complex theoretical computations—so complicated that even the most effective supercomputers on the planet requirement to chew on them for months to years—need to be boiling down the pike.
Those results, if they get to a 5 sigma self-confidence level, will point researchers where to go next. For example, Krnjaic assisted propose a Fermilab program called M3 that might narrow the possibilities by shooting a beam of muons at a metal target—determining the energy prior to and after the muons struck. Those results might suggest the existence of a brand-new particle.
Meanwhile, at the French-Swiss border, the Large Hadron Collider is arranged to update to a greater luminosity that will produce more accidents. New proof for particles or other phenomena might appear in their information.
All this enjoyment over a wobble may look like an overreaction. But small inconsistencies can, and have, caused huge shakeups. Back in the 1850s, astronomers making measurements of Mercury’s orbit saw it was off a little from what Newton’s theory of gravity would forecast. “That anomaly, along with other evidence, eventually led us to the theory of general relativity,” stated Hooper.
“No one knew what it was about, but it got people thinking and experimenting. My hope is that one day we’ll look back at this muon result the same way.”
References:
“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
“Magnetic-field measurement and analysis for the Muon g – 2 Experiment at Fermilab” by T. Albahri et al. (The Muon g-2 Collaboration), 7 April 2021, Physical Review A.
DOI: 10.1103/PhysRevA.103.042208
