Muons rotate while rotating in this closed laboratory circular accelerator, like a racing car that constantly turns

The potential gap in particle physicists' understanding of fundamental forces seems more realistic. New measurements confirm fast subatomic particle called muon may be slightly more magnetic than theory predicts, reported this week a team of over 200 physicists. little anomaly – only 25 parts per billion – is a welcome threat to the dominant theory of particle physicists, the standard model, that long ago explained everything they saw in atomic breakers and left them eager for something new to solve the mystery

«For years 1970, we are looking for a crack in the standard model», said Alexei Petrov, theorist at Wayne State University. «It could be Hulkin Sally Dawson, a theorist from Brookhaven National Laboratory, who noticed that the result was still not final. “It does nothing to our understanding of physics other than to say that we have to wait a little longer to see if it is real.”

For decades, physicists measure muon magnetism, which is a heavier and unstable cousin of the electron, which behaves like a small magnetic bar. They place muons in a vertical magnetic field that causes them to rotate horizontally like small compass needles. How often muons rotate reveals how magnetic they are. Which could in principle refer to new particles, even those that are too big to be destroyed in an atom smasher like the Large Hadron Collider in Europe

This is due to quantum uncertainty, because muons are in a fog of other particles and antiparticles that leak and disappear from existence. These particles «virtual» cannot be observed directly, but they can influence the properties of muons which predict quantum mechanics and Albert's theory of special relativity. Einstein thinks the muon must have some fundamental magnetism. The usual standard modular particles orbiting the muon increase the magnetism by approximately 10% and the unknown particles lurking in a vacuum can add another unexpected increase in change

In 2001, researchers reported in the Muon g-2 experiment, then in Brookhaven, that the muon was magnetic with more contact than expected by the standard model. The gap was only about 2,5 times the common theoretical and experimental uncertainty. is far from being the standard of physicists to claim the discovery: five times the total uncertainty but a bewildering allusion of new molecules out of reach

Two measurements found the same additional magnetism in the muon, probably an indication of new unknown particles.

So, in 2013, the researchers conducted the experiment at the Fermi National Accelerator Laboratory (Fermilab) in Illinois, where they were able to obtain purer beams of muons when the redesigned experiment began to take data in 2018. The difference in muons between the experiment and the theoretical results increased to 37 times the overall uncertainty

Now, the g-2 team released the first result of the revamped experiment, using one year data and the new result is almost completely in agreement with the old result, as announced today at a seminar at Fermilab The consensus shows that the old result was neither a statistical chance nor the product of certain flaws not discovered in the experiment, this Chris Polley, Fermilab physicist and spokesperson for the G-2 team, “Since I was a graduate student in the Brookhaven experiment, it was truly an overwhelming sense of relief for me », this

Ensemble, new and old findings widen the difference with the standard model prediction to 4 both experimental and theoretical errors. This is still insufficient to claim a specific discovery, but in a field where signals similar to new physics appear and disappear, Muon magnetism has remained an almost singular mystery, dit graham. Krebs, theoretical researcher at the University of Oregon “Nothing else is characteristic of the whole community.” Remember we also have to deal with this. “

The whole g-2 team shared a moment of truth when the experimenters first revealed the new result for themselves on 25 February. The experiment consists of measuring the speed at which the muons rotate with extreme precision and refraining from subconsciously directing the to the value they prefer. The experimenters relied on An Hour that goes by with a secret frequency known only to two people, who only cooperate at the end of the analysis, opened the envelopes containing the secret frequency – during a Zoom meeting due to COVID-19 restrictions, says Hannah Benny, graduate student and team member at the University of Washington, Seattle: «It definitely was.« There is an atmosphere of intense tension. »In a few seconds, she says, the researchers used a secret reluctance to find out that the new result matches the old.

Petrov says immediate responses to new discovery will likely be twofold. First, with confirmation of empirical value, physicists are likely to question the theoretical estimate. From 2017, more than 130 theorists met in a series of workshops to reach consensus on the standard model prediction, which they published in November 2020 But Petrov says the math is a “complex mixture” which uses a variety of methods – including extrapolation from the collider results – to calculate different types of Standard Model particles flowing in and out of space. Theorists will now redouble their efforts to verify the values ​​of consensus and develop calculation methods that allow them to be explained by first principles, this Petrov

Of course, others will begin to invent new theories that go beyond the Standard Model and explain the additional magnetism of muons Petrov predicts that «it will be a field day for theorists». Their speculations may be premature, car g- 2 experimenters always take data and hope to reduce experimental uncertainty by a percentage of 75% in a few years so that the gap can be closed but, if the muon really indicates the presence of something new, many theorists will be eager to start

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Physique, Muon g-2, Fermilab, Muon, The physics behind the standard model, the particles

News – THAT – The mystery of the particles deepens, as physicists claim muon is more magnetic than expected


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