A new discovery around an elementary particle indicates that the quantum world is much more extensive than we currently know: hitherto unknown particles are emerging from the void, mortally beating the Standard Model, the most complete theoretical framework we have to explain the universe.
Last month, researchers from the European Organization for Nuclear Research (CERN) discovered a major fissure in the Standard Model of particle physics that, if confirmed, would herald a New Physics of still imprecise dimensions.
Less than a month later, the North American high-energy physics laboratory Fermilab, which has the second most powerful particle accelerator in the world, nails the final nail: it confirms the need to reconstruct the model that describes all elementary particles.
The Standard Model, developed almost 50 years ago, has always shown its shortcomings: it has failed to explain everything, particularly fundamental physical constants, dark matter or energy. For this reason, it is considered a model that needs to be perfected.
Scientists have long been exploring an even more fundamental theory, which they have called New Physics, to explain the anomalies detected in the Standard Model.
CERN discovered an unexpected behavior in a subatomic particle called a background quark, also known as a beauty quark: it could be the result of its interaction with another unknown subatomic particle that exerts an imprecise force on that particle.
Final thrust If that discovery has already seriously injured the Standard Model, what Fermilab has observed adds the final touch to this description of the world: it will have an impact similar to the discovery of the Higgs boson, which explained the origin of the mass it gives it shapes the universe and left the door open to the New Physics.
The first results of the Muon g-2 experiment at Fermilab show fundamental particles called muons that behave in a way not predicted by the Standard Model.
It is, as explained in a statement , a historic result, performed with unprecedented precision, confirming the discrepancy that has been eating away at researchers for decades.
Muon g −2 is a particle physics experiment that measures the anomalous magnetic dipole moment of the muon: the result of that measurement has provided the missing evidence for the existence of completely new particles not collected in the Standard Model.
It indicates that the virtual soup of particles that interacts with all forms of matter, has mysterious and unidentified ingredients to which muons are especially sensitive.
A muon is about 200 times more massive than its cousin, the electron. Muons are produced naturally when cosmic rays strike Earth’s atmosphere, and Fermilab’s particle accelerators can produce them in large quantities.
Magnetic moment Like electrons, muons act as if they have a small internal magnet. In a strong magnetic field, the direction of the muon magnet precesses (precession is the motion associated with changing direction in space) or wobbles, much like the axis of a spinning top.
The strength of the internal magnet determines the speed at which the muon precesses in an external magnetic field. That force from the internal magnet is called the magnetic moment.
The muon’s magnetic moment was first measured in 2001 at Brookhaven National Laboratory in New York, and it was found to be larger than predicted by the Standard Model.
Physicists then thought that interaction with unknown particles, perhaps contemplated by a theory called supersymmetry, could have caused this anomaly.
The new measurement of the Muon g-2 experiment at Fermilab is in strong agreement with the value found at Brookhaven and shows that the Standard Model alone cannot explain it. It is convincing proof of the New Physics, its discoverers emphasize.
None of the experiments, both by Brookhaven and Fermilab, is still considered an official discovery, because there is a small possibility that the results obtained are due to statistical errors.
Only 6% of the data that Fermilab will collect around the muon’s magnetic moment have been analyzed so far, and while this is considered more than enough to challenge the Standard Model, the analyzes will continue.
In fact, data analysis for the second and third runs of the experiment is underway, the fourth run is being organized, and even a fifth run is planned.
Combining the results of the five experiments will give scientists an even more precise measure of the muon oscillation, revealing with greater certainty whether the New Physics lurks within the quantum foam.
Last word? However, French scientists warn in the journal Nature that the Standard Model may not have said the last word yet: an independent calculation method concludes that the anomaly detected in the magnetic moment of the muon is less than that established in the measurements.
This “anomaly anomaly” needs to be confirmed by other teams, but French scientists hope to get a new prediction that is accurate enough to decide the fate of the Standard Model in the next few years.