Seven years ago, massive magnets were moved more than 3,200 miles (5,150 km) across land and sea in the hopes of studying the particles in atoms known as miwons.
Muons are closely related to electrons, which orbit every atom and form a constituent of matter. Both electrons and muons have properties that are precisely predicted by our current best scientific theories that describe the subatomic, quantum world, the standard model of particle physics.
A whole generation of scientists made a great effort to measure these properties in detail in 2001. Experiments hinted that one of the Moun properties did not match the standard predicted model. But new studies are needed to confirm. Physicists moved part of the experiment to a new accelerator at Fermilab and began to acquire more information.
The new measurements have now confirmed preliminary results. This means that there may be new particles or forces that were not included in the standard model. If this is the case, the laws of physics will have to be revised and no one knows where it will lead.
The latest results come from international cooperation, which we are all part of. Our team used a particle accelerator to measure a property known as the miwon’s magnetic moment.
Each muon behaves like a tiny bar magnet when it comes into contact with a magnetic field, an effect known as a magnetic moment. Muons also have an internal property known as a “spin” and the relationship between spin and magnetic moment of “spin”. The muon, called the g-factor, is predicted that the “g” of the electron and the muon will be two, so g minus two (g-2) should be measured to zero. This is what we are testing at Fermilab.
For these tests, the scientists used accelerators, the same technology Cern used with the LHC.The Fermilab accelerators generate mions in very large quantities and measures, very precisely how they interact with the magnetic field.
Read more: Evidence of the newest physics at Cern? Why are we cautiously optimistic about our new findings?
Muon’s behavior is influenced by “virtual particles” that emerge in and out of existence from a vacuum. These things exist for a moment. But long enough to affect how muons interact with the magnetic field and change the measured magnetic moment, even if they are small.
The standard model predicts very precisely what this effect is. As long as we know which particles are foaming in and out of the vacuum, the experiment and theory should match. But if the experiments and theories do not match, our understanding of the virtual particle soup may be incomplete.
The possibilities of existing new particles are not idle speculation. Such particles could help explain many of the big problems in physics. For example, why does the universe contain so much dark matter that galaxies spin faster than we might imagine, and why is almost all the resistance to matter created in the Big Bang?
The problem so far is that no one has seen these proposed new particles, hopefully the Large Hadron Collider (LHC) at Cern will generate them in high-energy proton collisions. But it has not been observed.
The new measurement uses the same techniques as the experiments at Brookhaven National Laboratory in New York earlier in the century that followed a series of measurements at Cern.
Brookhaven’s experiment measured the error against a standard model with a one in 5,000 chance of being a statistical coincidence. This is roughly the same probability as 12 consecutive coin tosses.
This is tantalizing. But the below-threshold approach for discovery, which generally had to be better than one of the 1.7 million or 21 dollars thrown in a row. To determine if new physics is being played, the scientists have to increase the sensitivity of the experiment by a factor of four.
To make better measurements, the magnet at the heart of the 2013 experiment 3,200 miles had to be moved from Long Island along the sea and road to Fermilab just outside Chicago, where accelerators were able to create a vast supply of muons.
Once in place, new experiments have been built around magnets with state-of-the-art detectors and equipment.The muon g-2 experiments began accepting data in 2017 with a collaboration of veteran Brookhaven Experiments and young physicists.
The new results from the first year of data at Fermilab are consistent with Brookhaven experimental measurements. Combining the results underscores the case of incompatibility between the experimental measurement and the standard model. Right now, the chance is roughly one in 40,000 of the error, which is a coincidence. But still embarrassed by the gold standard discovery criteria
Interestingly, recent observations by the LHCb experiment at Cern also found possible deviations from the standard model. The exciting thing is that this also refers to the properties of the miwon. This time, it’s the difference in the production of muons and electrons from heavier particles. Both rates are expected to be the same in the standard model. But from the experimental measurement, it was found that the rates were different.
Taken together, the results of LHCb and Fermilab strengthen the cases where we observe the first evidence of the failed standard model prediction and any new particles or forces in nature to be discovered.
For final confirmation, this requires additional data, both from the Fermilab muon trial and from the Cern LHCb trial. Results will be available in the coming years. Fermilab has four times more data than what is currently used in this latest result. In the process of analysis, Cern has begun to acquire more data and is building a new generation of muon experiments.This is an exciting era for physics.
This article by Themis Bowcock, Professor of Particle Physics, University of Liverpool and Mark Lancaster, Professor of Physics, University of Manchester, is republished from The Conversation under a Creative Commons license. Read the original article