Evidence of new physics MSUToday

Researchers at Michigan State University have helped capture particles called muons by behaving in a way not provided for in the Standard Model of Particle Physics – the best theory scientists have to explain basic space particles and forces.

This deviation suggests that new physics, such as undiscovered particles or forces, should be explored.


The Muon g-2 magnetic ring is located in its detector room in the middle of electronic carriers and other equipment. The experiment runs at a negative 450 degrees Fahrenheit. Photo courtesy of Fermilab.

“The first results of the experiment at the Fermi National Accelerator Laboratory show strong evidence that our understanding of the subatomic world is incomplete,” said Martin Berz, a professor at Department of Physics and Astronomy in MSUs College of Natural Science. Fermilab, located near Chicago, is a laboratory of the U.S. Department of Energy’s Office of Science.

The results of this experiment, which is called The Muon g-2 experiment confirmed the disagreement that has plagued researchers for decades. The team published its milestone in the journal Letters of physical examination April 7.

The stock exchange is part of a team of 190 people, representing 35 institutions from seven countries, exploring fundamental physics with the power of Fermilab particle accelerators. The Spartan contingent of the team worked on precise calculations of the dynamics of the muon orbit beam, which helped the Muon g-2 experiment to achieve incomparable precision with its measurements.

MSU professor Martin Berz

MSU professor Martin Berz

“Cooperation was crucial in this experiment. “Previously unattainable precision could only be achieved through the very close interaction of the skills of many separate world-leading groups with different areas of expertise,” said Berz. “It was great to see how all the years of hard work on this project have borne fruit.”

Other Michigan associates include Kyoko Makino, a professor of physics and astronomy, as well as postdoctoral researcher Eremey Valetov and graduate students Adrian Weisskopf and David Tarazona.

Today is an extraordinary day, which has long been awaited not only by us, but also by the entire international physical community, ”said Graziano Venanzoni, Associatea spokesman for the Muon g-2 experiment and a physicist at the Italian National Institute of Nuclear Physics. “Great credit goes to our young researchers who, with their talent, ideas and enthusiasm, have enabled us to achieve this incredible result.”

A muon is about 200 times more massive than its cousin, the electron. Muons occur naturally when cosmic rays strike the Earth’s atmosphere. Fermilab particle accelerators can also produce particles in large numbers.

Like electrons, muons behave as if they have a tiny inner magnet. In a strong magnetic field, the direction of the muon magnet is preceded or conditioned, similar to the axis of a rotating tip or gyroscope. The strength of an inner magnet determines the rate at which a muon converts in an outer magnetic field and is described by a number that physicists call the g-factor. This number can be calculated with extremely high precision.

The Muon g-2 magnet floats on a rust-colored barge on the Illinois River, moving toward Fermilab.  The outer part of the ring is wrapped with white and red metal spokes that help support its inside.

This 2013 photo shows a ring of a g-2 Muon magnet moving along the Illinois River on its journey to Fermilab. Photo courtesy of Fermilab.

In the Muon g-2 experiment, muons circulate in a large magnetic storage ring. Within this ring, muons also interact with the quantum foam of subatomic particles that pop up and out of existence. Interactions with these short-lived particles affect the value of the g-factor, causing the muon precession to accelerate or slow down very little. The standard model predicts this so-called anomalous magnetic moment extremely accurately. But if the quantum foam contains additional forces or particles that are not covered by the Standard Model, it would further adjust the muon g-factor.

“This amount we are measuring reflects the interaction of muons with everything else in space. But when theorists calculate the same amount, using all the known forces and particles in the Standard Model, we don’t get the same answer, ”said Renee Fatemi, a physicist at the University of Kentucky and subsystem manager for the Muon Experiment g-2. “This is strong evidence that muon is sensitive to something that is not in our best theory.”

A previous experiment in the Department of Energy at Brookhaven National Laboratory, which he concluded in 2001, gave indications that the behavior of the muons did not agree with the Standard Model. The new measurement from the Muon g-2 experiment at Fermilab strongly agrees with the value found in Brookhaven and deviates from the theory with the most accurate measurements to date.

The Fermilab experiment again uses the main component from the Brookhaven experiment, a superconducting magnetic ring to change the diameter of 50 feet. In 2013, it was transported 3,500 miles by land and sea from Long Island to the suburbs of Chicago, where scientists could use Fermilab’s particle accelerator to produce the most intense muon beam in the United States.

“After 20 years that have passed since the end of the Brookhaven experiment, I’m glad we’ve finally solved this mystery,” said Fermilab scientist Chris Polly, who is the interlocutor of the current experiment and was a graduate student of the experiment.

“So far, we have analyzed less than 6% of the data that the experiment will eventually collect. Although these first results tell us that there is an intriguing difference with the Standard Model, we will learn much more in the next few years, ”said Polly.

“What monsters can I lurk there?” he asked at the virtual conference presenting the results.

“Eliminating the subtle behavior of muons is a remarkable achievement that will guide the search for physics beyond the Standard Model for years to come,” said Fermilab, deputy director of research Joe Lykken. “This is an exciting time to explore particle physics, and Fermilab is at the forefront.”

Fermilab is the leading US national laboratory for particle physics research. The U.S. Department of Energy Laboratory, Office of Science, Fermilab is located near Chicago, Illinois, and is operated under contract by Fermi Research Alliance LLC. Visit Fermilab’s website at http://www.fnal.gov and follow us on Twitter @Fermilab.

The DOE Office of Science is the largest supporter of basic physical science research in the United States and is working to address some of the most pressing challenges of our time. For more information visit http://science.energy.gov.

Source