Fermilab’s Muon g-2 experiment has made a groundbreaking discovery, unveiling a new precision measurement of the muon’s magnetic property. This finding could potentially lead to the discovery of undiscovered particles and a breakthrough in the field of physics. The results from the experiment have shown a discrepancy between theory and experiment, indicating the possibility of new physics beyond the Standard Model.
The muon is a fundamental particle that is similar to an electron but much more massive. It possesses a tiny internal magnet that wobbles like the axis of a spinning top in the presence of a magnetic field. The speed of this precession, known as the muon magnetic moment, is typically represented by the letter g. According to the simplest level of theory, g should equal 2.
In the Muon g-2 experiment, an international collaboration of scientists at Fermilab repeatedly sent a beam of muons into a superconducting magnetic storage ring. By measuring how rapidly the muons were precessing and precisely determining the strength of the magnetic field, physicists were able to make a more precise measurement of the muon’s magnetic moment than ever before.
The difference between the measurement and the theoretical value of g-2 can be attributed to the muon’s interactions with particles in a quantum foam that surrounds it. This quantum foam consists of particles that blink in and out of existence and can grab the muon’s “hand,” thus altering its interactions with the magnetic field. The Standard Model incorporates these known particles but leaves room for the existence of undiscovered particles that could contribute to the value of g-2.
If the experimental disagreement with theory persists, it could provide the first laboratory evidence of new physics beyond the Standard Model. Gordan Krnjaic, a theoretical particle physicist at Fermilab, stated that this discovery could potentially be the first time that the Standard Model is broken.
The new measurement, announced on August 10, 2023, is twice as precise as the previous one announced in April 2021. The Muon g-2 collaboration has already surpassed its goal of decreasing one type of uncertainty, known as systematic uncertainty, and is now focusing on reducing the statistical uncertainty by incorporating more data into their analysis.
Peter Winter, co-spokesperson for the Muon g-2 collaboration, described the measurement as an incredible experimental achievement. The collaboration aims to release their final, most precise measurement of the muon magnetic moment in 2025, setting the stage for the ultimate showdown between the Standard Model theory and experiment.
The Muon g-2 experiment, supported by the U.S. Department of Energy and the National Science Foundation, involves close to 200 scientists from 33 institutions in seven countries. The collaboration includes nearly 40 students who have received their doctorates based on their work on the experiment.
This recent discovery at Fermilab’s Muon g-2 experiment is a significant step towards understanding the fundamental nature of the universe and might just uncover new physics beyond our current understanding.