Science & Technology, UK (Commonwealth Union) – A recent, highly precise assessment of the anomalous magnetic moment of the subatomic muon particle has been carried out at the Fermilab in the United States, in collaboration with researchers from the University College London (UCL). This endeavor highlights a perplexing inconsistency between theoretical predictions and experimental findings regarding the muon’s behavior, pointing towards the potential emergence of novel physics.
The most recent findings, which have been submitted to the journal Physical Review Letters, serve to corroborate earlier evaluations of the muon’s magnetic moment, undertaken by the Muon g-2 collaboration—an international team of researchers engaged in this investigation. Nevertheless, the observed magnitude deviates from the projections established by the Standard Model of particle physics. This disparity instills a sense of optimism that there might exist hitherto undiscovered particles or forces that are influencing the outcomes.
“These new, exciting results further reinforce our team’s previous precise measurements of the muon’s anomalous magnetic moment, reaching unprecedented accuracy in testing the Standard Model and probing deeper into the subatomic world,” explained Dr Rebecca Chislett of UCL Physics & Astronomy, the lead of the building and running of the data acquisition system for the experiment.
Muons, fundamental subatomic particles with a negative charge, bear resemblance to electrons but possess approximately 200 times greater mass. Notably, muons exhibit a magnetic property and exhibit a wobbling motion as they rotate in the presence of a potent magnetic field. This characteristic, termed their magnetic moment, quantifies the strength of their inherent magnets and the extent to which an adjacent magnetic field induces their wobbling, referred to as “precession.”
The representation of the muon’s magnetic moment in relation to its spin is symbolized by the variable “g,” which, as per theoretical expectations, should marginally exceed 2. However, the recently disclosed measurements, in alignment with prior experiments conducted by the research team, reveal a magnetic moment that is stronger by approximately 0.2 parts per million—a seemingly minor yet meaningful variation.
In a bid to scrutinize the magnetic moment of these particles, scientists at the U.S. Department of Energy’s Fermi National Accelerator Laboratory propelled beams of muons into a circular, superconducting magnetic storage ring spanning 15 meters in diameter. As the muons navigate this ring at nearly the speed of light, they engage with other subatomic particles that momentarily emerge and vanish, thereby influencing their rate of precession, as indicated by researchers.
The discrepancy between the anticipated and observed precession rates alludes to the potential existence of an undiscovered particle or force that interacts with muons.
This latest experimental phase constitutes an extension of prior endeavors undertaken by the team over the span of several years. The recent announcement supplements the initial year of data collection released in 2021 with an additional two years of data, thereby quadrupling the amassed data volume. This augmented dataset diminishes the margin of uncertainty in the initial measurement, affirming that it’s not solely a result of statistical fluctuations. The team remains engaged in amalgamating three more years of data to achieve a conclusive and definitive evaluation of the muon’s magnetic moment. The precision of the most recent findings is approximately twice that of the 2021 release, possibly establishing a new benchmark for magnetic moment measurement.
Professor Gavin Hesketh of the UCL Physics & Astronomy), a g-2 lead from UCL, says “This is an important update from an extremely difficult experiment, and the result gives us even more confidence in what we are seeing. Researchers from UCL have been essential in getting us this far, and we now focus on analysing the full dataset.”
The findings are likely to shed a new light in studies related to this area of physics.
