Fermilab’s Muon g-2 Experiment explores uncharted territory with help from North Central physics faculty and students
Aug 18, 2023
The U.S. Department of Energy’s Fermi National Accelerator Laboratory recently announced the latest measurements from its Muon g-2 experiment, bolstering the initial findings released in April 2021 from the same long running project. Collected over the past two years, the findings “set up a showdown between theory and experiment over 20 years in the making,” according to an official announcement from Batavia, Ill.-based Fermilab.
The Muon g-2 experiment is a collaboration comprised of nearly 200 scientists from 33 institutions in seven countries—among them North Central College. Dr. Paul Bloom, associate professor of physics at North Central College, has been involved in the international collaboration for several years, as has Mandy Kiburg, adjunct professor of physics at North Central College and a staff scientist at Fermilab.
A muon (pronounced “meew-on”) is a subatomic particle with an internal magnet—like an electron but about 200 times as massive. The g-2 experiment measures a property of the muon called the “magnetic moment.” Measurement of g-2 corresponds to the precision of 0.20 parts per million. Though tiny, the results could be huge.
“This could mean many things,” said Bloom, referring to the anomaly that was found in the measurements. “New particles, new forces—we don’t know what we don’t know. But it could be a big deal in terms of our understanding of the fundamental constituents of matter and the forces by which they interact.”
“This measurement is an incredible experimental achievement,” said Peter Winter, a physicist at Argonne National Laboratory and co-spokesperson for the Muon g-2 collaboration. “Getting the systematic uncertainty down to this level is a big deal and is something we didn’t expect to achieve so soon.”
One of the reasons the most recent findings are so exciting is the sheer amount of data that has been collected and analyzed. More data reduces the statistical uncertainty of the findings, and it ultimately requires reduced statistical and systematic uncertainties to improve the precision of the measurement.
“It’s the most precise measurement to date of the magnetic dipole moment of the muon,” said Bloom. “By measuring the anomaly with greater precision, we can compare it with the one predicted by the Standard Model, which accounts for all the particles and forces we know about. If they disagree, something really interesting is going on. There could be some new physics making its presence felt. That would be incredible.”
North Central College students have played a critical role in this effort, having worked with Bloom on several facets of the g-2 experiment dating back to 2017.
According to Bloom, his students have performed a variety of quality control and assurance test modules for the charged particle tracking system, and they have been involved in every step of designing, building and improving a “mapping magnetometer” to measure the magnetic field inside the charged particle tracking system.
Two of Bloom’s students—Tyler Weitzel ’19 and Darryl Watkins ’20—partnered with him as successful co-applicants for a U.S. Department of Energy grant and research stipend for their work on the g-2 experiment.
Bloom views these types of hands-on, real-world opportunities as an essential part of the educational experience at North Central College.
“Involving our physics majors in this kind of research is why I do it,” he said. “It’s not possible to understand science without doing actual science. Classrooms have their purpose, so do instructional labs, but ultimately, it’s in the process of discovery and failure that we see how science actually works.”
The collaboration anticipates releasing their final, most precise measurement of the muon magnetic moment in 2025. Bloom and his students will see it through to the end.