Fermilab Physicist Studying Quirky Behavior of Muons Receives Brookhaven's Leona Woods Lectureship Award

Tammy Walton will give two talks at Brookhaven Lab to describe her work on the new Muon g-2 experiment now operating at Fermilab

Tammy Walton enlarge

Fermilab physicist Tammy Walton in front of the Muon g-2 storage ring at Fermi National Accelerator Laboratory. Credit: Fermilab.

UPTON, NY—Tammy Walton, a Research Associate at the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory (Fermilab), has been named the second recipient of the Leona Woods Distinguished Postdoctoral Lectureship Award, given by the Physics Department at DOE’s Brookhaven National Laboratory. Walton is working on the “Muon g-2” experiment now underway at Fermilab following a cross-country journey of the experiment’s giant electromagnet from Brookhaven in 2013. The new experiment is conducting precision measurements to follow up on results reported in the early 2000s by Brookhaven’s version of the experiment. Those measurements suggested that muons, heavy cousins of electrons, were interacting with a powerful magnetic field in a subtly different way than expected, potentially pointing to “new physics” inexplicable by today’s reigning theory of particle physics.

“Physicists are always intrigued by experimental measurements that cannot be explained by ‘the Standard Model’ of particle physics,” Walton said. “Discovering a large deviation between the g-2 experiment’s measurement and the theoretical prediction of the muon’s ‘anomalous magnetic moment’—the property we measure—would be proof of physics beyond the Standard Model.” Such a discovery could point the way to the discovery of a new particle or interaction.

As recipient of the Leona Woods Lectureship Award, Walton will receive a prize of $1,000 and the opportunity to give a general-interest colloquium and a technical talk about her work during a weeklong stay at Brookhaven. She will also participate in informal discussions with Brookhaven physicists, including some who worked on the earlier version of the Muon g-2 experiment and theorists who are continually improving the precision of their predictions for g-2.

“I am honored to receive an award that is named after someone leading the development of nuclear physics, and unknowingly was a pioneer for women in physics. I have never visited Brookhaven, so I’m excited about seeing the lab,” Walton said.

“I also think this award shows that the community is excited about the Muon g-2 experiment at Fermilab,” she added. While at Brookhaven, Walton may get a chance to soak up some of the experiment’s history. “I’d like to see the hall where the Muon g-2 storage ring lived, before it was transported to Fermilab,” she said.

Brookhaven’s Physics Department established the Leona Woods Distinguished Postdoctoral Lectureship Award to celebrate the scientific accomplishments of outstanding female physicists, physicists from under-represented minority groups, and LGBTQ physicists—and to promote diversity and inclusion in the department. It is named for Leona Woods, one of a small number of female physicists who contributed to the Manhattan Project, who later served as a visiting physicist at Brookhaven Lab from 1958 to 1962. During her time at Brookhaven, Woods helped design a muon beam at the Alternating Gradient Synchrotron (AGS).

Muons produced by the AGS were essential to Brookhaven’s g-2 experiment. In the late 1990s and early 2000s, these muons, whose spins were lined up with the direction of their motion, were fed into a powerful circular electromagnet storage ring. As the muons went round and round, their own internal spins and magnetism interacted with the storage ring’s magnetic field, as well as other virtual particles known to pop in and out of existence according to the rules of the Standard Model. If the Standard Model is right, these interactions should cause the spinning muons to precess, or “wobble” away from its spin-aligned path. Sensors surrounding the magnet can measure the muons’ precession with extreme precision.

These Brookhaven measurements indicated that the muons wobbled a tiny bit more than the prediction calculated from what physicists know about the Standard Model. This difference between the experiment’s measurement and the theory’s prediction—which was confirmed with repeated experimental runs and improvements in the precision of the calculations—suggested there was something else going on that the Standard Model could not explain. It was a hint that some yet-to-be discovered particle might be interacting with the muons—“new physics”—but the result was not quite strong enough to declare a discovery. There might be other explanations for the anomalous result, including that there was possibly something wrong with the experiment.

I think this award shows that the community is excited about the Muon g-2 experiment at Fermilab.

— Tammy Walton

That’s why Fermilab wants to repeat the experiment at even higher precision. Fermilab’s muon beam is much more intense and stable than the one used at Brookhaven, so it should reduce the uncertainties in the measurement. After transporting the storage ring across the country in 2013, physicists at Fermilab tuned up its properties, and are now collecting data with an experiment that’s more sensitive to virtual or hidden particles and forces than any previous experiment of its kind. 

Tammy Walton, who witnessed the assembly of the magnetic storage ring at Fermilab, is eager to see the results.

“I write computing software programs used to analyze the data recorded from the Muon g-2 experiment. My primary goal is to produce a measurement and evaluate the uncertainties associated with it,” she said. Ideally, those uncertainties will be low enough to reveal whether the anomalous wobble still stands, and potentially point the way to new discoveries.

Walton will give two talks about her work and the Muon g-2 experiment:

  • A colloquium accessible to non-scientists: May 1, 2018, at 3:30 p.m. in the Large Seminar Room of the Physics Building (510). In this talk, Walton will describe the scientific motivation and physics of Muon g – 2 experiments and conclude with a snapshot of data results from the beginning of the physics run. Add to calendar.
  • A more-technical seminar for scientists: May 3, 2018, at 3 p.m. in the Small Seminar Room of the Physics Building (510). This talk will focus on measuring the spatial distribution and dynamics of the muon beam using advanced tracking detectors and other systems to control various sources of uncertainties in the experiment. Add to calendar. 

Tammy Walton majored in physics at the University of Tennessee, earning her B.S. in 2006. Beginning in 2008, as a graduate student at Hampton University, she conducted research on the MINERvA Experiment at Fermilab, and joined the staff as a Research Associate on the Muon g-2 experiment after earning her Ph.D. in 2014.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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