Postdoc Picks at the Three-Particle Problem

Andrew Jackura wants to know what we’re made of. Now, as the winner of the 2021 Jefferson Science Associates (JSA) Postdoctoral Prize, he’ll get the chance to find out.

Jackura is a postdoctoral research scientist at Old Dominion University and a scientific user at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility. His research focuses on the strong nuclear force, the fundamental force responsible for keeping all ordinary matter in the universe together, including us. 

“As scientists, we want to understand the world around us. Part of that is understanding what makes us up,” Jackura said. “Most of the matter that we see in the universe is made up by strong nuclear interactions, but we don’t understand them from the basic theories we’ve come up with.”

The basic theory used to describe the strong nuclear force is known as quantum chromodynamics, or QCD. This theory mathematically explains how gluons, the force carrier particles of the strong nuclear force, glue another type of particle called quarks together.

Stuck-together quarks form protons and neutrons, the particles that make up the nucleus of an atom of ordinary matter. QCD also explains how the strong nuclear force binds protons and neutrons together in atomic nuclei.

For all of these examples, theorists must perform calculations from QCD to extrapolate information from the theory about the particles they are studying. However, QCD is a complicated theory, so some cases are more difficult to calculate than others. For instance, while physicists have made progress understanding single particles from QCD, reactions between multiple particles are more difficult to calculate. 

To understand what happens when two particles interact, such as a proton and a neutron, physicists typically turn to an alternative technique called lattice QCD. In lattice QCD, a computer runs a bunch of calculations many times to learn information about the interactions in a nuclear system.

The Three-Body Problem

Lattice QCD has improved understanding of two-particle reactions from QCD, but these interactions are still under investigation. Strong nuclear force interactions among three particles are even more complicated and less known.

“We know the three-body force plays a substantial part in nuclear binding for various nuclei, but we don’t know all the details about it,” Jackura said. “We don’t know what makes it tick.”

The the postdoctoral prize will help fund Jackura’s work studying this—the so-called three-body problem.

“The case for three-body forces is still in its infancy, but my work, with my collaborators, is paving the way for this to become a reality, much like the two-body case,” he said.

While earning his doctorate, Jackura developed a framework to understand three-body forces. Now he’s extending it to more complicated systems. His ultimate goal is to better understand strong nuclear interactions in a relatively simple nucleus with three particle inside, the triton. The triton is made up of one proton and two neutrons. 

“I want to study the triton from lattice QCD using the formalism that I helped develop,” he said. “It’s going to be hard. It’s going to take a few years. But I firmly believe we will get there, and I want to be a part of that.”

Prize-Winning Research

The Jefferson Lab User Organization Board of Directors (JLUO BOD) has awarded the JSA Postdoctoral Prize since 2008. The group represents the scientists who come to Jefferson Lab to conduct research with its unique facilities. The board judges each applicant on their record of accomplishment in physics, proposed use of the research grant, and the likelihood of further accomplishments in the Jefferson Lab research fields. 

“It feels amazing to win this award,” Jackura said. “I feel honored that the reviewers thought the research program I’m pursuing is worthwhile. There’s a long list of people who have won this award that have gone on to do great things.” 

The grant is funded by the JSA Initiatives Fund program, which provides support for programs, initiatives and activities that further the scientific outreach, and promote the science, education and technology missions of Jefferson Lab and benefit the laboratory’s user community. The competition was coordinated by Edward Brash, a professor at Christopher Newport University and the JLUO BOD chair-elect, who formed an external committee of reviewers to assess the submitted projects.

“Once again this year, all of the applicants did an excellent job in identifying compelling projects and in writing competitive proposals. This made the choice quite difficult. I want to thank the selection committee, led by Carlos Munoz, for its careful work, along with JSA for funding the prize,” Brash said. “Andrew Jackura’s proposal is exemplary of the outstanding contributions that postdoctoral associates make toward advancing the Jefferson Lab science mission.”

Jackura will use the prize money to present his progress at virtual conferences, and to update his computer.

“If it could run faster, that’d be great, because these calculations take a while,” he said.

He will also fund a doctoral student at ODU, Md Habib E Islam, aka Digonto, who will help develop and test a code for solving related equations.

Fittingly, the postdoc studying the three-body problem has three college degrees. After completing his first bachelor’s degree in mechanical engineering at Purdue University Northwest, Jackura started working in the nuclear engineering department at DOE’s Argonne National Laboratory. 

“While I was working there, I’d attend the nuclear physics seminars taught by physicists and that’s what I really loved,” Jackura said. He started to read nuclear physics books in the library during his lunch breaks. 

“At that point, I wanted to do nuclear physics and push the boundaries of physics,” he said. So, Jackura went back to Purdue University Northwest and earned a second bachelor’s in physics.

While completing his doctorate degree at Indiana University, Jackura’s advisor, Adam Szczepaniak, got him interested in the three-body problem. It was a natural evolution of his curiosity.

“When I first got into physics, I wanted to understand the interactions that happen in a proton,” he said. “Then I built my way up to two particles, and now three.” 

Jackura continues to work with Szczepaniak, as well as Szczepaniak’s grad student, Sebastian Dawid. He met his current advisor at ODU, Raúl Briceño, after getting involved with the Hadron Spectrum Collaboration at Jefferson Lab. Maury High School Student Connor McCarty also joined the team after meeting Briceño through the Python-4-Physics program at ODU. 

Jackura hopes to continue his research beyond the three-body problem, which is only one aspect of fully understanding QCD. 

“One day, I hope I’m lucky enough to push the four-particle boundaries,” he said.

Further Reading
Postdoc Pushes Backward Physics to Fore
Prized Postdoc Works to Demystify Process Behind Quark Combination
Physicist Takes Cues from Artificial Intelligence

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Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science. 

DOE’s 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, visit https://energy.gov/science.