7/28/2014 Peter Durantine

Unlocking an Exotic Atom's Properties in One Millionth of a Second

Inside a physics laboratory at Franklin & Marshall College, senior Matthew Salinger stares at a large blackboard filled with mathematical equations.

"It's wrong somewhere," the double major in math and physics said. "It's all one big calculation and something went wrong somewhere."

In two other labs, physics majors Christian Parsons and Ruihan Wang, both juniors, are pondering similar equations. The three Hackman Scholars are working with an F&M physicist who, with funding from the National Science Foundation (NSF), embarked this summer on a three-year project to study the properties of an exotic atom called positronium. The atom is "a little bound thing" with a short lifespan that, unlike normal atoms, contains equal parts matter and anti-matter, said William G. and Elizabeth R. Simeral Professor of Physics Greg Adkins.

"I've undertaken to calculate its properties," said Adkins, whose breadth of scholarship the last 30 years includes research on positronium as well as quantum field theory and gravity. 

  • Franklin & Marshall College Physics Professor Greg Adkins, with funding from the National Science Foundation, has embarked this summer on a three-year project to study the properties of an exotic atom called positronium. His research assitants are three Hackman Scholars, from right: senior Matthew Salinger, and juniors Christian Parsons (center, next to Adkins) and Ruihan Wang. (Photo by Melissa Hess)

A British theoretical physicist suggested in 1928 that an electron with positive charge (an anti-electron, or “positron”) was likely to exist. In 1951, an American physicist discovered the electron-positron “atom” called “positronium” through instrument readings of radiation decay.

Positronium's properties have been calculated since the 1940s, Adkins said. "What we're doing is working to achieve a higher level of precision in the application of the theory “Quantum Electrodynamics” to the bound system positronium.”

In so doing, Adkins and his student researchers will determine whether the atom is working according to current predictions.

"Possibly, it will show a defect in the theory or, possibly, it will show that the current theory is just fine," Adkins said. "If it turns out there is a defect, who knows where that will go.  It might be an indication of “new physics” such as previously unknown particles or forces or different dimensions of space-time.”

The research involves a series of steps. The first is to figure out how to measure the properties of the atom, which has a life span of a fraction of one millionth of a second. That's done at other labs around the world. The task for Adkins and his team is to provide predictions. This requires making elaborate calculations, such as those challenging the Hackman students, first on paper and blackboard, and then the computer.

  • Franklin & Marshall Physicist Greg Adkins' breadth of scholarship the last 30 years includes research on positronium as well as quantum field theory and gravity. Here, he discusses caluctions with senior Matthew Salinger, a double major in math and physics. (Photo by Melissa Hess) 

"This is a great way to train students," Adkins said. "Besides fueling their scientific interest, they learn how to make contributions."

Since something as minor as a mathematical symbol in the wrong place could make a calculation incorrect, the students are working independently -- and essentially at the graduate level -- on calculations to serve as a check on Adkins' work.

"They're learning a lot about theory and they're becoming very good at how to use it to make these calculation," he said. "It's essential to have this back up."

Adkins meets the students each summer morning to discuss their progress before he settles into his office and they in their labs. The work has reinforced the students' desire to pursue physics as well as re-directed one assistant's interest in the field.

"I came to F&M with no interest in theoretical physics," Parsons said. "This project has definitely changed my opinion on that."

Adkins is collaborating on the project with other physicists around the country. His $180,000 grant provides $60,000 per year over three years.

"I'm grateful I was able to make my case to the foundation,” Adkins said.  “With NSF support we will be able to both advance theoretical understanding and train student researchers.”

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