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Physics postdoc wins research grant at Jefferson Lab

  • How do you build a proton?
    How do you build a proton?
    Chris Monahan, a postdoctoral research associate in the physics department at William & Mary, has won a grant to use a new approach to figure out how quarks and gluons work together to assemble protons.
    Jefferson Lab photo

Scientists have long puzzled over how the smallest bits of matter add up to the world around us. Now, Chris Monahan will use the power of a video gaming system to attempt a new method of exploring those bits.

Monahan is the recipient of the 2013 JSA Postdoctoral Research Grant at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, which will provide $11,000 for his research. Monahan is a postdoctoral research associate in the physics department at William & Mary.

He was selected for the grant by the Users Group Board of Directors, the governing body of the group that represents scientists who use Jefferson Lab facilities to conduct nuclear physics research.

"Once again, we received some very strong proposals. The board felt that all of the proposals featured worthy projects," says Sebastian Kuhn, board chairman and a professor of physics and eminent scholar at Old Dominion University. "We chose Chris Monahan's, because it most clearly showed where the research grant would make a difference. Board members also felt that his proposal did a very good job describing exactly what he is planning to do, and he had very strong letters of support."

Monahan's research will use a new approach for calculating how the smallest bits of matter, quarks and gluons, come together to build the ubiquitous proton.

"This project is aimed at developing a new way of comparing numerical data from a computer to experimental data. There are a number of ways of doing this, but none of them are ideal. This won't be ideal, but it takes advantage of some new developments," Monahan explains.

The method uses lattice QCD, an approach that harnesses the power of supercomputers to solve the theory that describes how quarks and gluons build protons, neutrons and other particles in the heart of matter. Lattice QCD helps simplify the problem by breaking up space and time into a grid system that a computer can use to calculate numerically the behavior of quarks and gluons.

"I like to picture it like a chessboard. You can imagine that the quarks could really live anywhere on the chessboard. But a computer can't deal with so many possibilities. So instead, you say they can only appear on the black squares. That way, you've only got a finite number of possibilities to deal with," he says.

To increase the accuracy of the computations, the scientists need to make the squares smaller. However, the problem with this method is that the smaller you make the squares, the longer it takes for the computer to run the calculation. Monahan's method may get around that issue. He plans to use the power of a graphics processing unit, the same type of processor that powers gaming systems, to compute the problem differently.

"Instead of making the black squares smaller, you could make the quarks bigger. And then the black squares look smaller to the quarks, comparatively," he explains.

If the new approach works, Monahan says the method could require less computing power to perform these difficult calculations, saving time and money while also benefiting physicists who compare such calculations to the results they get from experiments probing quarks and gluons.

"Given the great importance of lattice QCD calculations to interpret the future 12 GeV program at the lab, the proposed research is clearly of relevance for the core Jefferson Lab physics program," Kuhn said.

Monahan will use about a third of the grant to assemble a computer for testing the new method, another third to fund a new graduate student over the summer to assist with the programming and the last third to attend an international conference of lattice QCD physicists in hopes of presenting his first results.

"Chris Monahan's lattice QCD work is particularly promising, and we are looking forward to his results and potential positive impact on Jefferson Lab research," said Hugh Montgomery, JSA president and Jefferson Lab director. "It is our youth who will make the scientific discoveries and the technological developments of the future. This grant continues our commitment to providing the next generation of scientists with challenging and rewarding research opportunities."

Monahan completed his undergraduate degree in physics (M.Phys.) at the University of Edinburgh and his Ph.D. at the University of Cambridge. He is currently a postdoctoral research associate at The College of William & Mary.

The JSA Postdoctoral Research Grant has been awarded annually since 2008 by the Users Group Board of Directors. In making the award, the board judged each applicant on his or her record of accomplishment in physics, proposed use of the research grant and the likelihood of further accomplishments in the Jefferson Lab research fields. The research grant is one of the funded projects of the JSA Initiatives Fund program, provided by Jefferson Science Associates to support programs, initiatives, and activities that further the scientific outreach, and promote the science, education and technology missions of Jefferson Lab and benefit the Lab user community.