Tech profs help change face of physics - dtucker

Four Louisiana Tech professors just helped rewrite the book on physics. They assisted in proving that “strange” quarks do indeed influence proton structure.

Dr. Neven Simicevic, an associate professor of physics at Tech, in the mid-’90s worked directly with Dr. Doug Beck, spokesman for the G-Zero collaboration and a professor of physics at the University of Illinois at Urbana-Champaign.

There are six types of quarks: up, down, charm, strange, top and bottom. The lightest quarks, called up and down, are the most common. Image: JLab

When Simicevic came to Tech in 1997, he had already contributed to the G-Zero project by designing the particle-detector system and devising computer simulations of the experiment.

Over time, the project was joined by Tech physics professors Dr. Steven Wells, Dr. Kathleen Johnston and Dr. Tony Forest. Later more institutions joined, but Tech was one of the very first.

“The first few meetings, we had maybe 10 people. Now there are around a hundred,” Simicevic said. The research, which involved an international group of 108 physicists from 19 institutions, was conducted at the Department of Energy's Jefferson Lab in Newport News, Va.

Part of the G-Zero detector is shown during the building stage. Image: JLab

“What we learned is that the picture in the standard physics books that students learn from is not fully developed,” Simicevic said. “We have extended this picture because we understand better now how the proton is made.”

Protons are found in what is considered the heart of all matter: the nucleus of the atom. Physicists have long known that protons are primarily built of particles called quarks, along with particles called gluons that bind the quarks together.

Three permanent quarks in the proton are classified as either “up” or “down.” Up and down quarks are the lightest of the possible six “flavors” of quarks.

In addition to the three resident quarks, others appear from time to time but vanish in a tiny fraction of a second. Nuclear physicists, determined to catch some of these ghostly particles in the act of coming and going, chose to look for the next-lightest quark, the “strange” quark, since it seemed the most likely to have a visible effect.

This simplified depiction shows a pair of “strange” quarks in the proton. Nuclear physicists have found that strange quarks, though present for just tiny fractions of a second at a time, also contribute to the proton's properties. Image: JLab

G-Zero equipment worth $10 million allowed researchers to do just that.

“This is like in astronomy when someone discovers a new star or planet,” Simicevic said. “If you discover a new planet, there is perhaps no practical application for that, but discoveries like that feed our curiosity and help us better understand the world around us. And like with almost any discovery, you don’t know what all may come of it.”

G-Zero is a multiyear experiment financed by the U.S. Department of Energy and the National Science Foundation. In addition, contributions of hardware and manpower were also made by Centre National de la Recherche Scientifique in France, and Natural Sciences and Engineering Research Council in Canada.

Simicevic said that when he and Wells came to Tech in 1997 (he from the University of Illinois at Urbana-Champaign and Wells from MIT), the Jefferson Lab, home of the G-Zero project, supported their research for several years by paying half their salaries.

He also credited yearly NSF grants that not only supported his and Wells’ research but also Johnston’s and Forest’s contributions to the project.

Next, Simicevic and Wells will work on a project of theirs called “N to Delta” which will be conducted using the same $10 million apparatus that the G-Zero project used.

“This experiment is similar to G-Zero and will further extend our knowledge of the proton,” Simicevic said.