Some people like slamming things together, whether it’s a young child sitting on a floor crashing two matchbox cars into each other or an adult behind the wheel of a bumper car at a fairground.
Gene Van Buren gets to do the same thing, although he’s not using cars. He’s propelling a gold nucleus along a 2.4-mile track at speeds approaching that of light and slamming it into another gold nucleus.
The effects of the collision are more spectacular, albeit on a miniature scale, than watching the bumper pop off a matchbox car. The temperatures in these crashes climb to 4 trillion degrees Celsius. That’s 250,000 times hotter than the temperature in the center of the sun.
“The day when we get to see what [such a collision] looks like on a computer screen, we are all like a bunch of kids,” said Van Buren, an experimental nuclear physicist at Brookhaven National Lab. “It’s so cool. It’s what we’ve been working for for the past decade to do. We remember how exciting this is.”
Besides doing it because they can, nuclear physicists like Van Buren who work at the Relativistic Heavy Ion Collider (RHIC) study the results of those nuclear mash ups to gain a better understanding of the way nature works at very small scales.
When they’ve jammed these tiny particles together, they’ve been able to examine the way smaller ones, like quarks and gluons, interact. Quarks are the building blocks for protons (matter with a positive charge) and neutrons (those with a neutral charge). Gluons, which don’t have mass, serve as the “glue” that holds quarks together.
“From a theoretical calculation, we expected that once you got these gluons and quarks really hot, they wouldn’t want to interact with each other,” he said. Their collisions, however, showed the opposite, that these subatomic particles “still want to stick to each other.”
What that means is that the parts of the nucleus of an atom behave much more like a liquid than a gas. In a gas like air, Van Buren explained, molecules tend to flow freely away from each other. Liquids like water, on the other hand, tend to bind together. That is why water forms droplets when it is spilled.
“For us, this is very exciting because it has implications for the nature” of how these particles behave, “under normal, everyday conditions that we don’t necessarily observe from our perspective of everyday life,” Van Buren said.
At the same time, these experiments may simulate the kinds of conditions that existed during the beginning of the universe, at least according to the big bang theory. At RHIC, colliding these nuclei at such high speeds is similar to making a “little bang.”
The biggest difference, however, is that RHIC doesn’t collide matter with as much “stuff.”
“In the big bang, the universe started out dense and hot with a lot of material and energy. In our case, we have two out of those three” conditions, Van Buren said. “We have the density and heat.”
Still, by examining high temperatures and density, the scientists at RHIC may be able to see “how the universe evolved during that particular epoch.”
Van Buren said down the road, maybe decades of even a hundred years from now, other scientists can use the knowledge he and others are generating at RHIC to engineer new products.
“It was like that with electricity,” he said. “The first people studying it had no idea how this would affect their everyday life. Over 100 years later, look what electricity does. We can learn to engineer things with the knowledge we gain about the universe.”
Physicists like Van Buren are inspired by the first dozen years that RHIC has been operating (its first experiment was in the summer of 2000).
The scientists “have the pioneering spirit of climbing to the top of Mount Everest,” offered Jim Thomas, a visiting physicist from Lawrence Berkeley Lab in California who has worked closely with Van Buren for several years.
In addition to designing collision experiments, Van Buren has helped create computer programs that analyze the results of the collisions.
Van Buren “understands a lot about computers and a ton about physics,” said Thomas. “He’s able to make the physics/ computer connection very nicely.”
If Van Buren ever needs to consult with a computer-programming expert, he doesn’t have to look far. His wife Marie Van Buren, whom he met when he was at graduate school at the Massachusetts Institute of Technology, is a computer programmer at BNL.
The couple met when they joined a volleyball league at MIT. Marie, who is around 5 feet tall, sometimes sets up her 5-foot-10-inch nuclear physicist husband to spike the ball when they are on the same team.
Sports have always been an important part of Van Buren’s life, whether it was soccer in high school, track and racquetball in college or volleyball and, in summer, ultimate frisbee.
Residents of Middle Island, the Van Burens have lived on Long Island since 1998, when Gene did his post-doctoral work for UCLA at Brookhaven National Lab.
As for his research, Van Buren said his primary goal is “pure research,” in which the end result is knowledge, not a product. The basic knowledge of nuclear physics may one day pave “the way for new developments that perhaps no one today can dream.”