Last summer, a team of physicists announced a scientific discovery that caused a big stir about some of the smallest bits of matter in the universe — a find thatcould help explain the structure of matter and whathappened during the Big Bang. A find that almost didn’t happen.

The story begins with the hunt for the infinitesimal. Everything in our world — from the human body to the most distant star in space — is made up of tiny atoms. Split those atoms apart and you’ll find protons, neutrons, and electrons. Peer deeply into protons and neutrons and you’ll find smaller particles called quarks, which scientists discovered in 1964. These quarks represent the fundamental building blocks of matter. Theoretical models suggested that these subatomic particles of matter should exist in pairs, triplets, and, among other configurations, groups of five. Experiments offered clear evidence of the pairs and triplets, but not the five-quark object, dubbed the pentaquark.

Scientists have spent decades on a quest to uncover the pentaquark, but its discovery remained elusive. By 1986, editors of the Review of Particle Physics, the standard dictionary of known objects in the universe, predicted it would take 15 years or more to solve any questions about the existence of the pentaquark; many said the search would never yield the prize. Finally, in 1988, the editors eliminated the pentaquark from the pages of the review entirely.

“The general consensus was that it didn’t exist — though why it didn’t, we didn’t know,” says Ohio University physicist Ken Hicks. “At that point, people stopped looking. Those who proposed experiments on it were told they were crazy.”

A Fortuitous Find

Then, in the late 1990s, Dmitri Diakonov of the St. Petersburg Nuclear Physics Institute in Russia developed a new, more specific theoretical prediction of how scientists could locate the pentaquark — a development Hicks describes as learning where to search for the needle in the proverbial haystack. Diakonov suggested to Takashi Nakano of Osaka University in Japan that he might find evidence of the pentaquark from studies of a particle called the phi meson, a project the Japanese scientist and Hicks had been investigating since 1998. Dubious but with little to lose, the team took a look.

In the summer of 2002, Nakano spotted the signature sign in the expected spot and immediately called Hicks. “He was the first to see the signal, but neither of us really believed it at first,” Hicks recalls.

But was it a fluke? The scientific community wouldn’t accept the result until it could be reproduced elsewhere. After Nakano and Hicks announced the result at the International Conference on the Intersections of Nuclear and Particle Physics in Osaka, Japan, in October 2002, the race was on for other experimental groups to either confirm or deny the existence of the pentaquark. Hicks successfully proposed the project to the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility in Newport News, Virginia, where he led a team that endeavored for seven months to reproduce the result from the Japanese experiment. At times, “I was the only one who thought the Japan project was right,” he says. “(My colleagues) had every right to be skeptical.”

Daniel Carman, an Ohio University physicist who was part of the Jefferson lab analysis, also was skeptical at first. After all, past searches for the pentaquark had failed. In the early stages of their analysis, he and his colleagues found no conclusive evidence. But after several trials, the pentaquark emerged as a telltale spike in the scientists’ data.

“We finally found something that was predicted — though exotic — but it gives us more belief in our models,” says Carman, an assistant professor of physics and astronomy who also studies strange quarks and how matter is produced in the vacuum in a separate but related study at the Jefferson Lab.

When the findings were presented to the scientific community, some physicists were dubious, but excitement grew as more confirmation came from labs in Europe. In July 2003, Nakano and Hicks published the first paper on the pentaquark results in the journal Physical Review Letters. “It’s the first new particle discovery in many years,” says Hicks, a “shot in the arm” to the field of particle physics.

The Meaning Of Quark

The discovery of the pentaquark is to a physicist what a new animal species is to a biologist, Hicks suggests. On a basic scientific level, the pentaquark studies help to clarify the forces at work between quarks in nature and how matter is put together. Understanding more about the basics of matter also could shed light on the beginnings of the universe, such as the forces at work in the Big Bang.

“When you understand something about the fundamental process, that’s scientific progress,” Hicks says. And it’s possible, he adds, that applications for the pentaquark that are unimaginable right now may be uncovered in 50 to 100 years.

“A lot of nuclear technology is now being applied to medicine,” Hicks says. “When nuclear reactions were first investigated and understood, no one had any idea how to apply those to cures for cancer. But that’s now being developed.”

One Question Leads To Another

The pentaquark discovery has generated much buzz in the scientific community and news media. Last summer, the pentaquark discovery made international news headlines and Hicks and Nakano fielded calls from reporters with The New York Times, USA Today, and U.S. News & World Report, among others. In January, Discover magazine ranked it ninth on its listof the top 100 science discoveries of 2003.

“It brings science more to the attention of the everyday person, and makes them realize we’re still doing exciting work in bringing new discoveries,” Hicks says about the media coverage.

But the physicist is more interested in how the pentaquark discovery could boost attention to the field of particle physics among prospective students, scholars, and funding agencies. The initial discoveries that have generated some of the most intriguing advances in technology — from electricity to nuclear medicine — all started in the realm of physics, says Hicks, who is funded by the National Science Foundation.

It may be those young physicists who take science’s understanding of the pentaquark to the next level. Now that the object has been found, the scientists will explore issues such as the make up, properties, and decay of the subatomic particle, Carman says. The Jefferson Lab has allowed Hicks 30 days of “beam time” at the accelerator to further investigate the phenomenon this year.

Though the discovery of the pentaquark has opened up new avenues of research for particle physicists, Hicks maintains that the field should continue to exercise caution in approving experiments that search for such elusive objects. The current process is reasonable and necessary to pursue more mainstream questions in science, he argues.

But the pentaquark project has taught Hicks to follow his intuition when the unexpected does pop up.

“Don’t give up if you believe something is there,” he says. “Go look for it.”

For more information about the pentaquark finding, visit the Web at
http://www.ohiou.edu/infocus/pentaquark/.