South Korean foundation awards Kim 2005 Science Prize for basic research at Fermilab

The Ho-Am Foundation of South Korea singled out Young-Kee Kim as the recipient of its 2005 Science Prize for outstanding achievements in basic research. But when she spoke to students during her visit to South Korea in June, Kim, a Professor in Physics and the College, emphasized the collaborative aspects of science.

“I told the students that science is really collective work,” Kim said. “It’s almost like we are a big orchestra. You need every instrument.”

Kim’s “orchestra” consists of more than 800 physicists in the Collider Detector at Fermilab collaboration. The Ho-Am Prize honors her contributions to the understanding of fundamental particles and their interactions. The award follows another honor bestowed upon her by her colleagues: on June 1, 2004, she began serving a two-year term as co-spokesman of the CDF collaboration.

Established in 1990 to honor the late Byung-Chull Lee, founder of Samsung, the prize is presented in five areas annually: science, engineering, medicine, the arts and community service. Each recipient receives a gold medal and approximately $90,000.

“My focus is trying to understand the origin of mass,” Kim said. Mass manifests as weight under the force of gravity. But objects in space would be weightless, so physicists also measure mass by the amount of force it would take to move an object in the absence of any force working against it.

Physicists suspect that mass arises from interactions between the various elementary particles and a theoretical particle called the Higgs boson. Despite years of searching, the Higgs boson remains undiscovered, possibly because the particle accelerators currently in operation lack the power to produce one. The construction of the Large Hadron Collider in Switzerland, scheduled for completion in 2007, may solve that problem.

Meanwhile, Kim and her colleagues look for indirect ways of learning more about the Higgs boson.

“If you look at all the elementary particles, meaning particles that don’t have substructure, they have masses all over the place,” Kim said. An electron has a mass approximately 2,000 times smaller than a proton, while the mass of a top quark is more than 370 times greater than a proton’s.

“If you’re going to understand how particles acquire mass, I think naturally the best place to look will be the particles that have the biggest masses,” she said. So for the last 10 years, Kim has measured—with ever-increasing precision—the two most massive particles, the W boson and the top quark.

The W boson has a mass approximately 80 times greater than that of a proton. The top quark is even more massive, yet, unlike a proton, it cannot be subdivided into smaller units. “That’s an amazing particle,” Kim said.

Measurements of the W boson and the top quark suggest that the Higgs mass might be small enough to be observed in experiments at Fermi National Accelerator Laboratory. “Still the uncertainty on Higgs masses are large,” Kim said. It is entirely possible that the production of a high-mass Higgs boson lies beyond the capabilities of Fermilab’s Tevatron accelerator.

“The probability is not great, but you never know. We should keep trying,” Kim said.

More precise measurements of the W boson and the top quark will make it possible to more accurately predict the mass of the Higgs boson. “We just keep pushing,” she said.

The ultimate goal is to formulate a more complete theory that describes the properties and interactions of subatomic particles. While the dominant theory of particle physics is successful in many ways, it cannot explain why particle masses are what they are.

“We need something better, a more complete theory,” Kim said.