University of Rochester physicist Edward H. Thorndike has won the American Physical Society's 1999 W.K.H. Panofsky Prize in Experimental Particle Physics for research that has played a pivotal role in shaping our current understanding of how a few tiny particles known as quarks and leptons combine to form everything in the universe. This award recognizes Thorndike's nearly 20-year study of the "b" or "bottom" quark, one of 12 basic particles that make up every object in the universe.
Considered to be a leading expert on the b quark, Thorndike established how the particle is made and how it transforms itself into lighter quarks. He conducts much of his research at the Cornell Electron-positron Storage Ring (CESR), a particle accelerator built 60 feet beneath a soccer field at Cornell University that is known among scientists as a "B Factory" for its proficiency at producing the exotic particles. There Thorndike heads the CLEO collaboration, a group of 200 physicists who use the facility.
To observe as many b quarks as possible, the physicists use an electron synchrotron to accelerate lightweight electrons and positrons, the positively charged anti-matter equivalents of electrons, to nearly the speed of light before injecting them into the storage ring. The two streams of particles pass through each other more than a million times per second. Eventually an electron and a positron crash into each other, creating a burst of energy that gives rise to much heavier particles containing b quarks. Sensitive particle detectors record the paths and energy of the particles, and sophisticated computer software helps physicists analyze the results.
Observation of the b quark's decay initially eluded scientists following its discovery in 1977, because the b quark and its "shadow" particle, the anti-b quark, would annihilate each other before the b quark could transform into something else. In 1980, Thorndike's team earned its first look ever at the process by producing b and anti-b quarks with enough energy to escape from each other.
Thorndike is best known for his work on a process known as "penguin decay," where the b quark decays to the lighter "s" or "strange" quark and a photon. According to Thorndike, the curiously named diagram, in use since the late 1970s, resulted from a dart game in Europe in which the loser had to incorporate the word "penguin" in the title of a research paper. Others say the diagram illustrating the process could conceivably resemble a penguin if one connects the dots and squints one's eyes. Scientists believe penguin decay has the potential to reveal new insights beyond the Standard Model, the term scientists use to describe their current understanding of the particles that compose the universe.
Thorndike has been intrigued by the smallest forms of matter since his days as a graduate student at Harvard University. "Curiosity drives me to ask questions about the b quarks," says Thorndike. "What are they there for? How do they behave? It's impossible to know where the answers will lead; that's what makes it so interesting. Particle physics is a lot like mountain climbing. It's the pursuit or challenge of it that draws you in. You'll find that a disproportionate number of physicists hike or climb mountains."
Thorndike joined the University in 1961 and promptly established his own research program. In 1969, Thorndike won a National Science Foundation senior postdoctoral fellowship, enabling him to study at the European Center for Nuclear Research (CERN) in Geneva, Switzerland. He took a break from b quarks in 1987 to study at an electron storage ring in Japan during a year-long Guggenheim fellowship.
The APS Division of Particles and Fields will present Thorndike with a certificate and gift of $5,000 at its centennial meeting in March in Atlanta. The annual award, one of the highest given to an experimental physicist, was established in 1985 in honor of W.K.H. Panofsky, a former director of the Stanford Linear Accelerator Center at Stanford University.
Recognition from APS came as a surprise to Thorndike, who learned that he had won the prize while answering his e-mail one Saturday morning. Suspecting a prank, he skeptically read the message requesting the topic of his acceptance speech and remained unconvinced until the official letter of notification arrived in the mail the following Monday.