Persis Drell, professor of physics at Cornell University and a noted experimental high-energy physicist, has been named leader of the Cornell group at CLEO -- one of the world's most advanced particle detectors.

With 42 researchers and staff, the Cornell group is the largest in the CLEO collaboration, which embraces 200 members from 22 institutions across the United States, from Harvard to the California Institute of Technology. Housed in Wilson Laboratory on the Cornell campus, CLEO is a magnetic detector apparatus used to study elementary particles produced by the Cornell Electron Storage Ring (CESR), a half-mile-circumference electron-positron collider.

The data that emerge from CLEO are shared among all collaborators, and each team uses the data for independent analysis. However, all research results are published over the names of the entire collaboration.

CLEO is able to make some of the most sensitive tests of the so-called Standard Model describing the elementary particles and their reactions, which is key to understanding the origin and evolution of the universe. In the debris of the collisions of electrons and their anti-particles called positrons are clues as to why the universe started with equal amounts of matter and anti-matter but has evolved into the matter-dominated world we know today.

Drell obtained her doctorate in physics at the University of California at Berkeley in 1983 and was a postdoctoral research associate at Lawrence Berkeley Laboratory from 1983 to 1988. She joined the Cornell faculty as an assistant professor of physics in 1988 and was named a full professor in 1997.

Drell's immediate task is to complete and commission the $15 million upgrade to the CLEO detector, known as CLEO III, that was started in 1994 and will be finished this year. In all, 20 universities have pooled their efforts to create CLEO III over the past five years. "We are struggling to get the new detector to work and to work well," says Drell. "This will be a major focus of our effort for the next year."

It is hoped that by this summer, all of the detector systems will be ready and reading out, and all the data-handling software will be in place.

Accompanying this improvement is the upgrade of the CESR accelerator itself that will allow it to deliver data at a higher rate to the detector. Together, the two upgrades will greatly increase the sensitivity of physics studies at Wilson Lab. In particular, particles such as the b meson and the tau lepton will be measured with precisions never before attainable.

The Cornell group is involved in several projects to analyze and understand these data. Drell's particular interest is in the electroweak interactions of quarks (electroweak refers to the now-accepted theory that the weak force, responsible for some forms of radioactivity, and the electromagnetic force, responsible for electricity, are one and the same). Quarks, as the smallest known building blocks of the nucleus of the atom, cannot exist by themselves, but instead join with other quarks -- through a force known as the strong interaction -- to make mesons. Thus by studying b mesons the hope is to measure the electroweak interactions of the b quarks inside.

The Cornell group has been focusing on two areas of physics that Drell considers the most important to emerge from CLEO. One is looking for extremely rare decays of the b meson, or what Drell calls "looking for the needle in the haystack of enormous data samples." The other is carrying out precision measurements of b meson decays "by which we can access the fundamental parameters that describe the electroweak interactions."

Some studies of the electroweak force require energies much higher than can be created with CESR. However, properties of this force are observable in extremely rare decays of particles composed of b quarks, which provide a "sneak preview" of how the electroweak interaction behaves at much higher energies. Drell notes that the CLEO collaboration, using data obtained before the detector upgrade, already has "the world's best measurements" of these rare decay processes. In addition, CLEO researchers, she says, will soon have new precision measurements of several of the parameters that are necessary for understanding the electroweak interaction of quarks. It is hoped these results will be published this summer.

"If we want to understand the predominance of matter over antimatter in the universe, these are some of the measurements that must be understood," says Drell.