Behind every baseball, pitched, hit or dropped in the dirt lies the secret of mass, the fundamental property causing the inertia that keeps a sinker ball moving away from the pitcher's mound and the gravity that draws it down over home plate. Where mass comes from is a riddle that Kevin McFarland, assistant professor of physics and astronomy at the University of Rochester, is determined to solve.
McFarland's research has earned him an Outstanding Junior Investigator award from the Department of Energy. This award helps talented young physicists establish research programs early in their careers, and will contribute $400,000 to McFarland's five-year study, starting with $80,000 this year. McFarland will explore why subatomic particles have mass and from whence it comes by studying the top quark---the heaviest of the 12 most basic building blocks of matter.
Currently, McFarland and his team of seven students and postdoctoral researchers, including two graduate students from the University, are participating in preparations for a large-scale experiment at the Department of Energy's Fermi National Accelerator Laboratory near Chicago. The experiment, known as CDF, will use the Tevatron supercollider, one of the world's most powerful accelerators. Approximately 500 physicists and several hundred engineers and technicians are working on CDF, while another large group is preparing for an experiment known as D0. Recent improvements to the laboratory's detectors and accelerator will yield more intense and energetic beams of protons and antiprotons, and more subatomic particles from collisions.
"I think we should see our first proton-antiproton collisions in early 2000 and have usable data---top quarks---from high-intensity collisions by the end of 2000," McFarland says.
In preparation for the experiments, McFarland is leading the construction of a network of hundreds of computers that will analyze data from collisions immediately as they occur. His team is building a "farm" or cluster of 200 to 400 personal computers programmed to make decisions together. "Essentially, we're building a tremendous supercomputer out of equipment you can buy at a computer store," he says. The computers will analyze digitized data sent to them by a detector, a device akin to a very complicated digital camera that records quarks and most other subatomic particles. A system that McFarland created will filter the tremendous amount of data as it pulses through the detector. The computer farm will then analyze and select the most interesting information from the reduced data input.
Accumulating the data from this experiment will take two or three years, at least, McFarland says, and will be used by several hundred scientists researching a variety of physics problems. "The day has passed when we could do this type of physics at a single university. The cost of the resources is too great," he says.
As a result, today's high-energy physics is centered around a few powerful particle accelerators and colliders. The accelerator at Fermilab has a four-mile radius that propels protons---the particles that make up most of matter---and antiprotons, or antimatter, at tremendous speeds. The protons and antiprotons are then ejected into the collider where they smash together, creating even smaller particles, quarks and gluons, which spill into the fray. McFarland's research focuses on what happens when quarks and gluons from a proton collide with their counterparts from an antiproton.
"Usually the collision is a glancing blow," says McFarland. "The ones we're interested in are more like a head-on car wreck." These direct collisions can create and release enough energy to produce a top quark, the short-lived particle observed only a few dozen times so far. The powerful equipment that McFarland and his colleagues will use should produce a few thousand top quarks.
"A top quark decays very quickly," McFarland says. "The typical lifetime of a top quark is less than one trillionth of one trillionth of a second. The reason the quark's lifetime is so short is partly due to the large amount of energy bound up in its enormous mass. A single top quark has the mass of 180 times the mass of a proton. Compared to other fundamental particles, the top quark is enormous. For all that mass to be in one particle is very surprising."
McFarland believes strongly in educating the public about the research conducted at Fermilab, which relies on the Department of Energy for more than 90 percent of its funding. In 1994, during his first year at the facility, McFarland created a program giving high school teachers temporary research appointments so they could share what they learned with their students. The Fermilab Teacher Fellowship continues to support one high school teacher each year.
"We have a real obligation in a field like high-energy physics. Fermilab is a big facility, and when you're asking for that kind of support, you have an obligation to explain what you're doing. Talking to high school teachers and bringing them into the lab to show them what we're doing is one way. I hope that the experience ultimately makes them more excited about what they're teaching," McFarland says.
In a similar vein, McFarland served as a mentor this summer at Fermilab to two high school teachers from the Rochester area as part of the QuarkNet program, a national program that partners high school teachers and scientists. Next year, those two teachers will come to the University, one of 12 QuarkNet centers, to show 10 other high school teachers how to implement physics research projects into their curricula.
In addition to winning the Young Investigator Award, McFarland's research earned him recognition as a Sloan Research Fellow in 1998, the same year he joined Rochester. McFarland earned his doctoral degree in physics from the University of Chicago and his bachelor's degree in mathematics and physics from Brown University.