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BU physicists celebrate historic discovery

Top quark anniversary sparks conference at Fermilab

BU physicists, from left, Ulrich Heintz, Meenakshi Narain and John Butler. Photo by Byron Smith (CGS'08)

The world of particle physics was changed forever 10 years ago at the Department of Energy’s Fermilab in Batavia, Ill., with the discovery of the top quark, and three BU professors were there.

“It was a once-in-a-lifetime experience. Physicists had been looking for the top quark for well over a decade,” says Ulrich Heintz, a College of Arts and Sciences associate professor of physics, who developed one of the techniques used to determine the mass of the top quark.

The top quark is a massive elementary particle that can be produced only in high-energy particle collisions. At 360,000 times larger than an electron, it’s the heaviest known elementary particle and exists for a fraction of a second — specifically a millionth of a billionth of a billionth of a second.

Today at Fermilab (the Fermi National Accelerator Lab) physicists are studying the top quark to understand where the masses of elementary particles come from. Soon, similar work will be done at CERN, the European Organization for Nuclear Research in Switzerland.

In 1995, Heintz, John Butler, a CAS professor of physics, and Meenakshi Narain, a CAS associate professor of physics, were working at Fermilab as part of the team that carried out the discovery work. Butler coordinated the operation of the experiment, worked on the discovery paper, and was part of the group of scientists who built and operated the instruments. Narain was the leader of a group that looked for a particular decay signature of the top quark.

“Our collaboration had been operating the experiment for about three years looking for the top quark,” Heintz says. “In 1995 we had finally accumulated enough data to be able to separate the top quark from background. It all happened very quickly then.

“In January 1995, it became apparent that we might be seeing a signal. We feverishly started analyzing the data, and by mid-February the result was there — we definitely had a signal.” The discovery was announced formally on March 2, 1995. The biggest surprise was the mass of the particle. “It was so large — about the same as the mass of a gold atom,” says Heintz.

Butler came to BU in the fall of 1995; Narain and Heintz followed in 1998. Fermilab is celebrating their discovery today, October 21, with a symposium, Top Turns Ten: Celebrating the Discovery of the Top Quark.

“This was the sort of experience that keeps us going,” Heintz says, “through the years of building detectors and working late-night shifts to record data: that we’ll find something that shapes which direction the future of science takes.”

In other physics news, BU is hosting a two-day Festschrift and conference, The Golden Age of Particle Physics and Its Legacy, today and tomorrow, October 21 and 22, in honor of Lawrence Sulak, BU’s David M. Myers Distinguished Professor, who is also chairman of the physics department. The attendees are expected to include 14 Nobel laureates. To see the agenda, click here.