SCIENCE

Mysterious particles

Shedding light on the fate of the universe

TIM POWIS February 26 1990
SCIENCE

Mysterious particles

Shedding light on the fate of the universe

TIM POWIS February 26 1990

Mysterious particles

SCIENCE

Shedding light on the fate of the universe

The location is an unlikely one for an experiment that could shed light on some of the fundamental mysteries of the universe. More than a mile below the barren landscape outside of the Northern Ontario mining city of Sudbury, a team of 12 workers was scheduled this week to begin hollowing out a 90-foot-deep cavern that will eventually house an acrylic tank designed to hold 200,000 gallons of heavy water (water with an alternate form of hydrogen). The purpose of. thejjffid -million project: to detect and study subatomicparticies known as neutrinos, which originate in the sun and stars. Scientists say that the elusive, invisible particles may be the most abundant kind of matter in the universe and that the SudburyJMeutrino Observatory, due for completion In 1995, could help to solve riddles about the origins and fate of the universe.

Although underground neutrino observatories already exist in the United States, Japan and Italy, scientists say that the Sudbury installation, which will be opgrated by scientists from Canada, the United' States and Britain, will be thè'largësTahd most sensitive detector in the world. Indeed, Jean-Paul Nadreau, an adviser to federal Science Minister William Winegard, said that the Sudbury experiment would put Canadian scientists “at the top notch of what’s going on in particle physics.” Because of that, some scientists have predicted that the project would reverse the so-called brain drain, in which scores of Canadian scientists leave the country each year to work in the United States and overseas. Arthur McDonald, who now is a physics professor at Queen’s University in Kingston, Ont., spent seven years teaching at Princeton University in Princeton, N.J., before returning to Canada to become project director at Sudbury. Said McDonald: “This is a great scientific opportunity.”

According to George Ewan, a Queen’s physicist who is a member of the project team, the idea for the Sudbury observatory had interna-. tional origins. While existing underground observatories use either chemical techniques or ordinary water for detecting neutrinos, Ewan said that the notion of using heayy water to find them came from Herbert Chen, a physicist at the University of California at Irvine, who died in 1987. Recalled Ewan: “He called us up, and we started discussing it. We all got together in Ottawa in the summer of 1984 and began developing a proposal.” Winegard officially announced the project in January after Ottawa agreed to contribute $34.9 million to it.The Ontario.gQvernment will provide $7.6 million, while the U.S. energyjdepartment, which will

collaborate on some of the experiments, agreed to contribute $18.5 million.

The core of the project is the underground tank containing heavy water, which interacts

with neutrinos more efficient-

ly than ordinary water. Atom^ ic Energy of Canada Ltd., a federal Crown corporation that uses heavy water as a moderator and coolant in nuclear reactors, agreed to lend the Sudbury project heavy water worth about $300 million.

For its part, the Sudbury-area nickel-mining giant Inco Ltd. donated the use oftHe ?,20jTL. foot-deep shaft at its Creighton Mine to the observatory, which must be located underground to block interference by natural radiation from the atmosphere. Said

George Ewan: “If we had to buy our own heavy water and build our own mine, the experiment would cost $500 million. We’d never do it.” Once the observatory is completed, teams of scientists from 13 Canadian, U.S. and British universities and government laboratories will wait for emissions of neutrinos from the sun to penetrate the underground chamber. When neutrinos collide with the nuclei of the heavywater atoms, sensitive photomultiplier cells will record the amount of light produced. Physicists said that the Sudbury experiment may help to answer the question of why previous measurements of neutrinos reaching Earth from the sun have indicated the existence of only about one-third as many of the particles as physicists had expected to find. Ewan said that existing laboratories may have been unable to detect all of the neutrinos reaching them. Said Ewan: “That’s really why the scientific community looks to this experiment to solve the problems associated with solar neutrinos.”

Some scientists say that the observatory may be able to detect about 10,000 neutrinos a year—more than 50 times the number recorded by existing detectors. According to Ewan, the observatory may help scientists to answer the question of whether or not neutrinos have mass. Because neutrinos are so numerous, said Ewan, that information could help scientists to determine the contribution that neutrinos make to the total mass of the universe.

Such knowledge, in turn, could help physicists to un1 derstand some fundamental characteristics of the universe, and whether it will continue to expand indefinitely. Ewan also said that a better understanding of neutrinos may enable scientists to contribute to the

_ development of the so-called

Grand Unification Theory: a single concept that would explain all the fundamental forces of nature. Said Ewan: “Understanding neutrinos may be one of the only ways to get an indication of the particle that would unify all the forces.” That prospect is likely to lure scores of scientists to Sudbury during the coming decade, to work in the underground laboratory that will try to fathom the secrets

2 of the universe.

TIM POWIS