Arthur B. McDonald, a Queen’s University professor who directed a watershed particle experiment deep below ground near Sudbury, has won the Nobel Prize in physics.

Dr. McDonald led the team that in 2001 announced that neutrinos – elusive particles produced in the heart of the sun – can change their identity from one type, or “flavour,” to another while travelling through space. The result proved that neutrinos have a slight mass, a fundamental discovery that has important consequences for how matter behaves and affects the evolution of the cosmos.

“It’s a fantastic choice for the Nobel Prize in Physics. If anything, a little overdue. And a big day for science in Canada,” said Ray Jayawardhana, dean of science at York University and author of the book Neutrino Hunters.

Dr. McDonald shares the prize with Japanese researcher Takaaki Kajita, who led a complementary experiment that discovered neutrinos produced by cosmic rays in Earth’s atmosphere also change flavour.

Speaking with reporters by phone at the Nobel ceremony in Stockholm, Dr. McDonald said winning the prize was a “daunting experience.” He praised his many colleagues who worked on the experiment at the former Sudbury Neutrino Observatory, built at the bottom of a nickel mine more than two kilometres below ground. The site has since been expanded to form SNOLAB, which houses a number of ongoing physics experiments.

Dr. McDonald was born in Sydney, N.S., and earned his PhD in physics from the California Institute of Technology in 1969. He was a researcher at Chalk River Nuclear Laboratories, north of Ottawa, before he left to become a professor at Princeton University in 1982. He returned to Canada in 1989 to take up a professorship at Queen’s, where he began planning the ambitious experiment that would show whether neutrinos, first detected in 1956, have mass.

The Globe and Mail
Published Tuesday, Oct. 06, 2015 6:02AM EDT
Last updated Tuesday, Oct. 06, 2015 9:07AM EDT