Lab Canada

Leader of Sudbury Neutrino Observatory wins top Canadian science prize

Ottawa, ON November 24, 2003 Dr Arthur B McDonald was today named winner of the 2003 Gerhard Herzberg Canada Gold Medal for Science and Engineering.

The prize guarantees that Dr McDonald, a professor at Queen’s University, will receive $1 million in research funding from the Natural Sciences and Engineering Research Council (NSERC).

Dr McDonald was born in Sydney, Nova Scotia, on August 29, 1943. He graduated from Dalhousie University in Halifax, Nova Scotia, in 1964 with a BSc (Hon Physics) and 1965 with an MSc (Physics). He continued his studies at the California Institute of Technology in Pasadena, graduating in 1969 with a PhD in Nuclear Physics.

From 1969 until 1981 he worked at the Chalk River Nuclear Laboratories of Atomic Energy of Canada, performing fundamental nuclear physics experiments with particle accelerators. In 1981 he began a professorship in the physics department at Princeton University, Princeton, New Jersey, and continued his research program there as co-principal investigator of the Princeton cyclotron.

In 1989 he moved to Queen’s University in Kingston, Ontario, as professor of physics and director of the Sudbury Neutrino Observatory (SNO) Institute. In 2002 he was awarded a university research chair at Queen’s University.

Dr McDonald’s discoveries about the nature of neutrinos were the result of one of the major physics experiments of the 20th century the massive, underground Sudbury Neutrino Observatory (SNO). SNO is a scientific achievement that involves the uniquely Canadian intersection of heavy water, a mine two kilometres underground, and abundant physics expertise and connections. For Dr McDonald, the initial SNO results were the culmination of over three decades spent considering the intersection of nuclear, particle and astrophysics, and particularly how to measure sub-atomic phenomena at the very limits of detection.

When he was at Caltech in the 1960s, Dr McDonald worked in the lab of Dr William Fowler, who won the Nobel Prize for his work describing the nuclear reactions that power stars. Dr Fowler’s theory, expanded by Dr John Bahcall, quickly raised a conundrum: While experimental tests were largely consistent with his standard solar model, the detection of neutrinos reaching the Earth, first measured by Nobel Laureate Dr Raymond Davis in the mid-1960s, was far too low. This anomaly became known as the solar neutrino problem.

While major experiments tried and failed to resolve the sun’s neutrino riddle, Dr McDonald studied the weak interaction, one of the four fundamental forces (along with the strong force that holds the atomic nucleus intact, gravity and electromagnetism). First at Atomic Energy of Canada’s (AECL) Chalk River Laboratories in the Ottawa Valley and then at Princeton University, Dr McDonald developed sophisticated ways to look for parts-per-million differences in the symmetry of nuclear reactions and the role of the weak force in this.

In 1989, after two years as the project’s US spokesperson, he was recruited as director of the SNO project, initiated in 1984 with Herb Chen of the University of California at Irvine and George Ewan of Queen’s University as co-spokesmen.

In building the SNO, Dr McDonald managed the creation of the most sensitive neutrino detector to date. It was a massive engineering project that involved the construction of an ultra-clean, 10-storey-high neutrino detector, containing 1,000 tons of heavy water (worth $300 million, on loan from AECL), two km underground in INCO’s Creighton nickel mine in Sudbury. SNO would be the first neutrino detector able to detect all three kinds of neutrinos (electron, muon, and tau) and to be able to distinguish electron neutrinos from the others.

He also assembled a diverse and highly skilled collaboration of more than 130 researchers and technicians from more than a dozen universities and labs in Canada, the US and Britain. The group created a detector from materials that had natural radioactivity levels a billion times lower than tap water, designed special-purpose electronics, and then developed detailed computer models of what to expect.

Since November 1999, SNO has been recording the barely perceptible energy signals of solar neutrinos hitting the detector. Once these thousands of neutrino “hits” were sorted from the nearly half-a-billion “events” recorded by the detector (due to other forms of radioactive energy), the SNO team was able to make a remarkable conclusion. The electron neutrinos produced by the sun were morphing into their sister forms during their journey from the core of the sun to earth, a fact that meant they also have mass. The results also convincingly confirmed the accuracy of Drs Fowler and Bahcall’s detailed solar models.

Future funding from the Canada Foundation for Innovation will enable the creation of SNOLAB, a new international underground laboratory near SNO, aimed at further filtering of the cosmos for consistency with the standard model. For that project, one of the targets is WIMPS (weakly interacting massive particles), enigmatic particles predicted by theories that extend beyond the standard model and one of the leading candidates for the 25% of the universe believed to be made from Dark Matter.

"Designing and building a large underground experiment to reveal the ultimate truth about solar neutrinos was both a novel and high risk endeavour," says Tom Brzustowski, president of NSERC. "Yet Art McDonald recognized that Canada had the ingredients to pull it off, and he did. Thanks to his great abilities as a scientist, mentor, leader and coordinator, we have an amazing scientific facility in Sudbury, and Canada is recognized as a major training ground for particle, nuclear and astrophysicists from around the world."

Dr McDonald will receive the Herzberg Medal at a gala dinner Tuesday evening at the National Gallery of Canada. The event will also feature an address by Canadian entrepreneur Mike Lazaridis.