A Nobel Prize in Physics for Arthur B. McDonald

[Arthur McDonald ] — *Queen’s Professor Emeritus Dr. Arthur B. McDonald is the co-recipient of the 2015 Nobel Prize in Physics*. Photo by Pi Frisk © Nobel Media 2015.

At an early age, Arthur B. McDonald was already busy trying to figure out the way things work.

“His mother will tell you that at age five, he used to take apart clocks,” says Dr. McDonald’s wife, Janet. “Very early he was intrigued by how things work.”

It’s that interest in the mechanics of the world that eventually led Dr. McDonald, the 2015 co-winner of the Nobel Prize in Physics, to study the universe on a fundamental level, through physics.

“In high school, I was interested in science, not necessarily physics. And I had a math teacher, Bob Chafe, in Sydney, Nova Scotia, who inspired many to pursue math,” says Dr. McDonald. “When I started studying at Dalhousie, I went to study math and science, but it was other teachers, Professors Ernest Guptill and Innes MacKenzie, who inspired me in physics. I also found that I could do it and it was fun.”

The Nobel Prize win recognizes the immense contributions Dr. McDonald has made over his lengthy career, but particularly honours his longtime research and groundbreaking findings into neutrinos – sub-atomic particles considered the basic building blocks of the universe.

The Path to the Nobel Prize

Discover how Queen’s Professor Emeritus Dr. Arthur McDonald, a team of Canadian and international scientists, and SNOLAB unlocked the mysteries of neutrinos, redefined the basic laws of particle physics and won a Nobel Prize in the process.

The Sudbury Neutrino Observatory (SNO)

In 1989, he became director of the Sudbury Neutrino Observatory (SNO), located in the Vale (formerly known as INCO) Creighton mine near Sudbury, succeeding Queen’s Professor George Ewan, the Canadian spokesman for SNO the year prior. Working in the world’s deepest underground laboratory, the SNO team – made up of scientists from several Canadian universities – discovered that neutrinos change from one type, or “flavour,” to another on their journey to Earth from the core of the sun. This finding confirmed that these fundamental particles have a finite mass and that the current models for energy generation in the sun are very accurate.

[copyright The Nobel Foundation; photo by Lovisa Engblom] — © The Nobel Foundation;
Photo by Lovisa Engblom

The Prize

The 2015 Nobel Prize in Physics was awarded jointly to Takaaki Kajita and Arthur B. McDonald “for the discovery of neutrino oscillations, which shows that neutrinos have mass.”

The prize was established in 1901. Dr. McDonald is the fourth Canadian, and first faculty member of Queen’s University, to receive the Nobel Prize in Physics. In December, Dr. McDonald travelled to Sweden to receive the Nobel medal from the Royal Swedish Academy of Sciences.

The medal depicts Alfred Nobel (1833–1896), who left the bulk of his fortune to honour outstanding contributions to humanity.

The inscription on the reverse of the medal for physics, taken from Virgil’s Aeneid, reads: Inventas vitam juvat excoluisse per artes which, loosely translated, says, “And they who bettered life on Earth by their newly found mastery.”

[copyright Nobel Media - Alexander Mahmoud — Michiko and Takaaki Kajita, Carl XVI Gustaf and Queen Silvia of Sweden, Art and Janet McDonald. (Photo by Alexander Mahmoud courtesy of Nobel Media)

Dr. McDonald shares the prestigious Nobel win with Japanese scientist Takaaki Kajita, a professor at the University of Tokyo who similarly found, at the Super Kamiokande detector in Japan, that neutrinos created in the atmosphere underwent a metamorphosis in their journey to Earth.

“I am truly honoured,” says Dr. McDonald. “While I am a co-winner of the Nobel Prize, the honour really represents a culmination of the hard work and contributions of many colleagues with whom I have collaborated during my career.”

The early years on the east coast

Dr. McDonald grew up in the small Nova Scotia city of Sydney, where a tightknit family gave him a strong sense of community and laid the foundation for his successful career.

“There was a lot of knowledge and respect there, within his family,” says Mrs. McDonald, who is also from Sydney and met Dr. McDonald at a dance in high school. The couple will celebrate their 50th wedding anniversary in 2016.

“He’s very clever, but along with that, he has a really good sense about things. He’s multi-faceted,” she says.

“Art has a wonderful way with people. He is very humble and respectful, and I think that’s why the SNO collaboration has done so well. They are all very collegial. That starts with the director and permeates through the group.”

I am truly honoured. While I am a co-winner of the Nobel Prize, the honour really represents a culmination of the hard work and contributions of many colleagues with whom I have collaborated during my career.

Dr. McDonald left Sydney for Dalhousie University in Halifax, graduating in 1964 with a BSc (Honours) in physics and a year later, with an MSc in the same field. From there, he headed south, and west, to complete a PhD in nuclear physics at the California Institute of Technology in Pasadena. He and Mrs. McDonald came back to Canada in 1969 and settled in Deep River, where Dr. McDonald worked at the Chalk River Nuclear Laboratories with Atomic Energy of Canada, performing fundamental nuclear and particle physics experiments with accelerators and reactors.

From Princeton to Queen's

After 12 years in Deep River, Dr. McDonald was offered a position at Princeton University. They were raising their four children in Deep River, and while somewhat reluctant to leave, the family moved and stayed in Princeton until 1988, when Dr. McDonald came to Queen’s on sabbatical for a year and stayed on permanently – a move encouraged by Dr. Ewan as well as Dr. Don Taylor, head of Physics at the time.

“While I was at Chalk River, I was already working with scientists from Queen’s who became the SNO team here,” says Dr. McDonald. “And when I was at Princeton, I returned to Chalk River in the summers to complete research. Our SNO collaboration began in 1984 and I started to study low radioactivity materials in our labs at Princeton.”

As project director at SNO, now known as SNOLAB, Dr. McDonald was responsible for the development, construction, commissioning and operation of the unique underground site, as well as the analysis and presentation of scientific results. It was his persistence, dedication and leadership over many years that paved the way to the significant scientific breakthroughs made by the team.

“We knew that we could make a significant measurement on the property of neutrinos, if we could only complete this very complex project and control radioactivity to an enormous degree,” he says.

At SNO, Dr. McDonald’s leadership led to the creation of the ultimate in a low-radioactivity instrument using 1,000 tonnes of heavy water as the heart of a solar neutrino detector. Whereas previous experiments had primarily observed electron neutrinos, SNO also observed the total flux of all active solar neutrinos and could show decisively whether the electron neutrinos had changed into other types.

The results from the SNO experiment provided clear evidence that the neutrinos from the core of the sun were changing their type, a process arising from neutrinos of finite mass undergoing oscillations. This result, coupled with results for atmospheric neutrinos from Dr. Kajita’s experiment in Japan, requires modifications to the Standard Model of Elementary Particles to include massive neutrinos. SNO results also provided a very accurate confirmation of current models of the sun and its energy-generation processes.

While Dr. McDonald says he’s retired, he still comes into campus regularly and is busy contributing to two experiments at SNOLAB.

It was a feeling of amazement. I am so grateful, for the award, and for all my colleagues and students who have been alongside me throughout my career.

Of course, the Nobel changes things. It’s a distinction he knows will shift his life in exciting ways. At the same time, he feels a responsibility to represent his colleagues, university and country well when in the spotlight that this prize brings. “It was a feeling of amazement,” says Dr. McDonald. “I am so grateful, for the award, and for all my colleagues and students who have been alongside me throughout my career.”

The SNO Men

Before the neutrino detector was ever put into operation, colleagues from Queen’s and other universities spent years on research, excavation, construction, collaboration, negotiation and trouble-shooting at the Sudbury mine site, often while juggling teaching and other duties at their home universities. In January 2016, members of the original SNO Collaboration got together for coffee in the graduate lounge in Stirling Hall.

Dr. Robertson did research in double beta decay that would prove valuable to the SNOproject.
Dr. Evans worked closely with the INCO engineering team.
Dr. George Ewan, co-founder of SNO, was active in data analysis and detector calibration, as well as securing funding for the lab and its research.
Dr. Mak, part of SNO from the start, developed the specifications for the photo multipliers used in the detector.
Dr. Leslie, formerly the principal investigator for the Queen’s Van de Graaff accelerator group, joined the SNO team in 1986.
Dr. Skensved worked on data analysis for SNO: he continues working at SNOLAB, focusing on the SNO+ and DEAP projects.

Breakthrough Prize

Arthur McDonald, representing the Sudbury Neutrino Observatory (SNO) Collaboration, also received the 2016 Breakthrough Prize in Fundamental Physics, which recognizes individuals who have made profound contributions to human knowledge. The partnership received the prize at a ceremony and gala on Nov. 8, 2015 at the NASA Ames Research Centre in Moffett Field, California.

Learn more about Dr. McDonald's research

This article by Wanda Praamsma was previously published in the Queen's Alumni Review 2015 Issue 4 (Fall)

***The SNOlab Institute is operated under a Trust agreement between Queen’s University, University of Alberta, Carleton University, Laurentian University, Université de Montréal and Vale, and includes external and internal membership from both academic and industrial sectors.