UNC Physicists Played Key Roles in Nobel Prize Project

The Nobel Prize in Physics was awarded to Takaaki Kajita of University of Tokyo, in Kashiwa Japan, and Art McDonald of Queens University in Ontario, Canada. McDonald led a research project that included physicists at the University of North Carolina at Chapel Hill. The prize was announced today (Oct. 6) by the Royal Swedish Academy of Sciences in Stockholm.

McDonald is a Canadian physicist and was director of the Sudbury Neutrino Observatory (SNO). Three members of the department of physics and astronomy in UNC’s College of Arts and Sciences — John Wilkerson, the John R. and Louise S. Parker Distinguished Professor, Associate Professor Reyco Henning and Senior Research Scientist Mark Howe — worked on the SNO experiment before coming to Carolina.

Please see the full UNC press release on the award and the group’s neutrino research here.

Neutrinos are nature’s most enigmatic fundamental particles. They are the most abundant particles in the universe but very rarely interact with matter and are notoriously difficult to detect. The sun, in particular, has been shown to produce copious numbers of neutrinos from nuclear reactions in its core. However, experiments in the 1980’s and 1990’s only detected about a third to one half as many neutrinos from the sun as was expected from solar models. This became knows as the “solar neutrino problem.” One possible explanation was that the solar models were incorrect in calculating the flux of neutrinos. Another, more radical explanation to some, was that the neutrinos were changing into a different kind of neutrino “flavor” as they traveled from the sun’s core to the earth. Experiments at the time were sensitive to only one type of flavor, which would explain why some of the neutrinos went “missing” if they changed flavor. The Sudbury Neutrino Observatory (SNO) was designed and built to address this issue by measuring the fluxes of all the different neutrino flavors. SNO was constructed underground in the Creighton Mine near Sudbury, ON and started data-taking in 1999. In 2001 it presented the first clear evidence that the solar models were correct and that it was the neutrinos that changed flavor as they propagated through space. This required a significant modification to the established standard model of particle physics. It also showed that neutrinos have mass and opened a whole new field of neutrino physics that, among other topics, is trying to understand the nature of matter in the universe at its most fundamental level.

Wilkerson, Howe and Henning are now working on the next big question about neutrinos, which is whether they are their own antiparticles. UNC-Chapel Hill is the lead institution for a major international experiment, called MAJORANA, that will attempt to address this question. Wilkerson also is the inaugural director of the new Institute for Cosmology and Astrophysics, Subatomic Matter, and Symmetries (CoSMS Institute), a joint physics institute headquartered at UNC-Chapel Hill and organized to work on fundamental problems at the leading edge of basic physics research. CoSMS is a partnership with Duke, NC State and Oak Ridge National Laboratory.

Further reading:
UNC’s Experimental Nuclear and Astroparticle Physics Group