In 2013, TRIUMF, a Canadian laboratory for nuclear and particle physics that works in partnership with York University and the University of Toronto, announced a new breakthrough in understanding neutrinos – nature’s most elusive particles.
July 7, 2013 – The international Tokai to Kamioka (T2K) collaboration designed an experiment to investigate how neutrinos change from one form to another as they travel. TRIUMF researcher Michael Wilking spoke at the prestigious European Physical Society meeting in Stockholm, Sweden, confirming definitive proof of a new type of neutrino oscillation in which muon neutrinos transform to electron neutrinos. It has been known that neutrinos transform from one kind into another, but this particular transformation had never before been conclusively observed and is a major milestone.
In the T2K experiment, a beam of muon neutrinos is produced in the J-PARC accelerator facility in Tokai, Japan. The neutrino beam is monitored by a nearby detector complex ND280 (much of which was built in Canada) and aimed at the gigantic Super-Kamiokande (SK) underground detector in Kamioka, 295 km away. An analysis of data observed at SK associated with the neutrinos from J-PARC reveals that there are more electron neutrinos (28 events) than would be expected (4.6 events) without this new transformation process. This T2K observation is the first of its kind to explicitly see a unique flavor of neutrinos appear at the detection point from a beam initially consisting of a different type of neutrino.
York University made significant contributions to this historic result, focusing on the study of the rate of neutrino production at the J-PARC facility and the rate of neutrino interactions in the T2K nearby detector complex. In order to measure the oscillation effect precisely, these are important components to this measurement since it is necessary to know how many neutrinos are present before oscillations, and how often they interact, to determine how many have transformed.
“This form of transformation is sensitive to matter-antimatter asymmetry in the universe,” says York University physics Professor Sampa Bhadra. “What can be more exciting than studying a particle that may hold the clue to our very existence?”