“To be able to remotely monitor nuclear reactors by observing the antineutrinos they produce has long been a goal of researchers aiming to apply neutrino technology to nuclear non-proliferation,” says SNO+ director Mark Chen, Gordon and Patricia Gray Chair professor at Queen’s Department of Physics, Engineering Physics and Astronomy. “In addition to providing a new option for those developing reactor monitoring technology, this result also shows that our detector is functioning very well and makes us excited for the next phase of the experiment.”

The recently published study demonstrates the sensitivity of SNO+ to antineutrinos from distant nuclear generating stations, a feature that will be exploited with the detector filled with liquid scintillator.

“Our plan is to make new and precise measurements of how neutrinos change their type as they propagate, further elucidating the phenomenon discovered in the original SNO experiment,” explains Alex Wright, IPP Research Scientist and also a member of SNO+ and Queen’s Department of Physics, Engineering Physics and Astronomy.

The future of SNO+

Since 2022, SNO+ has been up and running, filled with liquid scintillator. The next rare phenomenon scientists hope to observe is neutrinoless double beta decay, a rare radioactive decay that emits no neutrinos.

Usually, when atomic nuclei undergo fusion in the core of the sun, neutrinos are a byproduct of that reaction. Similarly, in nuclear reactors, antineutrinos are produced in beta decay, that is, the breakdown of a neutron in an atomic nucleus into a proton, an electron, and an antineutrino.

However, in neutrinoless double beta decay – up to this day, a theoretical possibility – two neutrons in an atom’s nucleus change into two protons and two electrons, but no neutrinos or antineutrinos. This can only happen if the double decay creates both particle and antiparticle, which would virtually annihilate each other.

If neutrinoless double beta decay is observed, it will therefore prove that neutrinos are their own antiparticles.

“This would have great implications to our understanding of neutrinos; in particular, how they came to have very small but non-zero masses,” says Dr. Wright. “It might even help us to explain one of the great mysteries of the Universe – how there came to be more matter than antimatter and, hence, how we can exist.”