In this new paper in Physical Review Letters, researchers in the SNO+ Collaboration – including Gabriel Orebi Gann (Nuclear Science Division and UC Berkeley Physics Department) and Logan Lebanowski (UC Berkeley Physics and NSD Affiliate) – have reported the first signals in a water-filled Cherenkov neutrino detector from neutrinos emitted by a nuclear reactor. Their work is featured in a recent Physics Magazine article.

The SNO+ detector was inherited from the earlier Sudbury Neutrino Observatory (SNO), located 2 km underground in a mine near Sudbury in Ontario, Canada. After its upgrade in 2018, it was filled with water so that the detector components could be calibrated and its intrinsic radioactive background signal could be characterized.

The team took this opportunity to conduct some additional experiments, using two different analytical methods to distinguish reactor antineutrinos in the water-filled detector. Their results yielded consistent evidence for antineutrinos with a combined 3-sigma signal that matched what would be expected for antineutrinos coming from nuclear reactors at least 240 km away.

“It intrigues us that pure water can be used to measure antineutrinos from reactors and at such large distances,” says Lebanowski, the paper’s lead author. “We spent significant effort to extract a handful of signals from 190 days of data. The result is gratifying.”

The team’s new findings introduce the possibility of using neutrino detectors made from a safer (non-toxic and easier to handle) and less-expensive material to identify the presence of nuclear reactors. The finalized SNO+ detector, which has now been refilled with a complex liquid that lights up when charged particles pass through it, will soon be ready to search for an as-yet-undetected nuclear decay process that would allow researchers to confirm that the neutrino is its own antiparticle.

Learn More

Evidence of Antineutrinos from Distant Reactors Using Pure Water at SNO+
March 1, 2023 / A. Allega et al. (The SNO+ Collaboration) / Physical Review Letters

Reactor Neutrinos Detected by Water
March 1, 2023 / Katherine Wright /Physics Magazine