More than 2 kilometers underground, in a Canadian laboratory, something extraordinary happened. A nearly imperceptible flash passed through a tank of ultrapure water, marking the first detection of antineutrinos using water. These ghost particles, generated by a nuclear power plant 240 kilometers away, could revolutionize the way we monitor the activity of nuclear reactors. A discovery that combines the simplicity of water with the complexity of quantum physics.
The detector that made history
In the heart of Ontario, the laboratory SNOLAB hosts SNO+, a gigantic spherical detector containing 780 tons of liquid. During the calibration phase in 2018, the detector was filled with ultrapure water. A seemingly insignificant detail that turned out to be crucial for this revolutionary discovery in the field of antineutrinos. The depth of the laboratory is not accidental: More than 2 kilometers of rock act as a natural shield against cosmic rays, allowing researchers to obtain incredibly clean and precise signals. This feature has made it possible to detect a phenomenon that until now seemed impossible to capture with water.
The detector structure is designed to capture the faint Cherenkov light: a bit like the “sonic boom” of particles traveling faster than light in water. A sophisticated system that has demonstrated capabilities far beyond initial expectations.
The Dance of Antineutrinos, “Ghost” Particles
- antineutrinos represent one of the most fascinating mysteries of modern physics. They are the counterparts of particles called neutrinos, but they have unique characteristics that make them particularly difficult to study. Unlike other particle-antiparticle pairs, they do not have an electric charge, making their distinction a real puzzle for physicists.
It is intriguing that pure water can be used to measure antineutrinos from reactors and at such large distances.
the physicist commented Logan Lebanowski ofUniversity of California, Berkeley. This discovery opens up new possibilities for monitoring nuclear power plants using simple and safe materials.
The ultrapure water revolution
SNO+’s success in detecting antineutrinos with pure water represents a significant breakthrough. Water Cherenkov detectors traditionally struggle to detect signals below 3 megaelectronvolts, but SNO+ has managed to push it up to 1,4 megaelectronvolts, with a 50% efficiency in detecting signals at 2,2 megaelectronvolts.
Analysis of data collected in 190 days (condensed in this study) revealed a signal that, with a 99,7% probability, was produced by antineutrinos. This seemingly modest result has revolutionary implications for the future of nuclear monitoring.
Antineutrinos, towards new scientific horizons
The discovery, as I mentioned before, also opens new avenues in the fundamental understanding of physics of particles. One of the great unanswered questions concerns the very nature of neutrinos and antineutrinos: are they the same particle? SNO+ is looking for a very rare type of decay that might provide the answer.
It fascinates me to think that a common material like water could become such a powerful tool in the search for the most elusive particles in the universe. It is a reminder that nature still holds countless surprises, ready to be discovered by those who know where and how to look.
