Scientists Succeed In Capturing Elusive "Ghost Particles" Escaping Nuclear Reactor

Neutrinos are fundamental particles with a tiny mass and no electric charge. This allows them to move undisturbed through solid objects, such as the whole planet. Every second, 60 billion neutrinos from the Sun go through every square centimeter of us. To capture these so-called "ghost particles", researchers need enormous detectors. A new method for a specific class of neutrinos was able to go in a completely different direction.

Neutrinos produced in space usually have a lot of energy. To study them and their sources, researchers need to capture the rare instance of one of them hitting an atom and producing a flash of light. This is usually done with building-sized tanks of ultra-pure water or by using glaciers. 

A few years ago, researchers demonstrated that neutrinos that are not as energetic can behave slightly differently with matter. This is known as the Coherent Elastic Neutrino-Nucleus Scattering (CEvNS). Basically, the neutrino interacts with the whole nucleus of an atom, causing a minute change in the motion of the nucleus. The team compared it to a ping pong ball changing the speed of a car by bouncing off it. Sure, the effect would be tiny, but as long as you can measure it, you have your detection.

This was the goal of the CONUS+ experiment, with a detector mass of just 3 kilograms, which is wildly different from the cubic kilometer IceCube in Antarctica or HyperKamiokande in Japan. The team needed a lot of neutrinos and for them to be at low energy. A great source was the Leibstadt nuclear power plant (KKL) in Switzerland.

CONUS+ was placed 20.7 meters from the reactor core, receiving 10 trillion neutrinos every centimeter of the detector every second. These were actually antineutrinos, the antimatter equivalent of the neutrino. The team collected data for 119 days between Autumn 2023 and summer 2024 and found 395±106 neutrino signals. This is consistent with the theoretical calculations.

"We have thus successfully confirmed the sensitivity of the CONUS+ experiment and its ability to detect antineutrino scattering from atomic nuclei," co-author Dr Christian Buck from the Max Planck Institute for Nuclear Physics said in a statement.

Neutrinos and antineutrinos and their properties are explained by the standard model of particle physics, the cornerstone theory of the foundation of reality. Yet, we know it is limited to searches looking to find what predictions do not match reality. This detector might give new insights into the nature of neutrinos.

"The techniques and methods used in CONUS+ have excellent potential for fundamental new discoveries," emphasizes Professor Manfred Lindner, initiator of the project and also an author of the study. "The groundbreaking CONUS+ results could therefore mark the starting point for a new field in neutrino research."

A paper describing the findings is published in the journal Nature.