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New experimental results show a difference in the way neutrinos and antineutrinos behave - which could help us understand why there is so much matter in the universe, but very little antimatter.

The results, released recently from a study of neutrino oscillation, suggest there could be a difference, or asymmetry, between the behaviour of matter and antimatter.

Neutrinos are fundamental particles that make up our Universe and are among the least understood. Yet every second around 50 trillion neutrinos from the Sun pass through your body.

Understanding whether neutrinos and antineutrinos behave differently is important, because if all types of matter and antimatter behave the same way, they should have completely wiped each other out shortly after the Big Bang.

To explore the changes in neutrinos, known as oscillations, the T2K experiment fires a beam, which can switch from neutrinos to antineutrinos, from the J-PARC laboratory on the eastern coast of Japan. When the beam reaches the Super-Kamiokande detector, 295km away, scientists then look for a difference in the oscillations of neutrinos and anti-neutrinos.

The results indicate a high rate of electron neutrino appearances compared to electron antineutrinos – higher than first expected.

This international science experiment is part-funded by the Science and Technology Facilities Council (STFC).

Dr Morgan Wascko, international co-spokesperson for the T2K experiment from the Department of Physics at Imperial, said: “The current T2K result shows a fascinating hint that there's an asymmetry between the behaviour of neutrinos and antineutrinos, in other words an asymmetry between the behaviour of matter and antimatter.

“We now need to collect more data to enhance the significance of our observed asymmetry.”

Although this work is promising, there are still systematic uncertainties, so the T2K team is designing an upgrade to the detector to enhance its sensitivities.

Professor David Wark, Director of Particle Physics at the STFC Rutherford Appleton Laboratory, Professor in Experimental Particle Physics at Oxford University and former spokesperson for the experiment said: “These results confirm the high rate of electron neutrino appearance seen in the earlier data, which is exciting. 

“More running and further experiments will be needed to confirm if this has the exciting explanation that neutrinos and anti-neutrinos don’t oscillate the same way, which could be a clue to why there is so much matter in the universe. 

“Or the explanation could be a more mundane difference, we don’t know yet, but this certainly gives us a strong incentive to continue the search.”

Scientists at the STFC’s Rutherford Appleton and Daresbury Laboratories were heavily involved in collaborating with UK university scientists on designing, building and operating key parts of the T2K detectors and the neutrino beam.

Notes to editors

T2K (Tokai-to-Kamioka) – an international experiment led by Japan and part funded by the UK’s Science and Technology Facilities Council (STFC) - will probe the strange properties of the enigmatic neutrino to unprecedented precision, by firing the most intense neutrino beam ever designed from the east coast of Japan, all the way under the country, to a detector near Japan’s west coast.

T2K involves an international team of around 500 physicists from 63 institutes in 11 countries including the UK, Japan, the US, Canada, France, and Switzerland. The UK T2K collaboration consists of scientists from Imperial College London (including the current International Co-Spokesperson Dr. Morgan Wascko), Lancaster University, the University of Liverpool, Oxford University, Sheffield University, Warwick University, Queen Mary University of London, and the STFC’s Rutherford Appleton and Daresbury Laboratories.