Global neutrino study brings scientists closer to solving the universe’s biggest mystery of existence

Inside Japan’s Super-Kamiokande neutrino detector. (Image: Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo)

Could the answer to why our universe exists lie within ghostlike particles that rarely interact with matter? A global team of scientists believes they are closer to finding out.

T2K and NOvA Combine Forces Across Continents
For the first time, researchers from Japan’s T2K experiment and the United States’ NOvA experiment have merged their data to study how neutrinos change type as they travel. Their findings, published in Nature, mark a major step towards understanding why matter triumphed over antimatter after the Big Bang.

The joint analysis, co-led by Michigan State University (MSU) physicist Kendall Mahn, revealed some of the most accurate measurements of neutrino behaviour to date. “This was a big victory for our field,” said Mahn. “It shows we can work together to explore neutrinos in new ways.”

Both experiments fire intense beams of neutrinos through near and far detectors to track their transformations. Though T2K and NOvA share similar scientific goals, their distances and energies differ, making their data complementary. By combining their results, scientists managed to achieve higher precisions than any one of them could have done alone.

What Makes Neutrinos So Mysterious?

Neutrinos are among the most abundant but least understood particles in the universe. They have tiny masses and almost never interact with other matter.

“Hundreds of trillions pass through your body every second,” explained MSU postdoctoral researcher Joseph Walsh. “But almost none will interact.”

Physicists believe neutrinos could explain why the universe contains more matter than antimatter. The key may lie in neutrino oscillation, the process where neutrinos switch between types or “flavours” as they move. Understanding these oscillations could reveal if neutrinos and antineutrinos behave differently — a possible sign of charge-parity (CP) symmetry violation.

Does the Universe Favour One Neutrino Type?
The combined results showed no clear preference between the two possible mass orderings of neutrinos — normal or inverted. Under normal ordering, two mass states are light and one heavy, while the inverted case flips this balance.

If future studies confirm the normal ordering, researchers say more data will be needed to determine whether neutrinos violate CP symmetry. But if the inverted ordering proves true, the latest results suggest neutrinos might indeed behave differently from their antimatter counterparts.

Such asymmetry could explain why matter survived after the Big Bang. Without CP violation, physicists warn, we may lose our strongest clue to why the universe exists at all.

Collaboration Across the Globe
The NOvA team includes over 250 scientists and engineers from 49 institutions in eight countries, while T2K involves 560 members from 75 institutions in 15 countries. The collaborations began the joint analysis in 2019, combining eight years of NOvA data with ten years from T2K.

“These results are an outcome of cooperation and mutual understanding,” said T2K researcher Tomáš Nosek. “Both teams bring unique expertise in neutrino physics and technology.”

Both experiments continue to collect data, and scientists are already preparing updates. As Mahn noted, this collaboration may be the key to unlocking one of the universe’s oldest and deepest mysteries.