How 'Ghost Particles' Might Explain Why Anything Exists — Two Neutrino Experiments Join Forces

How neutrinos could help explain why matter won after the Big Bang

One of physics’ deepest mysteries is why the universe contains matter at all. According to CERN, matter and antimatter are produced in pairs and annihilate on contact, leaving only energy. If annihilation had dominated in the hot, early universe, little or no matter would remain — yet clearly it did. Understanding how matter came to outnumber antimatter is central to explaining our existence.

Neutrinos — nearly massless, weakly interacting particles often called “ghost particles” — are a promising lead. Trillions pass through your body every second but almost never interact, which makes them hard to study. Still, their subtle behavior, including oscillations between flavors (electron, muon and tau), could hide the key to why matter prevailed.

Two experiments, one joint analysis

Researchers from two long-baseline neutrino experiments, T2K in Japan and NOvA in the United States, combined their datasets and published a joint analysis in Nature. By merging differently designed detectors and complementary measurements, the collaboration improves statistical power and reduces some experimental ambiguities that each experiment faces alone.

“By making a joint analysis you can get a more precise measurement than each experiment can produce alone,” said Liudmila Kolupaeva, a NOvA collaborator and co-author.

What they measured: neutrino mass ordering and CP symmetry

The team focused on neutrino mass ordering — the question of whether the three neutrino mass states (ν1, ν2, ν3) follow a “normal” pattern (two lighter, one heavier) or an “inverted” pattern (two heavier, one lighter). Mass ordering affects oscillation probabilities and how experimental results map onto the CP-violating phase, a parameter that determines whether neutrinos and antineutrinos oscillate differently.

Detecting CP violation in the neutrino sector would be a crucial ingredient in explaining the matter–antimatter asymmetry, because it provides a mechanism whereby matter and antimatter behave differently. Determining the mass ordering reduces degeneracies in measurements of that CP-violating phase.

Results and significance

The combined NOvA + T2K dataset did not decisively prefer normal or inverted ordering, so the core cosmological mystery remains unresolved. However, the collaboration is a major methodological victory: it shows that large-scale experiments can pool data to tighten constraints and prepare the field for next-generation facilities like DUNE and Hyper-Kamiokande.

“This was a big victory for our field,” said Kendall Mahn, T2K co-spokesperson and co-author. “This shows that we can do these tests, we can look into neutrinos in more detail and we can succeed in working together.”

Future runs with higher statistics, improved systematics, and upcoming detectors will further narrow the possibilities and may reveal whether neutrinos played a decisive role in creating the matter-dominated universe we inhabit.