The collaboration merged data from both experiments to refine measurement of neutrino properties. These elusive subatomic particles travel through the universe with minimal interactions. By integrating findings, the team delivered more accurate measurements of neutrino oscillation, where neutrinos change types-known as flavors-as they travel. The research sets groundwork for future studies that may clarify universe formation mechanisms or challenge current physics theories.

Kendall Mahn, an MSU physics and astronomy professor and T2K co-spokesperson, noted the achievement in uniting global efforts to enhance scientific outcomes: "This was a big victory for our field. This shows that we can do these tests, we can look into neutrinos in more detail and we can succeed in working together."

Initial conditions in the universe indicate matter and antimatter should have been equal and mutually annihilated. However, the persistence of matter points to unknown factors, potentially linked to neutrino behavior. Neutrino oscillation can reveal asymmetries, shedding light on why matter dominates.

MSU postdoctoral associate Joseph Walsh explained the challenge: "Neutrinos are not well understood. Their very small masses mean they don't interact very often. Hundreds of trillions of neutrinos from the sun pass through your body every second, but they will almost all pass straight through. We need to produce intense sources or use very large detectors to give them enough chance to interact for us to see them and study them."

Both T2K and NOvA are long-baseline experiments, sending neutrino beams through near and far detectors to compare behavior data across distances. Their distinct setups allowed the joint analysis to use complementary features, producing more robust results. NOvA collaborator Liudmila Kolupaeva said, "By making a joint analysis you can get a more precise measurement than each experiment can produce alone. As a rule, experiments in high-energy physics have different designs even if they have the same science goal. Joint analyses allow us to use complementary features of these designs."

The study investigated neutrino mass ordering, a scheme that affects oscillation probabilities. Normal ordering boosts muon neutrino oscillation to electron neutrino; inverted ordering, the reverse. An asymmetry between neutrino and antineutrino oscillations could indicate charge-parity (CP) symmetry violation-neutrinos behaving differently from antimatter.

Results showed neither mass ordering is favored at present. If mass ordering is inverted, the data provides evidence that neutrinos violate CP symmetry. Absence of such violation would challenge current explanations for matter's dominance. These joint results represent progress but do not completely resolve the mysteries of neutrino physics.

The collaboration included hundreds of scientists across countries and years of data. Both experiments continue collecting new information, with plans to update analyses in future cycles. T2K collaborator Tomas Nosek described the cooperation as "an outcome of a cooperation and mutual understanding of two unique collaborations, both involving many experts in neutrino physics, detection technologies and analysis techniques, working in very different environments, using different methods and tools."

Research Report:Joint neutrino oscillation analysis from the T2K and NOvA experiments

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