Researchers with the international KM3NeT collaboration analyzed 5,828 atmospheric neutrino candidate events detected by KM3NeT/ORCA deep in the Mediterranean Sea, finding no evidence of Lorentz invariance violation while setting new experimental limits on fundamental physics.
Phys.org reported that the findings, published in the Journal of Cosmology and Astroparticle Physics, establish direct constraints on possible behavioral differences between muon and tau neutrinos. The inquiry tests Lorentz invariance, the core principle of Einstein’s theory of relativity stating that physical laws remain identical everywhere in the universe.
Probing Quantum Gravity in the Mediterranean Depths
Physicists question this bedrock principle because reconciling general relativity with quantum mechanics remains one of modern physics’ steepest hurdles. Theoretical models of quantum gravity suggest that continuous spacetime might actually consist of discrete, extremely small units. Such a granular structure could trigger minute violations of Lorentz invariance.
“We still don’t know whether our spacetime is continuous or might be discrete,” said Alba Domi, a researcher at the Erlangen Centre for Astroparticle Physics (ECAP) at Friedrich-Alexander-Universität Erlangen-Nürnberg and a corresponding author of the study. “Looking for violations of Lorentz invariance is one way to investigate this possibility.”
Neutrinos serve as ideal probes for this search. These elusive subatomic particles rarely interact with ordinary matter, traversing astronomical distances and passing straight through the Earth. They also undergo neutrino oscillation, shifting between different flavors as they travel. Predictable oscillation patterns make any anomaly a potential signpost for new physics.
Researchers Evaluate Early Data from Six Detection Units
The research team evaluated 1.4 years of data gathered by the initial six detection units of KM3NeT/ORCA. By cross-referencing observed neutrino energies and arrival directions against theoretical models, the team searched for deviations.
No violations of Lorentz invariance surfaced in the dataset. Yet the analysis successfully bounded how large such hypothetical effects could be without contradicting empirical reality. Despite relying on an early and partial buildout of the deep-sea infrastructure, these constraints are competitive with those of long-running experiments such as IceCube and Super-Kamiokande.
For the first time, the collaboration placed direct bounds on Lorentz invariance violations involving muon and tau neutrinos during their oscillations. The project achieved these milestones while operating a fraction of its final scale.
“These results show the potential of KM3NeT/ORCA to test fundamental principles of physics, even with a relatively small detector,” said Lukas Hennig, a Ph.D. student at ECAP and the study’s co-corresponding author. “With more data and an expanding detector, we will be able to search for even smaller effects.”
Expanding the Deep-Sea Telescope Network
Construction on the KM3NeT/ORCA array continues off the Mediterranean coast as engineers deploy additional detection units. Future phases intend to use KM3NeT/ARCA, a sister configuration aimed at detecting ultra-high-energy neutrinos originating from distant astrophysical sources across the universe.
High-energy neutrino research gained broader recognition following the recent 2026 Nobel Prize in Physics awarded to Francis Halzen for his work with the IceCube Neutrino Observatory. As ARCA scales up and gathers more high-energy events, researchers plan to test relativity across even greater cosmological baselines where potential quantum gravity anomalies might become more pronounced.
