KM3NeT/ORCA telescope finds no Lorentz invariance violation in 5,828 neutrino events

Researchers of the international KM3NeT collaboration analysed 5,828 atmospheric neutrino candidate events detected by KM3NeT/ORCA, an underwater neutrino telescope in the Mediterranean Sea, according to miragenews.com. They found no evidence of a violation of Lorentz invariance, but set new experimental limits on how large such effects could be miragenews.commiragenews.commiragenews.comOpen source ↗. The results are published in the Journal of Cosmology and Astroparticle Physics (JCAP) miragenews.commiragenews.commiragenews.comOpen source ↗.

Why test Lorentz invariance

Lorentz invariance, the principle that the laws of physics are the same everywhere in the Universe, underlies Einstein's theory of relativity. Some approaches to quantum gravity, which seeks to reconcile general relativity with quantum physics, suggest that spacetime may consist of extremely small discrete units. This could lead to violations of Lorentz invariance miragenews.commiragenews.commiragenews.comOpen source ↗.

"We still don't know whether our spacetime is continuous or might be discrete," said Alba Domi of the Erlangen Centre for Astroparticle Physics (ECAP), one of the two corresponding authors. Neutrinos rarely interact with matter and can travel enormous distances, and they change flavour as they travel, a phenomenon called neutrino oscillation. The probability of these transformations can be predicted with high precision, so a deviation from the prediction could point to new physics miragenews.commiragenews.commiragenews.comOpen source ↗.

Data, limits and detector

The team analysed 1.4 years of data from the first six detection units of KM3NeT/ORCA. They compared observed neutrino energies and arrival directions with theoretical predictions miragenews.commiragenews.commiragenews.comOpen source ↗. The absence of a signal does not make such violations impossible: the result only limits how large certain effects could be without contradicting the observations miragenews.commiragenews.commiragenews.comOpen source ↗.

According to the authors, the limits, obtained with an early, partial configuration of the detector, are competitive with those of long-running experiments such as IceCube and Super-Kamiokande. They also include the first direct limits on certain possible effects involving the muon and tau neutrino flavours and the oscillations between them miragenews.commiragenews.commiragenews.comOpen source ↗. Lukas Hennig, a PhD student at ECAP and the other corresponding author, said that more data and a larger detector would allow a search for even smaller effects miragenews.commiragenews.commiragenews.comOpen source ↗.

ORCA lies about 40 km off the coast of Toulon, France, at a depth of approximately 2,450 metres, and studies atmospheric neutrinos. Its counterpart ARCA, off Sicily at about 3,500 metres, focuses on much higher-energy neutrinos from astrophysical sources. The researchers hope to extend the analysis to ARCA, but Domi noted that there are not yet enough astrophysical neutrino events for it miragenews.commiragenews.commiragenews.comOpen source ↗. The work was funded under a Marie Skłodowska-Curie fellowship of the Horizon Europe programme miragenews.commiragenews.commiragenews.comOpen source ↗.