3 February 2025 – In a new paper with the title ‘Probing invisible neutrino decay with the first six detection units of KM3NeT/ORCA’ we presents the results of a search for signs of invisible neutrino decay.
For the study we used the data collected with ORCA6 – the first six detection units of the ORCA detector. During 2020 and 2021, we collected a neutrino sample of 5828 neutrino candidates. Using a binned log-likelihood analysis, we searched for invisible neutrino decay, assuming an oscillation scenario with three neutrino-flavours, where the third neutrino mass state ν3 decays into an undetectable state such as a sterile neutrino.
The analysis yields a best-fit value for the invisible neutrino decay parameter of 
favouring a scenario with normal neutrino mass ordering and Θ23 in the second octant. The results are compatible with the Standard Model within a 2.1 σ interval, meaning that we found no significant evidence of new physics beyond the Standard Model. The constraint on the invisible decay parameter is compatible with data from long-baseline neutrino experiments and is of the same order of magnitude. It shows the potential of the full ORCA detector for probing scenarios beyond the Standard Model.
The paper is submitted to the Journal of High Energy Physics.
A preprint is available at arXiv: 2501.11336
In the image:
Average upper limits at 90% CL for the invisible neutrino decay parameter of ORCA compared to published combined fits (in blue) and future experiments (in black).
