Astrophysical neutrinos

KM3NeT (Cubic KiloMetre Neutrino Telescope) is both a research infrastructure and a collaboration between research institutes. It comprises two gigantic neutrino telescopes installed on the Mediterranean seabed off Toulon and the southern tip of Sicily. Large water volumes are instrumented with optiques modules able to record the Cerenkov light produced by the neutrino interactions with matter.

The instruments

One of these instruments ORCA (Oscillation Research with Cosmics in the Abyss) is looking at neutrino fundamental properties (number, mass hierarchy) while the other ARCA (Astroparticle Research with Cosmics in the Abyss) is dedicated to cosmic neutrino observation.

To detect the produced light, optical modules have been developed that include 31 photomultipliers and their digitizing and control electronics. Modules are grouped by 18 to form lines (detection units). 115 detection strings are expected to form the ORCA telescope while 230 detection strings will be needed to complete the ARCA telescope. KM3NeT is currently under construction.

The first detection units have been immersed in 2017. KM3NeT is currently under construction. In 2025, ORCA contains almost 30 strings while ARCA have more that 50 deployed strings. After few years of construction, the two telescopes will reach their nominal sizes and their full observation capabilities.

An ultra high-energy astrophysical neutrino KM3-230213A has been observed in 2023 in the ARCA telescope while it had only 20 detection strings at that time.

The collaboration

Since February 2017, Subatech is a full member of the collaboration KM3NeT with about 50 other research institutes (mostly European) including 6 laboratories of in2p3 (APC, CPPM, IPHC, LPC-Caen, LUPM et SUBATECH).

Our activities

The team from Nantes includes physicists, technicians and engineers, participating in all the various activities connected to these instruments:

construction of optical modules,
ORCA string deployments,
orientation and position calibration of the modules,
software and distributed computing development,
automated and massive data processing,
data analyses and physic interpretation.

On the later, a thesis work is undergoing on multi-messenger astronomy: a search for coincidence between high energy neutrinos and fast radio bursts (FRB).

References

Contact : Lilian martin (lilian.martin@subatech.in2p3.fr)

The internet site of the KM3NeT collaboration : https:www.km3net.org

A recent review on the status and the results of KM3NeT presented at ICRC 2025 in Geneva.