National Institute for Nuclear Physics
INFN_logo-bianco-svg 4_LOGO_INFN_CON_NOME_ESTESO_INVERTITO-ai National Institute for Nuclear Physics

KM3NET

Km3net is the most extensive underwater research infrastructure in astroparticle physics in the world. Located deep in the Mediterranean Sea, it houses two neutrino telescopes: ARCA off the coast of Capo Passero in Sicily and ORCA off the coast of Toulon, France.

Neutrinos are among the most abundant and elusive particles in the universe: in number they are second only to photons.  While, on the one hand, their ability to pass through matter almost completely undisturbed makes them very difficult to observe (every second, billions of neutrinos from the Sun pass through our bodies, without us noticing), on the other, it characterises them as carriers of valuable information for studying the distant universe and dense astrophysical objects such as the centre of the Sun or stars.

Km3net/Arca studies high-energy neutrinos generated in the most violent cosmic processes. The goal is twofold: study their fundamental properties and observe the most powerful astrophysical sources in the Galaxy, such as Supernovae, and in the deep universe, such as active galactic nuclei and gamma ray bursts. Observing neutrinos originated from these sources will make it possible to study the origin of cosmic rays and the evolution of the more distant universe, going back to eras close to the Big bang, in an approach complementary to that used by particle physicists with CERN’s LHC accelerator in Geneva.

The underwater infrastructure

The ARCA detector consists of an array of strings, called detection units (DU), anchored to the seabed. In the final configuration, ARCA will include approx. 230 detection lines distributed at 100 mt of distance one from each other with a height of nearly 700 mt. Each detection line hosts nearly 560 ultrasensitive light detectors (photomultipliers) installed on 18 optical modules distributed vertically along each string. Currently (February 2025) 57 detection lines are active and taking data, equipped with a total of more than 30,000 photomultipliers.

The ORCA detector, instead, will include 115 lines of detection Units distributed at 20 mt of distance one from each other and with a height of nearly 200 mt.

Indeed, the two devices are optimised for very different experimental purposes: ARCA (Astronomy Research with Cosmic rays in the Abysses) is aimed at searching for cosmic neutrinos up to extreme energies, while ORCA (Oscillation Research with Cosmic rays in the Abysses) is dedicated to the study, with lower energy events, of so-called neutrino oscillations.

Artist’s impression of the KM3NeT detector with the mulit-PMT optical module (© KM3NeT collaboration)
KM3Net optical module installed in the sea (© KM3NeT collaboration)

In addition, the underwater infrastructure allows the connection of observatories dedicated to earth and sea sciences and is therefore also a valuable multidisciplinary laboratory, managed in collaboration with other European research infrastructures such as EMSO-ERIC.

The international collaboration

KM3NeT is an international collaboration of approx. 360 researchers from nearly 68 institutions of 22 countries. The project is included in the European roadmap of major research infrastructures (ESFRI – European Strategy Forum on Research Infrastructures). INFN is among the major research organisations engaged in KM3NeT, with research groups at the National Laboratories of the South and at the Bari, Bologna, Catania, Genoa, Naples with the related group in Salerno, and Rome sections, in collaboration with the corresponding universities.

Funding and economic impact

The research infrastructure is included in the European ESFRI, European Strategy Forum on Research Infrastructure, plan, the Italian National Research Infrastructure Plan (PNIR), and the Research Infrastructure (RI) plan of the Sicilian Region.

The construction of the Italian infrastructure has been possible thanks to the guidance and support of the INFN, with funds from the FOE Ordinary Fund for Research Bodies of the MUR Ministry of University and Research, and several national funding programs: PON (KM3NeT_IT and PACK) and POR of the Sicilian Region (IDMAR Project), as well as Design and Preparatory Phase projects funded by the European Community, and the involvement of many Italian companies in the sector of mechanics, electronics, imaging and, more generally, submarine technologies. The INFN, through funding from the PON KM3NeT_IT and PACK) and POR Sicilian Region (IDMAR Project), has already made investments for the construction of ARCA for 95 million euros. In particular, thanks to the IDMAR project, a decisive push was given to the construction of the first phase of the telescope and its preparation for final completion. Thanks to the financing of an additional 67 million euros, from PNRR funds of Mission 4 coordinated by MUR dedicated to the strengthening of large research infrastructures, the ARCA infrastructure will be able to become the largest neutrino telescope in the world.

 

Installation of ARCA (Astroparticle Research with Cosmics in the Abyss) apparatus by the KM3NeT scientific collaboration at the abyssal site off the coast of Capo Passero, Sicily. (© KM3NeT collaboration)
For more information, visit the project website