16 May 2025 – This week at the ORCA site, a sea operation was performed with a twofold purpose: the recovery from the sea bottom of some oceanographic instruments which required some maintenance and the installation of a set of 4 new detection units. The number of detection units in ORCA has thus been increased to 28.
The field is getting crowded!
This is a sonar map of the ORCA site after the installation of the new detection units. Also marked in the image are the various components of the submarine infrastructure, comprising a junction box (“JB1”), a module for interface with oceanographic instrumentation (Module Interface Instrumented – MII) and a calibration structure (Calibration Base – CB).
As usual, the operation was performed with two ships: the Castor of Foselev, for deployment of the detection units, and the Janus II of SAAS (formerly Comex), equipped with the Apache deep-sea remotely operated vehicle, for submarine operations.
Everything worked very smoothly – many thanks to the crews offshore as well as to the team who performed the functional tests of the new detection units from the shore station!
14 May 2025 – Today the new facilities of the CAPACITY laboratory in Caserta have been inaugurated.
The extension of the CAPACITY laboratory will allow for building, testing and integrating a large fraction of the KM3NeT digital optical modules, base modules and detection units, thus considerably speeding up the construction of the KM3NeT detectors. The laboratory is in fact equipped to facilitate all the integration steps which are necessary for building complete detection units and for preparing them in the packed configuration used for deployment.
In addition, the CAPACITY laboratory hosts sophisticated test facilities, including a state-of-the-art laboratory dedicated to the characterisation of optical sensors, a large tank for tests of digital optical modules in water, a large thermal chamber and more, allowing for extensive tests of different components to be carried out at the site. The CAPACITY laboratory also hosts the European Logistics Center of the Collaboration, where the components needed for detector construction are collected for distribution to the integration sites.
CAPACITY (Campania AstroPArtiCle InfrastrucTure facilitY) is a laboratory created in 2019 thanks to the joint action of the Italian National Institute of Nuclear Physics (INFN) and the University of Campania “L. Vanvitelli”, within the Research Laboratories Centre (POLAR) of the Department of Mathematics and Physics of the University of Campania.
The new CAPACITY facilities have been made possible by the efforts of the institutions, the University of Campania “L. Vanvitelli” and the Italian National Institute of Nuclear Physics, in the framework of the NextGenerationEU Italian PNRR KM3NeT4RR project. With KM3NeT4RR, crucial actions towards the expansion of the KM3NeT Italian site off the coast of Capo Passero in Sicily have been funded. These include the extension of the submarine infrastructure and the strengthening of the detector integration laboratories and of its testing facilities.
Lucio Gialanella (left) and Pasquale Migliozzi (right), respectively the representative of University of Campania “L. Vanvitelli” and the CAPACITY director, at the inauguration time
Paul de Jong, KM3NeT Spokesperson
One of the new integration halls at CAPACITY (for DOM integration)
18 April 2025 – The third KM3NeT Town Hall Meeting took place in the School of Physics of Les Houches, close to Chamonix (France), in front of the Mont Blanc, from 13th to 18th April 2025.
The meeting brought together a vibrant community of scientists to exchange ideas, present recent progress, and build new external collaborations in the field of neutrino astronomy.
Held in person, the agenda featured plenary sessions in the mornings and interactive working groups in the afternoons, fostering deep discussions between experimentalists and theorists. This meeting structure proved highly effective in encouraging meaningful collaboration and idea-sharing across the astroparticle physics community.
Highlights of the meeting included updates on the status and performance of KM3NeT’s ORCA and ARCA detectors, as well as discussions on ultra-high-energy events (among which, of course, KM3-230213A), Galactic neutrino sources and neutrino follow-up strategies. Additionally, poster sessions showcased ongoing analyses and new research directions.
With its promising angular resolution, broad energy range and sky-coverage, KM3NeT is positioned at the forefront of the multi-messenger astronomy era. The Town Hall Meeting reinforced the groundwork for exciting future collaborations.
On a lighter note, the event also featured networking sessions on mountain trails, where participants enjoyed scenic trekking routes, and a surprising April snowfall, which added both charm and challenge to the experience.
A sincere thank you to all participants, speakers, and organizers for making this event a success. We look forward to continuing the momentum and welcoming you to future KM3NeT events!
7 April 2025 – We present a new paper with the title ‘Evaluation of the upgraded 3-inch Hamamatsu photomultiplier for the KM3NeT neutrino telescope’
In the paper we report the characteristics of a new photomultiplier tube for the KM3NeT detectors.
Our tests of more than 200 new Hamamatsu R14374-02 photomultiplier tubes (PMTs) show better quantum efficiency and more uniform response across the photocathode surface compared to the previous model.
We also measured a significantly better time performance of the new photomultiplier with cleaner, more precise signals and fewer delayed pulses and afterpulses.
This means sharper detection of the faint Cherenkov light generated by relativistic charged particles induced by neutrino interactions. In particular it means a lower noise level and overall a better performance of the KM3NeT neutrino telescope.
The upgrade of the optical modules of our detectors with this new 3-inch PMT represents yet another step forward for deep-sea neutrino astronomy!
The paper has been submitted to the Journal of Instrumentation and is available as a preprint at arXiv 2504.02989.
In the picture the instrumental setup in the CAPACITY lab with PMTs for two optical modules ready for tests in a dark box. In the inlay the distributions of the percentage of measured afterpulses and delayed pulses for the new R14374-2 PMTs (blue) and the old R12199-2 PMTs (green). The distributions of the new PMTs peak at lower values and are significantly narrower.
20 February 2025 – Recently the KM3NeT Collaboration has published evidence for the cosmic neutrino with the highest energy ever detected (the article on Nature can be accessed from here). This event is identified as KM3-230213A.
In a set of dedicated studies, the Collaboration has investigated the possible sources of the event and the implications that may be derived from it.
These studies are included in a set of articles which have recently been released:
The ultra-high-energy event KM3-230213A within the global neutrino landscape
The compatibility of the occurrence of KM3-230213A with the constraints placed by other experiments is explored.
On the Potential Galactic Origin of the Ultra-High-Energy Event KM3-230213A
The possibility that KM3-230213A may have originated in our Galaxy is discussed. The study did not allow to identify plausible mechanisms and sources which could sustain such hypothesis, leading to the conclusion that the neutrino is most likely of extra-Galactic origin.
Characterising Candidate Blazar Counterparts of the Ultra-High-Energy Event KM3-230213A
In this paper the possibility is explored that KM3-230213A may have originated in a distant blazar. The study concerned a set of 17 blazars, which were identified as plausible sources of high-energy neutrinos due to their multiwavelength properties, highlighting in particular three of them. This work involved plenty of facilities: KM3NeT, VLA, VLBA, RATAN-600, OVRO, Swift, Fermi, SRG/eROSITA, Gaia, CRTS, ATLAS, ZTF, WISE/NEOWISE, Chandra and ROSAT!
On the potential cosmogenic origin of the ultra-high-energy event KM3-230213A
The intriguing possibility that KM3-230213A may be of cosmogenic origin, i.e. it was originated from the interaction of ultra-high-energy cosmic rays with ambient photon and matter fields, is discussed in this paper, leading to hypotheses for reconciling the occurrence of this event with the latest measurements of cosmic rays of extreme energy.
KM3NeT Constraint on Lorentz-Violating Superluminal Neutrino Velocity
The Lorentz symmetry, the fundamental principle which states that nothing can go faster than the speed of light in vacuum, is tested in this study. By looking at the energy of KM3-230213A and the distance travelled, the difference between neutrino and light speed was constrained to less than 1 part in 1000 billion billion, which represents the most stringent limit ever set using this method of analyzing high-energy neutrinos.
On February 12, 2025, The KM3NeT Collaboration has announced the detection from the abyss of the Mediterranean Sea of a cosmic neutrino with a record-breaking energy of about 220 PeV.
6 February 2025 – We present a new paper with the title ‘A study of tau neutrinos and non-unitary neutrino mixing with the first six detection units of KM3NeT/ORCA‘.
Oscillations of atmospheric muon and electron neutrinos produce low-energy tau neutrinos, which can be observed by the ORCA detector of the KM3NeT neutrino telescope. For a first measurement we used the ORCA6 configuration, an early subarray corresponding to about 5% of the final detector. For the study we selected a sample of 5,828 neutrino candidates.
The measured ντ normalisation, defined as the ratio between the number of observed and expected tau neutrino events, is
This translates into a ντ charged-current cross section of
at a median ντ energy of 20.3 GeV. The result is consistent with the measurements of other experiments. In addition, we could improve the current limit on the non-unitarity parameter affecting the τ-row of the neutrino mixing matrix with α33 > 0.95 at 95% confidence level.
4 February 2025 – Last week, KM3NeT has met, both in person and online, for its winter Collaboration Meeting , in Louvain-la-Neuve, Belgium, hosted by UCLouvain.
Various discussions and presentations highlighted progresses and activities related to the ARCA and ORCA detectors, including updates on construction, simulation, calibration and data analysis efforts. The meeting also featured talks on the latest scientific results, including…plans for very exciting results to be announced soon!
Beyond the scientific sessions, the event fostered community engagement through social activities and networking opportunities.
It was also the occasion to welcome our new Management Team: Paul De Jong (Nikhef and University of Amsterdam, The Netherlands) serves as Spokesperson, Damien Dornic (CPPM/CNRS, France) as Deputy Spokesperson, Rosa Coniglione (INFN-LNS, Italy) as the Physics and Software Manager, and Antonio D’Amico (Nikhef, The Netherlands) holds the position of Technical Project Manager. The entire Collaboration extends its congratulations to the outgoing Management Team and wishes the best of luck to its newly elected members.
The KM3Net Collaboration is pleased to welcome a new team, from INFN and University of Florence, Italy, coordinated by Nicola Mori: we are happy to have you as part of our Collaboration and look forward to your valuable contributions.
Thanks a lot to the whole local team for the wonderful organization.
The next Collaboration Meeting is scheduled for the coming summer, in France, at Caen.
The KM3NeT Management team (from left to right): Damien Dornic, Paul De Jong, Rosa Coniglione and Antonio D’Amico.
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.
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).
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.
