KM3NeT - News Archive

Archive of news items

KM3NeT has met in Les Houches for its Third Town Hall Meeting

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!

A new PMT for the KM3NeT detectors

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.

A set of dedicated studies on KM3-230213A

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.

Read the full article here: https://arxiv.org/abs/2502.08173

 

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.

Read the full article here: https://arxiv.org/abs/2502.08387

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!

Read the full article here: https://arxiv.org/abs/2502.08484

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.

Read the full article here: https://arxiv.org/abs/2502.08508

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.

Read the full article here: https://arxiv.org/abs/2502.08508

Limits on the violation of the Lorentz principle (see the article for full details)

Observation of an ultra-high-energy cosmic neutrino with KM3NeT

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.

More information can be found in the:

Additionally, 4 companion papers have been published on arXiv:

Tau neutrinos and neutrino mixing with ORCA6

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.

The paper is submitted to the Journal of High Energy Physics.

A preprint is available at arXiv 2502.01443

In the figures a comparison of our results with those from other experiments.

A fruitful Collaboration Meeting in Louvain-la-Neuve!

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.

 

 

 

 

Probing for invisible neutrino decay with ORCA6

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).

Sneak peek into the KM3NeT labs: Nikhef

17 January 2025 – Today we start a series of items highlighting the work of our technical staff in the labs of KM3NeT. Numerous technicians and engineers are working on the construction of the ARCA and ORCA detectors of the KM3NeT neutrino telescope. Together, but in distributed labs, they design and build the many detector components, assemble them into thousands of optical modules and integrate them into hundreds of deployment-ready detection units. It requires high standards of quality control and logistics between the labs.

Spotlights on the Nikhef lab

In this first item we set the spotlights on the KM3NeT production lab of the Nikhef institute in Amsterdam, The Netherlands. It is the lab where our multi-PMT optical module was born and it is one of the first production labs in KM3NeT.

Video’s in this item: Courtesy Nikhef – Marco Kraan. He has filmed the full process of assembling an optical module at Nikhef. Below we use his collection of short video clips.

“You just have to get the hang of it” according to Menno de Graaff, electronics engineer featuring in the clips.

The KM3NeT multi-PMT optical module is the key component of the neutrino telescope. It is a complex sensor module that registers the Cherenkov light from the charged particles from neutrino interactions with the seawater and monitors the position of the module in the deep sea. All sensors and the electronic boards for their power and readout are densely packed in a pressure resistant glass sphere. Therefore, assembly of the module requires highly skilled technicians.

(Compilation video (3min))

Step 1 – The assembly of an optical module starts with the empty pressure resistant glass hemispheres.

Step 2 – In the top hemisphere an aluminum cooling ‘mushroom’ is glued to the glass using a gel, which is applied in layers to avoid bubble forming in the gel. Once in the deep sea the cooling mushroom will keep the temperature in the optical module below 30 degrees.

Step 3 – In the bottom hemisphere an acoustic sensor is glued to the glass using a hard adhesive for good contact with the glass. The sensor is part of the acoustic system used to monitor the position of the optical module in the deep sea.

Step 4 – Two electronic boards are installed in the cooling mushroom in the top hemisphere. One provides the electrical power to the sensors in the module. The other is the heart of the module – the central logic board that collects and digitises the signals of all sensors in the module and transmit the digitised data via optical fibres to the backbone cable of the detection unit that is connected to the electro-optical cable network toward the control station on the shore. The connection is made via a feedthrough in a hole in the glass hemisphere. It is carefully checked that the hole is leaktight after installation of the feedthrough.

Step 5 – On top of the central logic board a fibre tray is installed with the fibres that connect the board with the backbone cable of the detection unit.

Step 6 – Switch from the glass spheres to stacking the 31 photomultiplier tubes (PMTs). In the structure that later fills the top glass hemisphere, 12 PMTs are stacked leaving room for the cooling mushroom to pass. A reflective metal ring is put around each PMT to improve their light collection.

Step 7 – In the structure that later will be placed in the bottom glass hemisphere, 19 PMTs are stacked. Together the 31 PMTs form a ‘fly’s eye’ looking in almost all directions. The PMTs will ‘see’ the faint Cherenkov light of charged particles induced by neutrino interactions in the deep sea.

Step 8 – The structures filled with PMTs are placed in the prepared glass hemispheres and connected to the ‘octopus’ electronics boards which are placed in the space left between the PMTs. The hemispheres are ready for a functional test in the test room.

The two structures are connected through a test cable to verify the functional behaviour of the optical module before closing it. During the functional test, the PMTs, acoustic piezo sensor and a LED are verified to work according to specification. In addition, fibre and power connections are checked, as well as the temperature of the electronic boards.

Step 9 – Once the functional test is passed, the PMTs are fixed on their position in the glass sphere and the space between the PMTs and the glass is filled with a special highly transparent gel. This is necessary in order not to loose light during operation in the deep sea. The filling must be done with care to avoid forming of air bubbles in the gel. Air bubbles would distort the path of the light.

Step 10 – Time to close the two hemispheres. The trick is that the readout electronics boards of the PMTs in the lower hemisphere of the module must be mounted on the stem of the cooling ‘mushroom’ before closing the optical module. When everything is connected correctly, the module is closed and some air is removed from it to create a small underpression. Then the module is sealed with a sticky strip to prevent the two hemispheres getting loose during transportation or during deployment to the bottom of the Mediterranean Sea. Once in operation the two remain tightly close due to the high pressure in the deep sea. Finally, a collar for attachment to the supporting ropes of the detection unit is mounted.

Step 11 – The module is ready for connection to the electro-optical backbone cable of a detection unit. The backbone cable runs the full length of hundreds of metres along the detection unit. It comprises copper wires for electrical power and optical fibres for data transmission. The video clip presents a birds-eye view of two sets of the final product of 18 optical modules connected with a backbone cable.

Step 12 –  The 18 optical modules connected to a backbone cable are shipped to the labs in France or Italy, which will build a ready-to-deploy detection unit and load it onto a launching vehicle for deployment in the deep sea.

This marks the end of our highlight of the work of technicians and engineers constructing KM3NeT multi-PMT optical modules and detection units at Nikhef.

In a next edition we will report on the work of technical staff in other KM3NeT labs.

Interested in the technical details of the KM3NeT multi-PMT optical module? We published a paper here.

The KM3NeT Collaboration has elected a new Management Team!

13 December 2024 – During the last Collaboration meeting, the KM3NeT Collaboration has elected a new Management Team, who will serve for the two coming years. In addition to the new Institute Board Chair, prof Antoine Kouchner from UPCité, France elected last June, the following people will be leading the Collaboration as:

  • Spokesperson: Paul De Jong (Nikhef and University of Amsterdam, The Netherlands)
  • Deputy Spokesperson: Damien Dornic (CPPM/CNRS, France)
  • Physics and Software Manager: Rosa Coniglione (INFN-LNS, Italy)
  • Technical Project Manager: Antonio D’Amico (Nikhef, The Netherlands)

The transition from the current to the new Management Team will happen at the next Collaboration meeting at the end of January, celebrated with presents and pictures! Stay tuned!

Curious about who are the people behind the researchers?  We asked them to share a few words about themselves!

 

Paul De Jong – Spokesperson:

“I studied Applied Physics at the Twente University of Technology in Enschede, the Netherlands, and did my PhD at Nikhef and at the University of Amsterdam in the ZEUS collaboration at the HERA collider at DESY in 1993, on calorimeter construction and reconstruction software, and measurement of the hadronic energy flow in first HERA data.

I was then a postdoc in the L3 Collaboration at LEP, first employed by MIT, later as a CERN fellow, on the commissioning of, and track reconstruction software for, the newly installed endcap muon chambers on the L3 magnet doors. I worked on the Z-line shape in dimuon decays and on W physics (triple gauge couplings and mass) at LEP 2. I returned to Nikhef in 1999 with a sponsored tenure-track position, joined D0 at the Tevatron (electron reconstruction and top physics) and ATLAS at the LHC, where I spent most time, in construction of the silicon strip detector endcaps and their commissioning, and in searches for supersymmetry in ATLAS data.

I got tenure at Nikhef in 2003, was appointed professor at the University of Amsterdam (UvA) in 2008, and full professor in 2012; I served as the director of the (astro)particle physics division (IHEF) of the UvA Institute of Physics between 2015 and 2024, and as director of the full UvA Institute of Physics between 2017 and 2022. I have handed over the Nikhef KM3NeT group leadership to Dorothea Samtleben last year, and the directorship of IHEF to someone else this summer.

With KM3NeT we have embarked on an amazing project. It resonates with everyone I talk to, from the general public to students to people at funding agencies. We have employed more than 50 detection units and produced first results, and the discoveries coming not only show how well the detector works, but also how much there is still to explore in our field.”

Fun fact about Paul: He was member of the Particle Data Group where he co-authored several instances of the Review on Experimental SUSY Searches in the Particle Data Book!

 

Damien Dornic – Deputy Spokesperson:

 “I began my career as PhD student at the Pierre Auger Observatory before joining the ANTARES and KM3NeT collaborations in 2006, where I pursued two postdoctoral positions, first at CPPM in Marseille and then at IFIC in Valencia. In 2011, I was appointed a permanent research position at CNRS. During this period, I have acquired expertise in neutrino astronomy. I was coordinator of the multi-messenger analysis group in ANTARES between 2012 and 2017 and coordinator of the multi-messenger and transient analysis group in KM3NeT between 2017 and 2020. Between 2020 and 2025, I was the co-convener of the astronomy group of KM3NeT. I am also in charge of the implementation of the real-time analysis framework in KM3NeT. I have been a pioneer in the development of the neutrino follow-up program of ANTARES and have developed collaborations with plenty of international observatories.

 Fun fact about Damien: Beyond his work in neutrino astronomy, Damien is also involved in the construction of the ORCA detector, contributing to technical discussions and the integration of detection units!

 

Rosa Coniglione – Physics and Software Manager:


“In the first part of my career, I worked on experimental nuclear physics, spending many years developing and operating an apparatus to study heavy-ion collisions. A seminar at my institute opened up a new world for me: I was captivated by a new, at least for me, detector that employed particle physics technology to explore the cosmos. Inspired by this idea, I began my work with KM3NeT.

Since the inception of the Collaboration, I have dedicated all my time to KM3NeT. I contributed to the ARCA detector design through MC simulations and participated in the initial sensitivity estimates. For many years, I led the Astronomy group and oversaw data analysis since the early stages of the Collaboration (first for the prototype detection units and then during the initial phase of construction of the apparatus). I have served as the Deputy Spokesperson of the Collaboration for the past four years.”

Fun fact about Rosa: Despite being born in Sicily, she worked for many years in France before joining KM3NeT. She is as passionate about Paris as about neutrinos!

 

Antonio D’Amico – Technical Project Manager:

“My engagement with KM3NeT started in the early stages of the project and consisted of developing an optical transmission system for a future submarine neutrino detector. During the following 10 years, I was involved in the design of the various detector prototypes, along with their installation and commissioning.

Since 2011, I have been part of the design team of the optics work package, which I later coordinated from 2018 to 2022 as a member of the Project Steering Committee. During the same period, I have been responsible for the design, validation, procurement, installation, and commissioning of the optical transmission system of KM3NeT Phase 1.

Starting in 2019, the structure of the project coordination has been experiencing profound changes with the full establishment of the Project Office team, in which I was appointed as Project Control Officer (PCO) in 2022.”

Fun fact about Antonio: Antonio has been a member of KM3NeT since his master thesis, learning from, growing with and now leading the Collaboration!