KM3NeT - News Archive

Archive of news items

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!

KM3NeT welcomes newcomers at the 2024 Bootcamp

10 December 2024 – The KM3NeT Bootcamp 2024, held at the Erlangen Centre for Astroparticle Physics – ECAP,  took place last week, bringing together 56 enthusiastic participants from around the world in a hybrid format. Over four engaging days, the attendees, guided by 18 expert teachers, dived into the fundamentals of KM3NeT, gaining insights into its core principles and tools.

The agenda included foundational sessions on the KM3NeT collaboration and detector principles, as well as hands-on workshops in software development, data acquisition, simulations, and calibration. Advanced topics covered astronomy, cosmic rays, neutrino oscillations, and the study of dark matter. Participants also explored tools for effective coding, data quality and computing strategies.

This event served as more than an introduction—it welcomed newcomers into the KM3NeT community, inspiring them to contribute to the future of science.

We extend our heartfelt thanks to ECAP for their exceptional organization and support in hosting this event.

Here’s to the next generation of cosmic explorers!

Search for non-standard neutrino interactions with ORCA6

29 November 2024 – In a new paper with the title ‘Search for  non-standard neutrino interactions with the first six detection units of KM3NeT/ORCA‘ we search for Non-Standard Interactions (NSI) by investigating distortions of the standard oscillation pattern of neutrinos of all flavours.

For the study we used the first six detection units of ORCA and 433 kton-years of exposure. In a sample of 5828 events reconstructed in the 1 GeV−1 TeV energy range we did not find significant deviations from standard neutrino interactions, but were able to place constraints on the flavour structure of the NSI coupling at 90% confidence level.

The measured constraints on the parameters of the non-standard coupling are compatible with the current most stringent limits placed by other experiments.

The results constitute the first search for NSI conducted with KM3NeT.

The paper is submitted to the Journal of Cosmology and Astroparticle Physics.

A preprint is available at arXiv: 2411.19078

In the image:
90% CL constraints on the NSI-couplings inferred from this study in comparison with the results from other experiments.

 

 

Update of gSeaGen simulation software

23 November 2024 – In a new paper with the title ‘gSeaGen code by KM3NeT: an efficient tool to propagate muons simulated with CORSIKA’ we describe an open source solution for efficient simulation of cosmic-ray induced muons in neutrino telescopes.

For this, we adapted the gSeaGen code, which generates high statistic samples of simulated neutrino-induced events, detectable by neutrino telescopes.

Updated gSeaGen can now also process muons from cosmic-ray induced particle showers in the atmosphere, which are generated by the Monte Carlo simulation code CORSIKA.

The tracking of muons towards the simulated detector offers efficient re-use of the particle shower when a muon misses the detector. We added several other new functionalities for computational efficiency and user control.

We updated gSeaGen with KM3NeT in mind, but other under-ground, under-water, or under-ice experiments may profit from it as well.

The paper is submitted to Computer Physics Communications
A preprint is available at: https://arxiv.org/abs/2410.24115

In the image:
Sketch of the projection of the side area of the detector (the ‘can’) onto the sea surface.