KM3NeT - News Archive

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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.

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 distortions of the standard oscillation pattern of neutrinos of all flavours. These distortions may be caused by Non-Standard Interaction (NSI) in the forward scattering of neutrinos inside Earth matter.

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.

The measured constraints on the parameters of the non-standard coupling are comparable 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.

Astronomy potential of ARCA

22 November 2024 – In a paper with the title  ‘Astronomy potential of KM3NeT/ARCA’ we present improvements that indeed enhance the astronomy potential of the ARCA detector.

An important  scientific objective for constructing the ARCA detector is the detection of high-energy cosmic neutrinos from point-like sources.  Scattering off the quarks inside a nucleon, neutrinos induce hadrons that generate a shower of particles. In so-called charge current interactions also a charged lepton is produced: a muon, electron or tau. These leptons have different signatures in the detector. Muons traverse the detector with a straight track of light, while electrons and taus generate outburst of light in the detector. This results in two main event detection signatures: track-like or shower-like events.

With the ARCA detector, we can use both detection signatures for investigating the Southern Sky, where many neutrino sources are expected along the Galactic Plane. For this we further improved the neutrino event selection method and the event reconstruction software of both track-like and shower-like events.

Simulations show that the improvements enhanced the sensitivity and discovery potential of ARCA for neutrino sources by 5-15%.

The paper is published in EPJ-C:

Eur. Phys. J. C 84, 885 (2024)

DOI: 10.1140/epjc/s10052-024-13137-2)

 

In the image (click on the image for a better resolution):

The ARCA point-like source sensitivity (black curves) as a function of sin(δ) (δ is the declination angle) with γ = 2.0 (γ is spectral index, which matches the energy spectrum of cosmic rays undergoing Fermi acceleration) . For comparison, the results of 15 years of observation with the ANTARES telescope (green curve) and 7 and 10 years of of observation with the IceCube telescope (red curves) are also shown.

First searches for Dark Matter

20 November 2024 – In a new paper with the title ‘First searches for Dark Matter with the KM3NeT Neutrino Telescopes’ we present limits for neutrino production by Dark Matter annihilation in the Sun and the Galactic Centre. For the analysis we used the data of early configurations of the ARCA and ORCA detectors of KM3NeT.

We tested for different dark matter masses, spanning from a few GeV/c^2 up to 100 TeV/c^2, but did not find a dark matter signal in the data of ARCA from the direction of the Galactic Centre. Instead, we set a limit on the self-annihilation cross section of dark matter into five different Standard Model particles, for the different dark matter masses tested.

In the data of ORCA we did not find a dark matter signal from the Sun. In this case, we could set a limit on the cross section of the scattering process between dark matter and nucleons.

The paper is submitted to JCAP. A pre-print is stored at the arXiv: https://arxiv.org/abs/2411.10092

In the image:
90% CF upper limits on the thermally-averaged Weakly Interacting Massive Particles (WIMPs, candidate Dark Matter particles) annihilation cross section as a function of the WIMP mass for the τ+τ– annihilation channel. The limit was obtained using data sets from the ARCA8, ARCA19 and ARCA21 configurations.  For comparison,  results obtained by other experiments are also shown.

KM3NeT gathered online for its fall collaboration meeting

13 November 2024 – Last week , the KM3NeT Collaboration has met online for its fall meeting.

During the meeting, we reviewed the current status of data taking for both ARCA and ORCA detectors, discussed the advancements in their construction, the progresses in MC simulation and detector calibration, and outlined the plans for the ongoing data analyses.

It was also the occasion to celebrate our two last sea campaigns and thus the expanded configurations of the detectors, ARCA 33 and ORCA24. The deployment of new instrumentation on the ORCA site will allow for a precise monitoring of the detector position and water properties.

During the meeting Antoine Kouchner started his mandate as chairperson of the Institute Board, taking over from Uli Katz: with many thanks to Uli for all the work done in the past years, and good luck to Antoine for his new duty.

Also during the meeting, the process to elect the new Management Team of the Collaboration was started.

Finally, KM3NeT gave a heartfelt greeting to its new members. Juan Antonio Aguilar Sánchez of the Université Libre de Bruxelles, Belgium, and Elisa Bernardini of Padova University, Italy,  joined as Observers, while the team led by Arthur Ukleja from the University of Krakow, Poland, was endorsed as Full Member. 

A warm welcome to everyone!

It was great to see the advancements in the physics analyses as well as the simulation and calibration works, to discuss recent scientific advancements and to see the Collaboration continue to grow.

The next Collaboration Meeting is scheduled for January, in Belgium, at Louvain-la-Neuve.

Quantum decoherence with ORCA6

30 October 2024 – Search for quantum decoherence in neutrino oscillations with six detection units of KM3NeT/ORCA

(KM3NeT paper, submitted to JCAP, arXiv: 2410.01388)

In a new paper we search for quantum decoherence in neutrino oscillations by looking for deviations of the standard neutrino oscillation pattern. We report upper limits on the decoherence parameters using data from ORCA6.

Usually, neutrino oscillations are studied in the framework of quantum mechanics assuming that the neutrino system is isolated. In this paper we study neutrino oscillations in the framework of open quantum systems, where the neutrino is coupled to a larger environment.

Several theories of quantum gravity postulate fluctuations in spacetime as a stochastic environment. A neutrino that propagates in such an environment will experience changes to its quantum phase. This will lead to a loss of coherence of the neutrino mass eigenstates during propagation. The phenomenon is referred to as decoherence in neutrino oscillations.

The search for decoherence in neutrino oscillations provides a rare opportunity to investigate quantum gravitational effects which are usually beyond the reach of current experiments.

The ORCA detector of KM3NeT is particularly designed to detect neutrinos generated in collision of cosmic ray particles with the Earth’s atmosphere. The atmospheric neutrinos are good probes to study oscillations and hence to search for quantum decoherence effects.

We used the neutrino data collected by the ORCA6 detector – an early detector configuration with six detection units –  in the period January 2020 to November 2021. In the analysis we focused on atmospheric neutrinos with energies of a few GeV to 100 GeV. We measured the parameters Γ21 and Γ31, that describe decoherence, assuming a power-law dependency on the neutrino energy Γij ∝ (E/E0)n and  explored two cases: with n = -2 and with n = -1.

Results

No significant deviation with respect to the standard oscillation hypothesis is observed. Therefore, 90% CL upper limits for the two cases are estimated as

The decoherence sensitivity of ORCA depends on the neutrino mass ordering. Therefore, we report upper limits for both normal and inverted ordering.

The results are comparable to bounds reported for IceCube/DeepCore and display the same dependency on the mass ordering.

In the figure below the 90% confidence level contours for Γ21 and Γ31 are shown for a decoherence model fitting both normal (NO) and inverted (IO) neutrino mass orderings.

 

Neutrino oscillations with ORCA6

29 October 2024 – Measurement of neutrino oscillation parameters with the first six detection units of KM3NeT/ORCA

(KM3NeT paper, accepted by JHEP, arXiv: 2408.07015)

In a new paper we show the potential of the ORCA detector: the measurements of neutrino oscillation parameters – with only 5% of ORCA’s final volume and during limited observation time – align with those from other experiments and are already becoming competitive.

Since the discovery of neutrino oscillations, the three-flavour neutrino model with non-zero neutrino masses has become well-established. The oscillation parameters are being measured with improving precision by several experiments world-wide. However, several questions persist. Among them the question what the value of the neutrino mixing angle θ23 is and the question whether the ordering of the three neutrino masses is “normal” (NO) with m1<m2≪m3 or “inverted” (IO) with m3≪m1<m2. KM3NeT has joined the effort to answering these questions using its ORCA detector.

Neutrinos created in collisions of cosmic ray particles with the Earth’s atmosphere are good probes to study the neutrino oscillations. The ORCA detector in the Mediterranean Sea is particularly designed to detect atmospheric neutrinos. Therefore, it is an optimal detector for the measurement of neutrino oscillation parameters.

However, the ORCA detector is still under construction.  The paper reports on the measurements with ORCA6 – an initial detector configuration that comprises six out of the foreseen 115 detection units. We extracted a high-purity neutrino sample, corresponding to an exposure of 433 kton-years. The sample of 5828 neutrino candidates was analysed following a binned log-likelihood method in the reconstructed neutrino energy and the cosine of the zenith angle.

Results

The atmospheric oscillation parameters measured with ORCA6 for both normal (NO) and inverted (IO) neutrino mass ordering are:

The inverted neutrino mass ordering hypothesis is disfavoured with a p-value of 0.25.

The 90% confidence level contours for the fitted oscillation parameters are shown in the left figure below with a solid line assuming normal ordering (NO)  and a dashed line assuming inverted ordering (IO).

In the figure at the right you find a comparison of the contour – assuming NO – with the corresponding contours measured by other experiments. The ORCA contour aligns with those other measurements and,  moreover,  it shows that ORCA is becoming competitive.