Highlights during day-to-day KM3NeT research activities such as pitches for new papers, talks and posters during international conferences and (internal) workshops, comments on events in astroparticle physics and particle physics etc.
15 July 2025 – The European Physical Journal C has accepted for publication a new KM3NeT paper with the title ‘Measurement of the atmospheric νμ flux with six detection units of KM3NeT/ORCA‘.
For the study we used data recorded by the ORCA6 detector between January 2020 and November 2021. Using machine learning classification, we selected 3894 neutrino candidates and estimated the background from atmospheric muons less that 1%. We derived the atmospheric muon-neutrino energy spectrum using an unfolding procedure and found that the measured flux is in agreement with values measured by other experiments and with theoretical predictions.
To date, the ORCA detector has 28 detection units (ORCA28). We expect that our measurement of the atmospheric muon-neutrino flux will improve with more and more ORCA detection units installed.
The paper is available as a preprint at arXiv 2504.09119.
In the figures below the atmospheric muon-neutrino flux measured with ORCA6 as a function of neutrino energy: (a) in comparison with the HKKM14 model; (b) in comparison with the measurements of other experiments.
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.
03 July 2024 – In June, KM3NeT scientist participated to the XXXI International Conference on Neutrino Physics and Astrophysics (Neutrino 2024), held in Milan, Italy, and organized by the University of Milano – Bicocca, the University of Milan and the Istituto Nazionale di Fisica Nucleare (INFN).
As one of the largest conferences in astroparticle physics, neutrino physics and cosmology, it was the occasion to share latest findings, innovative concepts and future outlooks among experts of the field.
Isabel Goos at Neutrino 2024 (credits Neutrino2024)
During the conference, Isabel Goos, KM3NeT’s researcher at the University of Paris Cité, was awarded one of the four prizes for the best-poster award. In her poster, titled “KM3NeT’s sensitivity to the next core-collapse supernova”, she discusses how individual multi-PMT optical modules of KM3NeT can be used as standalone detectors for the detection of low-energy neutrinos from Core Collapsed Super Novae. It has been selected among 460 accepted posters, of which 319 eligible for this acknowledgement.
KM3NeT joins in congratulating Isabel on her great achievement!
In total, KM3NeT presented 17 posters, covering topics including neutrino astronomy, neutrino oscillations, dark matter & exotics, cosmic-ray studies and technologies for neutrino physics.
KM3NeT at Neutrino2024.
In addition, four members of the KM3NeT Collaboration had a plenary talk: João Coelho, who discussed the latests results from KM3NeT; Maurizio Spurio, debating open problems in neutrino astrophysics; Naoko Kurahashi Neilson, contributing on the present and future of high-energy neutrino astronomy, and Jürgen Brunner presenting future detectors for atmospheric neutrinos.
Neutrino 2026 will be held at the University of California – Irvine. Looking forward to sharing our advancements also on that occasion!
The search focuses both on MeV neutrinos and high-energy neutrinos. No significant excess was observed for any of the sources. Upper limits on the neutrino emission from individual sources and the typical emission from binary black hole mergers were computed and compared with the constraints from other neutrino telescopes.
In particular, this study is applied to Starburst Galaxies, demonstrating that the ARCA detector, when completed, can trace TeV neutrinos from these sources. For instance, with ARCA it will be possible to discriminate between different astrophysical components in NGC 1068 after 3 years of data taking, strengthening the observations of the IceCube Neutrino Observatory.
In the pictures: (left) the sensitivities of the ARCA detector after 10 years of operation as a function of neutrino energy, compared to measurements of the IceCube neutrino observatory; (right) the discovery neutrino flux as a function of operation time.
3. Powering optical modules – a technical paper. The optical modules in the KM3NeT neutrino telescope in the deep Mediterranean Sea receive electrical power from the control station on the shore. An electronics board – dubbed the Power Board – in each optical module is described in the paper ‘The Power Board of the KM3NeT Digital Optical Module: design, upgrade, and production’. The board arranges powering individual components in the module at different voltage levels. The Power Board has been subjected to rigorous test to ensure reliable operation in the deep sea for more than a decade.
In the picture a photo of the Power Board with the various DC/DC converters generating the voltages needed.
20 November 2023 – Recently, KM3NeT published on the arXiv pre-prints of two new papers:
1 – Embedded software of the KM3NeT Central Logic Board
This KM3NeT technical paper describes the embedded software running in the data acquisition of the telescope. Located in the deep Mediterranean Sea, the hardware of the telescope is not directly accessible. The implemented software facilitates remote management of the deployed hardware and safe reconfiguration of firmware. It runs on the central electronics board of each optical module of the KM3NeT detectors. The central logic board coordinates the readout of all equipment inside the module and manages the communication and data transmission over optical fibers connecting the module to the control station on shore.
(Accepted for publication in Computer Physics Communications)
2 – KM3NeT neutrino follow-up of gravitational wave sources
In this paper the KM3NeT Collaboration reports the results of a neutrino follow-up study made with ORCA data of gravitational wave sources detected by LIGO–Virgo in 2019-2020. The search focuses both on MeV neutrinos and high-energy neutrinos. No significant excess was observed for any of the sources.
Upper limits on the neutrino emission from individual sources and the typical emission from binary black hole mergers are computed and compared with the constraints from other neutrino telescopes.
Since May 2023, the Collaboration is performing real-time follow-ups of the GW triggers detected by LIGO-Virgo-KAGRA in their fourth observing run, with both ORCA and ARCA detectors with much larger instrumented volumes than in the previous searches.
In the figure the comparison of 90% upper limits on the neutrino fluence from gravitational wave sources for ANTARES, IceCube, Super-Kamiokande and KM3NeT.
The ICRC is the International Cosmic Ray Conference. It is one of the major conferences in astroparticle physics and covers many subfields. In 2023, the 38th International Cosmic Ray Conference (ICRC) took place in Nagoya, Japan.
KM3NeT researchers actively participated to present the work of the Collaboration and many contributions to the proceedings of the conference were published. The full proceedings of ICRC2023 can be found at here. Below you find the individual KM3NeT contributions, categorised in the various scientific and technological fields.
15 September 2023 – This summer, KM3NeT members participated in conferences all over the world to present the latest results and developments of our Collaboration.
Besides TAUP in Vienna, EPS-HEP in Hamburg, and TeVPA in Naples, KM3NeT-ers have massively attended the 38th International Cosmic Ray Conference (ICRC), in Nagoya, Japan. Since the ICRC is among the largest conferences in the field of astroparticle physics, it was an ideal opportunity for reporting the progress of the collaboration in neutrino astronomy, neutrino physics, multi-messenger astronomy, cosmic rays, and dark matter searches.
In total, KM3NeT presented 10 talks and 28 posters at the ICRC, in addition to a plenary talk given by prof. Antoine Kouchner, the spokesperson of the ANTARES Collaboration, on catching neutrinos in the Mediterranean Sea.
Interested?
The full proceedings of ICRC2023 can be found here. For your convenience, the contributions of KM3NeT to the proceedings are available here and are also on arXiv: https://arxiv.org/abs/2309.05016.
KM3NeT members at the ICRC2023.Antoine Kouchner, spokesperson of the ANTARES Collaboration, presenting at the ICRC2023 an overview of recent work achieved by ANTARES and KM3NeT.Some of the talks given by KM3NeT members at the ICRC2023.Some of the posters presented by KM3NeT members at the ICRC2023.
29 June 2023 – The KM3NeT Collaboration congratulates the IceCube Collaboration after today’s announcement of an evidence in IceCube of high-energy neutrinos originating from our own Galaxy.
“Congratulations to the IceCube Collaboration for this great result. For the KM3NeT Collaboration it is a very important observation” says Paschal Coyle, the KM3NeT Spokesperson.
While IceCube has previously reported evidence for several sources of extragalactic neutrinos, the detection of neutrinos from the Milky Way has proved difficult, due to the IceCube’s location at the South Pole, where a signal from within our Galaxy is observed as downgoing events and is therefore subject to a large background of atmospheric muons. Furthermore, as the signal was observed in the cascade channel, which has a limited angular resolution, it was not possible to determine if the signal is due to a diffuse source or a collection of unresolved point sources.
A telescope located in the Northern hemisphere, such as KM3NeT, observes our Galaxy using upgoing events, which have significantly less background than downgoing events and are therefore easier to detect. This in fact allowed ANTARES to report the first hint of a neutrino emission from the Galaxy (see the news item on the ANTARES web-site).
Moreover, the KM3NeT telescope will be able to observe the signal in the muon neutrino channel in addition to the electron neutrino channel and both with a much better angular resolution than IceCube.
“IceCube has confirmed our Galaxy is a guaranteed source of high-energy neutrinos. KM3NeT looks forward to unravelling the origins of this Galactic signal with unprecedented precision” concludes Paschal Coyle.
1 February 2023 – Via a long-distance electro-optical network the more than 6000 optical modules of KM3NeT in the deep sea are provided with a point-to-point connection to the control station on shore. The optical layer is presented in full details:
The optical data transport system of the KM3NeT neutrino telescope at the bottom of the Mediterranean Sea will provide more than 6000 optical modules in the detector arrays with a point-to-point optical connection to the control stations onshore. The ARCA and ORCA detectors of KM3NeT are being installed at a depth of about 3500 m and 2500 m, respectively and their distance to the control stations is about 100 kilometers and 40 kilometers. In particular, the two detectors are optimised for the detection of cosmic neutrinos with energies above about 1 TeV (ARCA) and for the detection of atmospheric neutrinos with energies in the range 1 GeV–1 TeV (ORCA). The expected maximum data rate is 200 Mbps per optical module. The implemented optical data transport system matches the layouts of the networks of electro-optical cables and junction boxes in the deep sea. For efficient use of the fibres in the system the technology of Dense Wavelength Division Multiplexing is applied. The performance of the optical system in terms of measured bit error rates, optical budget are presented. The next steps in the implementation of the system are also discussed.
The architecture of the optical layer connecting the ARCA detector of KM3NeT in the deep sea with the control station on shore.
27 July 2022 – Long-term operation in the deep sea puts challenging requirements on detectors. A review of the design and construction of the KM3NeT optical module has been published:
The optical module of the KM3NeT neutrino telescope is an innovative multi-faceted large area photodetection module. It contains 31 three-inch photomultiplier tubes in a single 0.44 m diameter pressure-resistant glass sphere. The module is a sensory device also comprising calibration instruments and electronics for power, readout and data acquisition. It is capped with a breakout-box with electronics for connection to an electro-optical cable for power and long-distance communication to the onshore control station. The design of the module was qualified for the first time in the deep sea in 2013. Since then, the technology has been further improved to meet requirements of scalability, cost-effectiveness and high reliability. The module features a sub-nanosecond timing accuracy and a dynamic range allowing the measurement of a single photon up to a cascade of thousands of photons, suited for the measurement of the Cherenkov radiation induced in water by secondary particles from interactions of neutrinos with energies in the range of GeV to PeV. A distributed production model has been implemented for the delivery of more than 6000 modules in the coming few years with an average production rate of more than 100 modules per month. In this paper a review is presented of the design of the multi-PMT KM3NeT optical module with a proven effective background suppression and signal recognition and sensitivity to the incoming direction of photons.
Rendering of a KM3NeT optical module with bollards attached to mechanically supporting cables in the deep-sea. In the cut out, the interior of the module with photomultipliers and electronics is visible. The black break-out box connects to the electro-optical network for electrical power and long-distance data communication toward the control station on shore.
