KM3NeT - Recent News

Latest news items published on the home page.

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

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

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.

Welcome ARCA33 and ORCA24!

28 October 2024 – The latest sea campaigns at both the KM3NeT’s ARCA and ORCA sites have led to major progress in expanding detector installations and improving calibration systems.

The number of detection units in operation in the deep sea has been increased to 57: 33 in ARCA and 24 in ORCA.

Despite bad weather at the ARCA site, the so-called Phase-1 part of the apparatus was completed, while construction of Phase-2 was started with the installation of two new junction boxes, three detection units (exploiting a new data acquisition architecture), and calibration components. The operations also included important maintenance tasks, such as recovering and replacing acoustic beacons. All optical modules of the deployed strings are fully operational. KM3NeT/ARCA now comprises 33 detection units.

At the ORCA site, a 60-hour calm weather window allowed the team to deploy the Calibration Unit (Calibration Base+Instrumentation Unit) and to install an additional detection unit. After these successful installations, node 1 of ORCA is complete and fully functional, an important milestone in the construction of ORCA. The total number of functional detection units at ORCA has now reached 24.

These recent efforts at both sites underscore KM3NeT’s expanding capability in detecting and studying neutrinos from the sea’s depths. The whole Collaboration extends its gratitude to the offshore and onshore teams whose hard work made these successful operations possible.
A furled detection unit ready for the deployment at the ORCA site
ORCA offshore team on the Castor 02 ship
Components for ARCA on the deck of the Optimus Prime ship: in the foreground is one junction box, behind it there are a couple of spools with the submarine interlink cables and then some detection units
ARCA onshore shift crew at the site of Portopalo

 

 

 

 

 

 

 

 

 

 

 

ATLAS comet visible from the harbour of Portopalo di Capo Passero

 

Sonar scan of the ORCA site taken by the ROV at the end of the operation. The anchors of the detections Units (DUs), the junction box (JB1), the Calibration Base (CB), the Instrumentation Unit (IU) and the Module Instrumentation Interface (MII) are all visible.

Neutrino 2024 Poster Winner: Isabel Goos

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!