News from the experiments



ANTARES is smoothly taking data and continues to play a successful role in various multi-messenger and alert programs.  However, given the configurations of ORCA and ARCA now operating, the termination of ANTARES operation will happen at the next favorable occasion. The latter is not yet firmly scheduled.



A summer task force is preparing the next deployment season, including an additional building and other upgrade operations at the shore. Also, the implementation of new trigger options is studied, with the aim to improve the cluster sensitivity close to the horizon.  All eight clusters are taking data. Most optical modules for the two clusters to be deployed in the next season are ready (partially due to the deployment of only one cluster last season, due to extended repair operations).



The ARCA and ORCA detectors are taking data smoothly. The next sea operations are scheduled in September, with the hope to add five Detections Units (strings) to ARCA and seven to ORCA



South Pole operations for the 2021/2022 season are still heavily impacted by COVID. There is a high probability that this year's Upgrade season is zeroed out. That would move the planned upgrade with seven strings from 2022/2023 to 2023/2024. The two new Winterovers Wen Marie-Sainte and Moreno Baricevic (both with previous Polar experience at Concordia Station) will replace Josh and Martin, the present winterovers, while one or two additional persons will go down for several weeks to replace components in the IceCube Laboratory.  Cargo which IceCube has already in the pipeline, will hopefully move south, some of it at least. 


Aurorae and the Milky Way do not care about COVID, at least this is what we can conclude from the following pictures which Josh and Martin have sent us:


image1 copy copy copyIn the foreground is the ceremonial Pole with the flags and an exhausted winterover taking a dramatic rest between the flags. In the background is the South Pole station. Top left is the Milky way, top right an aurora. The bright object above the Norwegian flag is Jupiter while Saturn is just to the upper left of the New Zealand flag.


gnn00011.jpgThe Sun rises behind the IceCube Laboratory, you can also see the Milky Way and the Large Magellanic Cloud off to the side.


Martin and Josh do not only shoot great aurora pictures but are also working hard! See below Josh unscrewing DOM cables in order to replace a GPS card.




The KM3NeT collaboration has submitted a paper «Sensitivity to light sterile neutrino mixing parameters with KM3NeT/ORCA» to the Journal of High Energy Physics, JHEP (posted at  2107.00344.pdf ( The paper reports the sensitivity of ORCA to the presence of a light sterile neutrino in a 3+1 model. The following figures demonstrate that after three years of data taking, ORCA will be able to probe the active-sterile mixing angles θ14, θ24, θ34 and the effective angle θμe, over a broad range of mass squared difference Δm41² from 10-5 to 10 eV², allowing to test the eV-mass sterile neutrino hypothesis as the origin of short baseline anomalies, as well as probing the hypothesis of a very light sterile neutrino, not yet constrained by cosmology.


gnn00009.jpg99% C.L. KM3NeT/ORCA sensitivity to the mixing parameters θ24 and θ34, with Δm241 = 1 eV², for three years of assumed data taking. Sensitivity results are compared with current upper limits from ANTARES, IceCube/DeepCore and Super-K. The excluded region is the one on the right of the lines.



gnn00010.jpg99% C.L. KM3NeT/ORCA sensitivity to the mixing parameter θ24, assuming three years of data taking, compared with current upper limits from cosmology, MINOS/MINOS+, IceCube and Super-K.



99% C.L. KM3NeT/ORCA sensitivity to the mixing parameter |Uμe|2, assuming three years of data taking, compared with current upper limits from Daya Bay+Bugey-3+MINOS/MINOS+, KARMEN and NOMAD. Current anomaly regions from LSND and MiniBooNE are shown top left.


The JUNO and KM3NeT collaborations have submitted a joint paper «Combined sensitivity of JUNO and KM3NeT/ORCA to the neutrino mass ordering» to JHEP (posted at 2108.06293.pdf (

A combined analysis turns out to be more powerful than simply adding the sensitivities for both experiments. This is due to a tension arising in the  Δm31² measurement between JUNO and ORCA when the wrong neutrino mass ordering is assumed.

The combination significantly reduces the time required to reach a 5σ determination of the neutrino mass ordering for any value of the oscillation parameters. In all cases, a 5σ measurement can be obtained within 6 years for the combined analysis, compared to more than 10 years using only ORCA data, depending on the true ordering.

The gain in time is larger in cases where ORCA alone would require a longer time for reaching a 5σ sensitivity due to the uncertainty on the θ23 value. In the favorable case of the true normal ordering and in the second octant, a 5σ NMO determination would be feasible after less than 2 years of data taking with the combined analysis. In this favorable scenario, which also corresponds to the current global best-fit value, the neutrino mass ordering would be determined at least a year ahead of what can be done using only ORCA data (see the first of the following figures). Because the gain in time to reach the determination of the neutrino mass ordering in the combination of  JUNO and ORCA does not come exclusively from each experiment’s own ability to determine the neutrino mass ordering, the combination is sensitive to systematic uncertainties and detector effects in a different way than either experiment does independently. For instance, even if the JUNO energy resolution is critical for the measurement of the neutrino mass ordering using only JUNO data, it has only a small impact on the combined analysis (see the second figure below). Alternatively, changing the ORCA systematics between optimistic and baseline systematics has a small impact on the power of ORCA alone to determine the neutrino mass ordering, however, it has a larger impact on the combined analysis.



NMO sensitivity as a function of time for only JUNO (red), only ORCA (blue), and the combination of JUNO and ORCA (green), assuming baseline (solid) or optimistic (dashed) systematics.



The same as the previous figure, considering a better (dotted) and worse (dashed) energy resolution for JUNO than the nominal one (solid) by ±0.5% √ E/MeV.


The ANTARES collaboration has submitted a paper «Studying Bioluminescence Flashes with the ANTARES Deep Sea Neutrino Telescope» to Ocean Dynamics (posted at [2107.08063] ( The main authors come from the Information Field Theory Group, Max Planck Institute for Astrophysics, and Chair of Robotics, Artificial Intelligence and Real Time Systems, Technical University of Munich, both in Garching, and from Department of Astrophysics/IMAPP, Radboud University, Nijmegen.

The paper presents a novel technique to exploit the extensive data sets provided by underwater neutrino telescopes to gain information on bioluminescence in the deep sea. The paper proposes a statistical method that allows reconstructing the light emission of individual organisms, as well as their location and movement. A mathematical model is built to describe the measurement process of underwater neutrino telescopes and the signal generation of the biological organisms. The so-called “Metric Gaussian Variational Inference algorithm” is used to reconstruct the model parameters using the recorded photon counts. The method is applied to synthetic data sets as well as to data collected by ANTARES.


The IceCube Collaboration has submitted a paper «Search for High-Energy Neutrinos from Ultra-Luminous Infrared Galaxies with IceCube» to Astrophysics Journal and posted it at [2107.03149] (

The runs with synthetic data reveal that one can reliably model the emitted bioluminescent flashes of the organisms. Furthermore, it is found that the spatial resolution of the localization of light sources highly depends on the configuration of the telescope. Precise measurements of the efficiencies of the detectors and the attenuation length of the water are crucial to reconstruct the light emission. Finally, the application to ANTARES data reveals the first precise localizations of bioluminescent organisms using neutrino telescope data.

Ultra-luminous infrared galaxies (ULIRGs) have infrared luminosities LIR > 1012 LSun making them the most luminous objects in the infrared sky. They are generally powered by starbursts with star-formation rates that exceed 100 MSun yr-1, possibly combined with a contribution from an active galactic nucleus.  Such environments make ULIRGs plausible sources of astrophysical high-energy neutrinos. 

The paper presents a stacking search for high-energy neutrinos from a representative sample of 75 ULIRGs with redshift z < 0.13 using 7.5 years of IceCube data (see next figure). 




The results are consistent with a background-only observation, yielding upper limits on the neutrino flux from these 75 ULIRGs. For an unbroken E-2.5 power-law spectrum, an upper 90% C.L. limit on the stacked muon neutrino flux of 3.24 × 10-14 TeV-1 cm-2 s-1 sr-1 (E/10 TeV)-2.5  is derived, see next figure.



Integral limits at 90% confidence level on the contribution of the ULIRG population up to a redshift zmax = 4.0 to the observed diffuse muon-neutrino flux, shown for three unbroken power-law spectra. The limits are plotted within their respective 90% central energy ranges.


Also, the contribution of the ULIRG source population to the observed diffuse astrophysical neutrino flux as well as model predictions is constrained.


gnn00004.jpgPrediction by He et al. (2013) of a diffuse neutrino flux from hypernovae in ULIRGs (full magenta line) and the E-2.0 upper limit at 90% confidence level of this search (dashed blue line). For comparison, a ULIRG source evolution is assumed and integrated up to a redshift zmax = 2.3. The model prediction is in tension with the obtained limit



Prediction by Palladino et al. (2019) of a diffuse neutrino flux, normalized to the IceCube observations, from hadronically powered gamma-ray galaxies (HAGS; full magenta line) and the E-2.12 upper limit at 90% confidence level of this search (dashed blue line). For comparison, a source evolution according to the star-formation rate is assumed and integrated up to a redshift zmax = 4.0. The obtained limit excludes ULIRGs as the sole HAGS that can explain the diffuse neutrino observations.



The IceCube and IceCube-Gen2 collaborations have bundled their papers which can now be found at

[2107.06966] The IceCube Collaboration -- Contributions to the 37th International Cosmic Ray Conference (ICRC2021) (


[2107.06968] The IceCube-Gen2 Collaboration -- Contributions to the 37th International Cosmic Ray Conference (ICRC2021) (

ANTARES, KM3NeT, Baikal-GVD and P-ONE have posted papers individually.

For overviews of our field, see the rapporteur talks of Anna Nelles (“Neutrinos and Muons” at

and of Irene Tamborra (“Multimessenger Astronomy”) at

You have to be a registered participant to get access. Anna’s talk is also freely available at

ICRC Prizes: 

Carlos Arguelles (Harvard) and Francesca Calore (LAPTH, CNRS) won the IUPAP Young scientist awards and Ke Fang (UW Madison) the Shakti P. Duggal Award. The O’Ceallaigh medal was awarded to Paolo Lipari (Univ. Rome and INFN), the Yodh Prize to Antony Bell (Oxford University) and the Bhabha medal to Francis Halzen (UW Madison). Congratulations to the winners! 


Giorgos Androulakis, QA/QC Manager of the KM3NeT Collaboration since 2017, passed away suddenly on the 9th of July 2021, aged 43. 




Read the obituary written by Paschal Coyle, posted also on the KM3NeT website:

Giorgos joined KM3NeT in 2014 as a member of the NCSR “Demokritos” in Athens, Greece and from the start he became deeply involved with the construction of the detectors. In 2017, he took over as the QA/QC Manager of the Collaboration, coordinating the activities for quality control during detector construction and operation and managing a team of local quality supervisors at the institutes involved in the detector construction. He was a key long-term member of the KM3NeT Management Team and the Steering Committee.

Giorgos was unfailing in his help to the institutes when setting up their facilities for the detector construction, to help understand the origin of problems when they arose, and to support people with the intricacies of the database. On the management side, his careful following of non-conformities and probing questions would often lead us to an understanding and a solution for the issue of the day. His logical approach, insight and sage advice were invaluable for many important decisions.

The recent successes of the collaboration in the construction of the seafloor infrastructures and detection units owe so much to his skills, dedication and hard work.

Giorgos was greatly appreciated by all the members of the collaboration; he was the oil that kept us all moving smoothly in the right direction. Many of us mourn a good friend. Personally, I will certainly miss our discussions over a few beers after a hard day at the Collaboration meeting and especially his unique and ironic sense of humor.

On behalf of the KM3NeT Collaboration, I would like to express our sincere condolences to his family and friends at this difficult time.

We will miss him dearly.