Follow-up of multi-messenger alerts with the KM3NeT ARCA and ORCA detectors

The strength of multi-messenger astronomy comes from its capability to increase the significance of a detection through the combined observation of events coincident in space and time. This is particularly valuable for transient events, since the use of a narrow time window can allow a reduction of background of the search. In KM3NeT, we are actively monitoring and analysing a variety of external triggers in real-time, including alerts like IceCube neutrinos, HAWC gamma-ray transients, LIGO-Virgo- KAGRA gravitational waves, SNEWS neutrino alerts, and others. In this contribution, we present the follow-up of various external alerts using the comple- mentary capabilities of the two KM3NeT detectors, ORCA (covering the few GeV to few TeV energy range) and ARCA (ranging from sub-TeV energies up to tens of PeV). Both detectors were collecting high-quality data with partial configurations during the period of the studied alerts, which goes from December 2021 until June 2023

The Power Board of the KM3NeT Digital Optical Module: design, upgrade, and production

The KM3NeT Collaboration is building an underwater neutrino observatory at the bottom of the Mediterranean Sea consisting of two neutrino telescopes, both composed of a three-dimensional array of light detectors, known as digital optical modules. Each digital optical module contains a set of 31 three inch photomultiplier tubes distributed over the surface of a 0.44 m diameter pressure-resistant glass sphere. The module includes also calibration instruments and electronics for power, readout and data acquisition. The power board was developed to supply power to all the elements of the digital optical module. The design of the power board began in 2013, and several prototypes were produced and tested. After an exhaustive validation process in various laboratories within the KM3NeT Collaboration, a mass production batch began, resulting in the construction of over 1200 power boards so far. These boards were integrated in the digital optical modules that have already been produced and deployed, 828 until October 2023. In 2017, an upgrade of the power board, to increase reliability and efficiency, was initiated. After the validation of a pre-production series, a production batch of 800 upgraded boards is currently underway. This paper describes the design, architecture, upgrade, validation, and production of the power board, including the reliability studies and tests conducted to ensure the safe operation at the bottom of the Mediterranean Sea throughout the observatory's lifespa

Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope

[EN] The ANTARES detector is an undersea neutrino telescope in the Mediterranean Sea. The search for pointlike neutrino sources is one of the main goals of the ANTARES telescope, requiring a reliable method to evaluate the detector angular resolution and pointing accuracy. This work describes the study of the Sun ¿shadow¿ effect with the ANTARES detector. The shadow is the deficit in the atmospheric muon flux in the direction of the Sun caused by the absorption of the primary cosmic rays. This analysis is based on the data collected between 2008 and 2017 by the ANTARES telescope. The observed statistical significance of the Sun shadow detection is 3.7¿, with an estimated angular resolution of 0.59° +- 0.10°for downward-going muons. The pointing accuracy is found to be consistent with the expectations and no evidence of systematic pointing shifts is observed.The authors acknowledge the financial support of the funding agencies: Centre National de la Recherche Scientifique, Commissariat `a l'' energie atomique et aux energies alternatives, Commission Europeenne (FEDER fund and Marie Curie Program), Institut Universitaire de France, LabEx UnivEarthS (ANR-10-LABX-0023 and ANR-18-IDEX-0001), R ' egion Ile-de-France (DIM-ACAV), Region Alsace (contract CPER), Region Provence-Alpes-Cote d'Azur, Departement du Var and Ville de La Seyne-sur-Mer, France; Bundesministerium fur Bildung und Forschung, Germany; Istituto Nazionale di Fisica Nucleare, Italy; Nederlandse organisatie voor Wetenschappelijk Onderzoek, the Netherlands; Council of the President of the Russian Federation for Young Scientists and Leading Scientific Schools supporting grants, Russia; Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), Romania; Ministerio de Ciencia, Innovacion, Investigacion y Universidades (MCIU): Programa Estatal de Generacion de Conocimiento (refs. PGC2018-096663-B-C41, -A-C42, -B-C43, -B-C44) (MCIU/FEDER), Severo Ochoa Centre of Excellence and MultiDark Consolider (MCIU), Junta de Andalucia (refs. SOMM17/6104/UGR and A-FQM-053-UGR18), Generalitat Valenciana: Grisolia (ref. GRISOLIA/2018/119), Spain; Ministry of Higher Education, Scientific Research and Professional Training, Morocco. We also acknowledge the technical support of Ifremer, AIM and Foselev Marine for the sea operation and the CC-IN2P3 for the computing facilities.Albert, A.; Andre, M.; Anghinolfi, M.; Anton, G.; Ardid Ramírez, M.; Aubert, J.; Aublin, J.... (2020). Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope. Physical Review D: covering particles, fields, gravitation, and cosmology. 102(12):1-7. https://doi.org/10.1103/PhysRevD.102.122007S1710212Ageron, M., Aguilar, J. A., Al Samarai, I., Albert, A., Ameli, F., André, M., … Ardid, M. (2011). ANTARES: The first undersea neutrino telescope. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 656(1), 11-38. doi:10.1016/j.nima.2011.06.103Alexandreas, D. E., Allen, R. C., Berley, D., Biller, S. D., Burman, R. L., Cady, D. R., … Zhang, W. (1991). Observation of shadowing of ultrahigh-energy cosmic rays by the Moon and the Sun. Physical Review D, 43(5), 1735-1738. doi:10.1103/physrevd.43.1735Andreyev, Y. M., Zakidyshev, V. N., Karpov, S. N., & Khodov, V. N. (2002). Cosmic Research, 40(6), 559-564. doi:10.1023/a:1021553713199Borione, A., Catanese, M., Covault, C. E., Cronin, J. W., Fick, B. E., Gibbs, K. G., … van der Velde, J. C. (1994). Observation of the shadows of the Moon and Sun using 100 TeV cosmic rays. Physical Review D, 49(3), 1171-1177. doi:10.1103/physrevd.49.1171Cobb, J. H., Marshak, M. L., Allison, W. W. M., Alner, G. J., Ayres, D. S., Barrett, W. L., … Wall, D. (2000). Observation of a shadow of the Moon in the underground muon flux in the Soudan 2 detector. Physical Review D, 61(9). doi:10.1103/physrevd.61.092002Bartoli, B., Bernardini, P., Bi, X. J., Bleve, C., Bolognino, I., Branchini, P., … Cao, Z. (2012). Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector. Physical Review D, 85(2). doi:10.1103/physrevd.85.022002Abeysekara, A. U., Albert, A., Alfaro, R., Alvarez, C., Álvarez, J. D., Arceo, R., … Belmont-Moreno, E. (2018). Constraining the p¯/p ratio in TeV cosmic rays with observations of the Moon shadow by HAWC. Physical Review D, 97(10). doi:10.1103/physrevd.97.102005Adamson, P., Andreopoulos, C., Ayres, D. S., Backhouse, C., Barr, G., Barrett, W. L., … Bock, G. J. (2011). Observation in the MINOS far detector of the shadowing of cosmic rays by the sun and moon. Astroparticle Physics, 34(6), 457-466. doi:10.1016/j.astropartphys.2010.10.010Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., … Ansseau, I. (2019). Detection of the Temporal Variation of the Sun’s Cosmic Ray Shadow with the IceCube Detector. The Astrophysical Journal, 872(2), 133. doi:10.3847/1538-4357/aaffd1Albert, A., André, M., Anghinolfi, M., Anton, G., Ardid, M., Aubert, J.-J., … Barrios-Martít, J. (2018). The cosmic ray shadow of the Moon observed with the ANTARES neutrino telescope. The European Physical Journal C, 78(12). doi:10.1140/epjc/s10052-018-6451-3First search for neutrinos in correlation with gamma-ray bursts with the ANTARES neutrino telescope. (2013). Journal of Cosmology and Astroparticle Physics, 2013(03), 006-006. doi:10.1088/1475-7516/2013/03/006Aguilar, J. A., Al Samarai, I., Albert, A., André, M., Anghinolfi, M., Anton, G., … Astraatmadja, T. (2011). A fast algorithm for muon track reconstruction and its application to the ANTARES neutrino telescope. Astroparticle Physics, 34(9), 652-662. doi:10.1016/j.astropartphys.2011.01.003BECHERINI, Y., MARGIOTTA, A., SIOLI, M., & SPURIO, M. (2006). A parameterisation of single and multiple muons in the deep water or ice. Astroparticle Physics, 25(1), 1-13. doi:10.1016/j.astropartphys.2005.10.005Carminati, G., Bazzotti, M., Margiotta, A., & Spurio, M. (2008). Atmospheric MUons from PArametric formulas: a fast GEnerator for neutrino telescopes (MUPAGE). Computer Physics Communications, 179(12), 915-923. doi:10.1016/j.cpc.2008.07.014Yepes-Ramírez, H. (2013). Characterization of optical properties of the site of the ANTARES neutrino telescope. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 725, 203-206. doi:10.1016/j.nima.2012.11.143Fusco, L. A., & Margiotta, A. (2016). The Run-by-Run Monte Carlo simulation for the ANTARES experiment. EPJ Web of Conferences, 116, 02002. doi:10.1051/epjconf/201611602002Albert, A., André, M., Anghinolfi, M., Anton, G., Ardid, M., Aubert, J.-J., … Basa, S. (2017). First all-flavor neutrino pointlike source search with the ANTARES neutrino telescope. Physical Review D, 96(8). doi:10.1103/physrevd.96.082001Albert, A., André, M., Anghinolfi, M., Anton, G., Ardid, M., Aubert, J.-J., … Belhorma, B. (2020). ANTARES and IceCube Combined Search for Neutrino Point-like and Extended Sources in the Southern Sky. The Astrophysical Journal, 892(2), 92. doi:10.3847/1538-4357/ab7afbAdrián-Martínez, S., Albert, A., André, M., Anghinolfi, M., Anton, G., Ardid, M., … Basa, S. (2014). SEARCHES FOR POINT-LIKE AND EXTENDED NEUTRINO SOURCES CLOSE TO THE GALACTIC CENTER USING THE ANTARES NEUTRINO TELESCOPE. The Astrophysical Journal, 786(1), L5. doi:10.1088/2041-8205/786/1/l

The Control Unit of the KM3NeT Data Acquisition System

The KM3NeT Collaboration runs a multi-site neutrino observatory in the Mediterranean Sea. Water Cherenkov particle detectors, deep in the sea and far off the coasts of France and Italy, are already taking data while incremental construction progresses. Data Acquisition Control software is operating off-shore detectors as well as testing and qualification stations for their components. The software, named Control Unit, is highly modular. It can undergo upgrades and reconfiguration with the acquisition running. Interplay with the central database of the Collaboration is obtained in a way that allows for data taking even if Internet links fail. In order to simplify the management of computing resources in the long term, and to cope with possible hardware failures of one or more computers, the KM3NeT Control Unit software features a custom dynamic resource provisioning and failover technology, which is especially important for ensuring continuity in case of rare transient events in multi-messenger astronomy. The software architecture relies on ubiquitous tools and broadly adopted technologies and has been successfully tested on several operating systems

KM3NeT broadcast optical data transport system

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

Embedded Software of the KM3NeT Central Logic Board

The KM3NeT Collaboration is building and operating two deep sea neutrino telescopes at the bottom of the Mediterranean Sea. The telescopes consist of latices of photomultiplier tubes housed in pressure-resistant glass spheres, called digital optical modules and arranged in vertical detection units. The two main scientific goals are the determination of the neutrino mass ordering and the discovery and observation of high-energy neutrino sources in the Universe. Neutrinos are detected via the Cherenkov light, which is induced by charged particles originated in neutrino interactions. The photomultiplier tubes convert the Cherenkov light into electrical signals that are acquired and timestamped by the acquisition electronics. Each optical module houses the acquisition electronics for collecting and timestamping the photomultiplier signals with one nanosecond accuracy. Once finished, the two telescopes will have installed more than six thousand optical acquisition nodes, completing one of the more complex networks in the world in terms of operation and synchronization. The embedded software running in the acquisition nodes has been designed to provide a framework that will operate with different hardware versions and functionalities. The hardware will not be accessible once in operation, which complicates the embedded software architecture. The embedded software provides a set of tools to facilitate remote manageability of the deployed hardware, including safe reconfiguration of the firmware. This paper presents the architecture and the techniques, methods and implementation of the embedded software running in the acquisition nodes of the KM3NeT neutrino telescopes

Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling

KM3NeT is a research infrastructure being installed in the deep Mediterranean Sea. It will house a neutrino telescope comprising hundreds of networked moorings — detection units or strings — equipped with optical instrumentation to detect the Cherenkov radiation generated by charged particles from neutrino-induced collisions in its vicinity. In comparison to moorings typically used for oceanography, several key features of the KM3NeT string are different: the instrumentation is contained in transparent and thus unprotected glass spheres; two thin Dyneema® ropes are used as strength members; and a thin delicate backbone tube with fibre-optics and copper wires for data and power transmission, respectively, runs along the full length of the mooring. Also, compared to other neutrino telescopes such as ANTARES in the Mediterranean Sea and GVD in Lake Baikal, the KM3NeT strings are more slender to minimise the amount of material used for support of the optical sensors. Moreover, the rate of deploying a large number of strings in a period of a few years is unprecedented. For all these reasons, for the installation of the KM3NeT strings, a custom-made, fast deployment method was designed. Despite the length of several hundreds of metres, the slim design of the string allows it to be compacted into a small, re-usable spherical launching vehicle instead of deploying the mooring weight down from a surface vessel. After being lowered to the seafloor, the string unfurls to its full length with the buoyant launching vehicle rolling along the two ropes. The design of the vehicle, the loading with a string, and its underwater self-unrolling are detailed in this paper.French National Research Agency (ANR) ANR-15-CE31-0020Centre National de la Recherche Scientifique (CNRS)European Union (EU)Institut Universitaire de France (IUF)LabEx UnivEarthS ANR-10-LABX-0023 ANR-18-IDEX-0001Paris Ile-de-France Region, FranceShota Rustaveli National Science Foundation of Georgia (SRNSFG), Georgia FR-18-1268German Research Foundation (DFG)Greek Ministry of Development-GSRTIstituto Nazionale di Fisica Nucleare (INFN), Ministero dell'Universita e della Ricerca (MUR), PRIN Italy NAT-NET 2017W4HA7SMinistry of Higher Education, Scientific Research and Professional Training, MoroccoNetherlands Organization for Scientific Research (NWO) Netherlands GovernmentNational Science Center, Poland National Science Centre, Poland 2015/18/E/ST2/00758National Authority for Scientific Research (ANCS), RomaniaMinisterio de Ciencia, Innovación, Investigación y Universidades (MCIU): Programa Estatal de Generación de Conocimiento (MCIU/FEDER) PGC2018-096663-B-C41 PGC2018-096663-B-A-C42 PGC2018-096663-B-BC43 PGC2018-096663-B-B-C44Severo Ochoa Centre of Excellence and MultiDark Consolider (MCIU), Junta de Andalucía SOMM17/6104/UGRGeneralitat Valenciana GRISOLIA/2018/119 CIDEGENT/2018/034La Caixa Foundation LCF/BQ/IN17/11620019EU: MSC program, Spain 71367

Dependence of atmospheric muon flux on seawater depth measured with the first KM3NeT detection units: The KM3NeT Collaboration

KM3NeT is a research infrastructure located in the Mediterranean Sea, that will consist of two deep-sea Cherenkov neutrino detectors. With one detector (ARCA), the KM3NeT Collaboration aims at identifying and studying TeV–PeV astrophysical neutrino sources. With the other detector (ORCA), the neutrino mass ordering will be determined by studying GeV-scale atmospheric neutrino oscillations. The first KM3NeT detection units were deployed at the Italian and French sites between 2015 and 2017. In this paper, a description of the detector is presented, together with a summary of the procedures used to calibrate the detector in-situ. Finally, the measurement of the atmospheric muon flux between 2232–3386 m seawater depth is obtained

Prospects for combined analyses of hadronic emission from γ\gamma-ray sources in the Milky Way with CTA and KM3NeT

The Cherenkov Telescope Array and the KM3NeT neutrino telescopes are major upcoming facilities in the fields of $\gamma$-ray and neutrino astronomy, respectively. Possible simultaneous production of $\gamma$ rays and neutrinos in astrophysical accelerators of cosmic-ray nuclei motivates a combination of their data. We assess the potential of a combined analysis of CTA and KM3NeT data to determine the contribution of hadronic emission processes in known Galactic $\gamma$-ray emitters, comparing this result to the cases of two separate analyses. In doing so, we demonstrate the capability of Gammapy, an open-source software package for the analysis of $\gamma$-ray data, to also process data from neutrino telescopes. For a selection of prototypical $\gamma$-ray sources within our Galaxy, we obtain models for primary proton and electron spectra in the hadronic and leptonic emission scenario, respectively, by fitting published $\gamma$-ray spectra. Using these models and instrument response functions for both detectors, we employ the Gammapy package to generate pseudo data sets, where we assume 200 hours of CTA observations and 10 years of KM3NeT detector operation. We then apply a three-dimensional binned likelihood analysis to these data sets, separately for each instrument and jointly for both. We find that the largest benefit of the combined analysis lies in the possibility of a consistent modelling of the $\gamma$-ray and neutrino emission. Assuming a purely leptonic scenario as input, we obtain, for the most favourable source, an average expected 68% credible interval that constrains the contribution of hadronic processes to the observed $\gamma$-ray emission to below 15%.Comment: 18 pages, 15 figures. Submitted to journa