Following the light:Novel event reconstruction techniques for neutrino oscillation analyses in KM3NeT/ORCA

Neutrinos are tiny, subatomic particles which currently present some outstanding questions in the field of particle physics. Though neutrino oscillations are now an understood phenomenon, efforts are still underway to measure the neutrino oscillation parameters even more precisely. Furthermore, the ordering of the three neutrino mass states relative to one another - the neutrino mass ordering - is still unknown. The KM3NeT/ORCA detector is currently being built in the Mediterranean Sea to address such questions. This infrastructure surrounds huge volumes of seawater with photodetectors, bypassing the tiny interaction cross section of these particles, and detecting the Cherenkov radiation of products of neutrino interactions in the water. In this thesis, the software used to simulate atmospheric muons in the detector using parametric formulae is tuned to KM3NeT/ORCA data, resulting in an improved simulation of the atmospheric muons, which form the main background for neutrino analyses. A novel neutrino event reconstruction algorithm is developed and explored in this thesis, aiming to reconstruct neutrino events with both a track-like and particle shower-like component. The estimate of the reconstructed neutrino energy is improved upon with this technique, as well as directly reconstructing the fractional energy transfer to the hadronic shower component of the interaction. This reconstruction technique also shows the potential for identifying different neutrino interaction channels. The improved energy estimate and the potential to identify the interaction channel pave the way for future analyses, leading to an improved measurement of the neutrino oscillation parameters and determination of the yet-unknown neutrino mass ordering

Search of Dark Matter Annihilation in the Galactic Centre using the ANTARES Neutrino Telescope

A search for high-energy neutrinos coming from the direction of the GalacticCentre is performed using the data recorded by the ANTARES neutrino telescopefrom 2007 to 2012. The event selection criteria are chosen to maximise thesensitivity to possible signals produced by the self-annihilation of weaklyinteracting massive particles accumulated around the centre of the Milky Waywith respect to the atmospheric background. After data unblinding, the numberof neutrinos observed in the line of sight of the Galactic Centre is found tobe compatible with background expectations. The 90% C.L. upper limits in termsof the neutrino+anti-neutrino flux, $\rm \Phi_{\nu_{\mu}+\bar{\nu}_\mu}$, andthe velocity averaged annihilation cross-section, $\rm$, arederived for the WIMP self-annihilation channels into \rmb\bar{b},W^{+}W^{-},\tau^{+}\tau^{-},\mu^{+}\mu^{-},\nu\bar{\nu}. The ANTARESlimits for $\rm$ are shown to be the most stringent for aneutrino telescope over the WIMP masses $\rm 25\,GeV < M_{WIMP} < 10\,TeV$

Search for exotic neutrino sources with the KM3NeT telescope

The neutrino represents the ideal astronomical messenger. Neutrinos travel large distances without absorption and with no deflection by magnetic fields. Having a very small mass and no electric charge, the neutrino is similar to the photon as an astronomical messenger, except for the fact that it interacts on weakly with the matter. For this reason, high energy neutrinos may reach us unscathed from cosmic distances revealing the proprieties of their sources. On the other hand, their weak interactions also make cosmic neutrinos very difficult to detect. In 1960, Markov suggested to detect high energy neutrinos using huge volumes of transparent natural material such as ice or water. High energy astrophysical neutrinos would weakly interact with one of the nucleons of the medium producing charged particle that emit Cherenkov photons which can be detected by a lattice of photomultipliers. The charged produced particles have almost the same direction of the generating neutrino and this allows to point back to the neutrino sources if the muon direction can be precisely reconstructed. The low cross section of the neutrino interactions and the very low predicted astrophysical neutrino flows suggest that these Cherenkov detectors should be very large, on the scale of km3. The ANTARES neutrino telescope, a three dimensional array of photomultipliers distributed over 12 lines, installed in the Mediterranean was completed in May 2008. It is taking data continuously since then. The main goal of the telescope is the search for high energy neutrinos from astrophysical sources. Its position in the Northern hemisphere and the possibility to look at the Galactic Centre has made it especially useful since it is complementary to the IceCube Antarctic telescope. This complementary view can provide a different insight in the cosmic signal observed only by the IceCube Collaboration. The encouraging results obtained by ANTARES and IceCube during their data taking, the importance of synergy between neutrino telescopes in two different hemispheres and the advent of the multimessenger era have suggested the design of a new generation telescope in the northern hemisphere. The new telescope has to be larger than its predecessor ANTARES but must exploit all the experience acquired during the years of ANTARES operations. This new generation telescope, KM3NeT is under construction and will become the largest telescope for neutrinos in the World. In this thesis, we studied the contribution of a combined analysis of of Icecube and ANTARES data in order to exclude the scenario for which the neutrinos detected by the two telescopes derive from a single power-law model. The possibility of detecting the presence of neutrinos generated from the decay of Dark Matter particles with the new generation KM3NeT telescope was then investigated. The last analysis requires the development of a very detailed Montecarlo code for which the potential of the simulation code currently used by the ANTARES and KM3NeT collaborations has been increased integrating the GENHEN code with the tauonic neutrino regeneration process. Since the "eyes" through which the new generation KM3NeT telescope would scrutinize the presence of neutrinos "beyond the single power law" are the PMTs, we perform and complete characterization of the aforesaids in order to measure their characteristics. This will allow to improve the analysis and to correctly simulate their response in the Montecarlo code

Contributions of KM3NeT to ICRC2023

This document collects the contributions of the KM3NeT collaboration to the ICRC2023 conference, held from July 26 to August 3, 2023, in Nagoya, Japan. KM3NeT submitted 38 contributions to ICRC2023, on neutrino- and multimessenger astronomy, neutrino oscillation physics, cosmic ray physics, searches for dark matter and exotics, calibration, technical detector descriptions, and art. Proceedings are published in Proceedings of Science.Comment: 306 pages, many figures. Collection of proceedings contributions to ICRC2023, published in PoS(ICRC2023), https://pos.sissa.it/444

The Antares Collaboration : Contributions to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague)

The ANTARES detector, completed in 2008, is the largest neutrino telescope in the Northern hemisphere. Located at a depth of 2.5 km in the Mediterranean Sea, 40 km off the Toulon shore, its main goal is the search for astrophysical high energy neutrinos. In this paper we collect the 21 contributions of the ANTARES collaboration to the 34th International Cosmic Ray Conference (ICRC 2015). The scientific output is very rich and the contributions included in these proceedings cover the main physics results, ranging from steady point sources, diffuse searches, multi-messenger analyses to exotic physics

Searches for neutrino counterparts of gravitational waves from the LIGO/Virgo third observing run with KM3NeT

The KM3NeT neutrino telescope is currently being deployed at two different sites in the Mediterranean Sea. First searches for astrophysical neutrinos have been performed using data taken with the partial detector configuration already in operation. The paper presents the results of two independent searches for neutrinos from compact binary mergers detected during the third observing run of the LIGO and Virgo gravitational wave interferometers. The first search looks for a global increase in the detector counting rates that could be associated with inverse beta decay events generated by MeV-scale electron anti-neutrinos. The second one focuses on upgoing track-like events mainly induced by muon (anti-)neutrinos in the GeV–TeV energy range. Both searches yield no significant excess for the sources in the gravitational wave catalogs. For each source, upper limits on the neutrino flux and on the total energy emitted in neutrinos in the respective energy ranges have been set. Stacking analyses of binary black hole mergers and neutron star-black hole mergers have also been performed to constrain the characteristic neutrino emission from these categories.Grants PID2021-124591NB-C41, -C42, -C43 funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union” or by the “European Union NextGenerationEU/PRTR”Programa de Planes Complementarios I+D+I (refs. ASFAE/2022/023, ASFAE/2022/014)Programa Prometeo (PROMETEO/2020/019) and GenT (refs. CIDEGENT/2018/034, /2019/043, /2020/049. /2021/23) of the Generalitat ValencianaJunta de Andalucía (ref. SOMM17/6104/UGR, P18-FR-5057)MSC program (ref. 101025085)Programa María Zambrano (Spanish Ministry of Universities, funded by the European Union, NextGenerationEU)The European Union’s Horizon 2020 Research and Innovation Programme (ChETEC-INFRA — Project no. 101008324)Francqui foundatio

Acoustics for underwater neutrino telescopes

En esta tesis se tratan diferentes aspectos de la acústica presente en un telescopio submarino de neutrinos, principalmente en dos vertientes: en el sistema de posicionamiento acústico utilizado para la monitorización de las posiciones de los módulos ópticos presentes a lo largo del detector, así como en sistemas para detección acústica de neutrinos, técnica que actualmente está en fase de estudio. Todos los estudios realizados están enmarcados dentro de dos colaboraciones europeas para el diseño, construcción y operación de telescopios submarinos de neutrinos: Antares (en fase de operación) y KM3NET (en fase de diseño). Objetivos. Los objetivos de este trabajo pueden resumirse en los siguientes aspectos: - Estudios y análisis del sistema de posicionamiento acústico de Antares. Desarrollo del software para la para la automatización del procesado de los datos de dicho sistema e incorporación de los resultados en la base de datos del experimento. Análisis de los datos proporcionados por dicho sistema con el fin de validar su correcto funcionamiento. - Diseño y desarrollo del sistema de posicionamiento acústico para KM3NeT, telescopio unas 20 veces más grande que Antares. - Estudios para la evaluación de la generación acústica paramétrica para el desarrollo de un calibrador compacto capaz de generar señales tipo neutrino útiles en sistemas de detección acústica. Elementos de la metodología a destacar. Cabe destacar aquí que el trabajo se ha desarrollado en el marco de dos colaboraciones internacionales: ANTARES y KM3NeT, financiados con fondos europeos y nacionales. Por su contexto y el carácter de las actividades realizadas ha sido necesaria la formación en distintos campos: telescopios de neutrinos y astropartículas, pero también en otras áreas como la acústica submarina. Además, se ha desarrollado diversas capacidades y destrezas en diversos ámbitos: en instrumentación, en aplicaciones informáticas, en análisis de datos, etc. Más concretamente, se ha trabajado en aplicaciones informáticas para los desarrollos y análisis en ANTARES.Bou Cabo, M. (2011). Acoustics for underwater neutrino telescopes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/10989Palanci

Event reconstruction for KM3NeT/ORCA using convolutional neural networks

The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches