Teses / dissertações: "Neutrinoless double-Beta decays"

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Lobasenko, Andrii. "The neutrino nature through the study of the Xenon 136 double-beta decays on the PandaX-III experiment". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP051.

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La recherche de la désintégration double bêta sans neutrino (0νββ) est cruciale pour faire progresser notre compréhension de la physique et explorer la physique au-delà du modèle standard. Cependant, cette recherche est incroyablement difficile en raison de l'extrême rareté de la désintégration, qui nécessite une interprétation approfondie et une dépendance aux contraintes expérimentales et aux modèles nucléaires théoriques. L'expérience PandaX-III est dédiée à la recherche de 0νββ dans 136-Xe. Il s'agit d'une chambre de projection temporelle (TPC) gazeuse à haute pression équipée de détecteurs Micromegas. Ce choix a été fait pour maximiser la capacité de détection des traces de particules et minimiser les fluctuations statistiques dans la résolution énergétique. L'un des principaux défis de la recherche d'événements 0νββ est la discrimination entre le signal et les événements de bruit de fond, qui contaminent la région d'intérêt (ROI). Le système de lecture par pistes des détecteurs Micromegas (une combinaison de 52 détecteurs forme un plan de lecture) permet la reconstruction 2D précise des trajectoires d'ionisation avec les informations de charge et de temps. Cela permet d'étudier l'énergie et la topologie des trajectoires d'électrons et, en conséquence, de distinguer le signal du bruit de fond. Pour supprimer la scintillation et ne se baser que sur le signal d'ionisation, le 136-Xe gazeux enrichi à 90% est mélangé avec 1% de triméthylamine (TMA) qui joue le rôle de "quencher". La résolution énergétique actuelle de l'expérience PandaX-III est de 3% pour l'énergie de 2457 keV de la désintégration de 136-Xe 0νββ, et devrait être améliorée à 1%. Cependant, plusieurs facteurs peuvent dégrader la résolution en énergie, tels que la présence de canaux morts, les inhomogénéités de gain dans les détecteurs Micromegas ou l'attachement des électrons dans la TPC. Ce travail de doctorat présente une étude de l'impact des canaux manquants sur les reconstructions d'énergie et de topologie dans l'expérience PandaX-III. Les résultats de la détermination de la charge du blob n'offrent pas la possibilité souhaitée de reconstituer la partie de son énergie qui aurait été perdue en raison des canaux manquants dans XZ à partir des projections YZ des traces d'événements reconstruites et vice versa. Cependant, l'étude a montré qu'il est possible d'utiliser des algorithmes d'apprentissage automatique pour atténuer l'impact des canaux manquants sur ls reconstruction de l'énergie et de la topologie. Un modèle de réseau neuronal convolutif (CNN) a été développé pour prédire l'énergie réelle des électrons à partir des données simulées collectées par les Micromegas avec des canaux manquants. Les résultats finaux montrent que le modèle CNN prédit l'énergie réelle des événements enregistrés par les Micromegas avec des canaux manquants avec une grande efficacité. Nous observons une amélioration de l'efficacité de détection du signal de Monte Carlo dans la ROI, qui passe de 69% à 89% après l'application du modèle CNN, par rapport à l'approche directe consistant à additionner les amplitudes des signaux provenant des Micromegas dont les canaux sont manquants. Un autre modèle CNN a également été utilisé pour classer les événements à deux électrons des événements à un seul électron dans les données de Monte Carlo affectées par des canaux manquants. Le modèle est capable de rejeter 99% des événements de bruit de fond tout en conservant une efficacité de 26% pour les signaux 0νββ dans la ROI. Les résultats de ce travail sont prometteurs et ouvrent la voie à d'autres études visant à améliorer la résolution en énergie et le rejet du bruit de fond dans l'expérience PandaX-III
The search for neutrinoless double-beta decay (0νββ) is crucial for advancing our understanding of physics and exploring physics beyond the Standard Model. However, this pursuit is incredibly challenging due to the decay's extreme rarity, requiring profound interpretation and reliance on experimental constraints and theoretical nuclear models. The PandaX-III experiment is dedicated to the search for 0νββ in 136-Xe. It is a high-pressure gaseous Time Projection Chamber (TPC) with Micromegas detectors. This design choice is made to maximize the particle track detection and discrimination 0νββ signal vs. gamma background capabilities. One of the main challenges of the 0νββ search is the discrimination between the signal and background events, which contaminate the region of interest (ROI). The strip readout system of the Micromegas detectors (a combination of 52 of them form a readout plane) allows for the precise 2D reconstruction of the ionization tracks together with the charge and time information. This allows for studying the electron tracks' energy and topology and ultimately discriminating the signal from the background. To suppress the scintillation light and rely only on the ionization signal, a 90% enriched 136-Xe is mixed with a 1% trimethylamine (TMA) quencher. The current energy resolution of the PandaX-III experiment is 3% for the 2457 keV energy of the 136-Xe 0νββ decay, envisioned to be improved to 1%. However, several factors can degrade the energy resolution, such as the presence of dead channels, gain inhomogeneities in the Micromegas detectors, or electron attachment in the TPC. This Ph.D work presents a study on the impact of missing channels on the energy and topology reconstructions in the PandaX-III experiment. The results of the Blob charge determination do not provide the desired possibility of reconstituting the part of the blob energy that would have been lost due to missing channels in XZ from YZ projections of reconstructed event tracks and vice versa. However, the study gave insight into employing machine learning (ML) algorithms to mitigate the impact of missing channels on energy and topology reconstructions. A Convolutional Neural Network (CNN) model was developed to predict the true energy of the electrons from the simulated data collected by the Micromegas with missing channels. The final results show that the CNN model predicts the true energy of the events recorded by the Micromegas with missing channels with a good energy resolution. We observe an improvement in the detection efficiency of the Monte Carlo 0νββ signal in the ROI from 69% to 89% after applying the CNN model, in comparison to the direct approach of directly summing amplitudes of the signals from the Micromegas with missing channels. Another CNN model was also used to classify the two-electron events from the single-electron events in the Monte Carlo data affected by missing channels. The model is capable of rejecting 99% of the background events while maintaining a 26% efficiency for the 0νββ signal in the ROI. The results of this work are promising and pave the way for further studies to improve the energy resolution and background rejection in the PandaX-III experiment

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CARRETTONI, MARCO ANDREA. "Data analysis for neutrinoless double beta decay". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/20134.

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Double Beta Decay (ββ) is a rare transition between two isobars, involving the change of the nuclear charge Z by two units. In Nature we have several even- even nuclei for which this is the only allowed decay mode. Several theoretical speculations point toward a mass generation mechanism that imply a Majorana character of neutrinos and that indicates in the 0ν-DBD process the unique tool with a discovery potential.This thesis is subdivided in two parts: the first three chapters should give an idea of the CUORICINO, from its theoretical context up to the evaluation of the 0ν-DBD limit, while the last chapters are a description of my contributions to the analysis of this experiments.

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MAGANA, VSEVOLODOVNA RUSLAN IDELFONSO. "Transfer reactions, neutrinoless double beta decay and double charge exchange". Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/930766.

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Pascoli, Silvia. "Elementary Particle Physics Aspects of Neutrinoless Double Beta-Decay". Doctoral thesis, SISSA, 2002. http://hdl.handle.net/20.500.11767/4261.

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Jones, Philip G. "Background rejection for the neutrinoless double beta decay experiment SNO+". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:e99b0c4a-2cce-4e0a-9ce1-e0b8de12b264.

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The SNO+ experiment will use a liquid scintillator based detector to study solar, geo, and reactor neutrinos and double beta decay. This thesis discusses the effect of backgrounds on the measurement of neutrinoless double beta decay and describes analysis techniques developed to reduce their impact. Details of the modeling of the photomultiplier tubes in the SNO+ Monte Carlo RAT are first described and comparisons are made with the SNO Monte Carlo SNOMAN. SNOMAN has been extensively verified with calibration sources and RAT is shown to be in good agreement. The event reconstruction techniques are then presented and predict an achievable 15cm position and 7% energy resolution. The backgrounds are discussed and pileup backgrounds identified, including many previous unknown pileup backgrounds. Techniques to reject the pileup background are presented and shown to give over 99% rejection in the region of the double beta decay end point (3-4MeV), below the irreducible background from solar neutrinos. Finally the resulting limit on the effective Majorana neutrino mass SNO+ could achieve in 2015 is predicted to be 270meV and this is compared with other experiments that are underway.

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Sparks, Larua Christine. "Contributing efforts in the search for neutrinoless double beta decay /". Click here to view, 2009. http://digitalcommons.calpoly.edu/physsp/1/.

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Gehman, Victor M. "Physics reach of the global neutrinoless double-beta decay program and systematic uncertainties of the Majorana project /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9695.

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Back, Ashley Robert. "Probing new physics mechanisms in neutrinoless double-beta decay with SNO+". Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/33945.

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In this thesis, I present the theory of neutrinoless double-beta decay (0 2 ), particularly the theory of exotic modes of 0 2 involving the emission of one or two Majorons. Alongside this, I summarise the most recent results in the experimental search for 0 2 , including limits on the rate of these exotic processes. I describe the SNO+ experiment and it's physics goals, which include the search for 0 2 . As part of the SNO+ collaboration, I have made a signi cant contribution towards the development of the data quality software that is essential for ensuring SNO+ can achieve its physics goals-including in 0 2 searches. I describe how I developed a software package that performs the high-level data quality checks. Continuing with the software theme, I then describe a python-based limit-setting and tting software package called echidna. I have been a lead developer of echidna as part of my PhD, so I describe the software in detail and how it can be used to set limits on 0 2 signals. By reproducing the sensitivity results of the KamLAND-Zen experiment, in four key Majoronemitting 0 2 modes, I verify the use of echidna as a limit-setting tool for this type of search. Finally, I present the results of a comprehensive sensitivity study, where I determine the potential sensitivity of SNO+ to the same set of Majoron-emitting modes that KamLAND-Zen and other 0 2 experiments have already investigated.

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Monge, Camacho Henry Jose. "Lattice Qcd for Neutrinoless Double Beta Decay: Short Range Operator Contributions". W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153991.

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The Standard Model (SM), the fundamental theory of particle physics, very success- fully describes the world around us, and with a only a few tantalizing exceptions, all the experiments we have performed to understand the fundamental laws of nature. However, the SM accounts for only 4-5% of the matter and energy in the universe, with approxi- mately 25% composed of dark matter (DM) and the remaining 70% composed of the more mysterious dark energy. Further, the SM content of the universe is composed of an excess of matter over anti-matter of about 1 part per billion. Despite being a small excess, it is orders of magnitude larger than can be explained by the SM alone. These observations strongly suggest there is new physics Beyond the Standard Model (BSM). One of the most exciting prospects for searching for physics BSM is 0νββ. Detecting 0νββ is one of the current top scientific priorities of The Nuclear Science Advisory Committee and a new initiative, a ton-scale 0νββ experiment, is described in their Long Range Plan for Nuclear Science [1]. There are many experiments designed world wide to search for evidence of physics BSM, however, the ton-scale search for 0νββ in large nuclei is the most prominent new nuclear physics (NP) experiment. 0νββ, if allowed, is an extremely rare nuclear decay, which violates one of the fundamental symmetries of the Standard Model (SM). There- fore, if observed, 0νββ may provide a possible explanation for the observed abundance of matter over anti-matter in the universe as this lepton number violation could be converted to baryon number violation very early in the universe. 0νββ would happen in a process where two neutrons decay simultaneously into two protons and two electrons but without the emission of any neutrinos. If the neutrinos are their own antiparticles (Majorana-like), the most plausible case, a neutrino emitted from one of the beta-decaying neutrons can be absorbed by the other neutron. This interaction would happen at short distance scales. Thus, a series of calculations based on Quantum ChromoDynamics (QCD), the fundamen- tal theory of nuclear strong interactions, will be required to interpret the results of 0νββ experiments, along with many other NP experiments. However, the only way to perform such calculations to the required accuracy is by using a numerical technique known as lattice QCD (LQCD).

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Waterfield, James. "Optical calibration system for SNO+ and sensitivity to neutrinoless double-beta decay". Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/67570/.

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The SNO+ experiment is primarily looking for neutrinoless double-beta decay, an unobserved, lepton number violating radioactive decay. This is achieved by loading liquid scintillator with tellurium whose isotope 130Te decays via double beta decay with a Q-value of 2527 keV. An optical calibration system, located outside the scintillator, has been developed to help meet the radiopurity requirements of the experiment. This thesis describes the hardware component of the optical calibration system which calibrates the timing and charge response of the photomultiplier tube array of SNO+. A set of quality assurance tests showed that the system was at the required standard for installation. Data taken with SNO+ and the optical calibration system showed that the system was stable enough for photomultiplier tube calibration, identified resolvable issues with the SNO+ data acquisition system and allowed measurement of single photoelectron spectra. Data quality checks have been developed to ensure data is of calibration standard. The sensitivity of SNO+ to neutrinoless double-beta decay with nearly 800 kg of 130Te and five years data taking is investigated with a comprehensive evaluation of systematic uncertainties. Two new methods for acquiring a greater sensitivity to neutrinoless double-beta decay were developed; a one dimensional fit in event energy and a multidimensional fit in event energy and position. A simple event counting analysis, developed previously by the collaboration, was shown to be sensitive to systematic uncertainties. A fit in an extended energy range was shown to constrain the systematics and achieve a half-life sensitivity of 9.30x1025 yr corresponding to a 5.6% improvement over the counting analysis which neglected systematic uncertainties. The multidimensional analysis with systematics included achieved a 20% improvement over the counting analysis with a half-life sensitivity of 1:06 x 1026 yr, corresponding to an effective Majorana mass between 52 to 125 meV.

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POZZI, STEFANO. "Search for double-beta decay of 130Te to the excited states of 130Xe in CUORE-0". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/158137.

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CUORE-0 è stato un esperimento bolometrico, mantenuto in funzione dal 2013 al 2015, il cui scopo scientifico principale è stata la ricerca del decadimento doppio beta senza emissione di neutrini (0vbb) nel 130Te. Il rivelatore era costituito da 52 cristalli di TeO2, usati sia come rivelatore che come sorgente dell'isotopo di interesse. I cristalli erano organizzati in una singola torre e contenuti in un criostato capace di raggiungere la temperatura di 10 mK. Grazie al basso fondo radioattivo raggiunto dall'esperimento, la ricerca di altri processi rari, oltre al decadimento doppio beta senza emissione di neutrini, è stata possibile. In questa tesi descrivo i metodi che ho usato per la ricerca del decadimento doppio beta del 130Te sugli stati eccitati del 130Xe. Questo decadimento è caratterizzato dall'emissione di due elettroni, seguiti da una cascata di fotoni, dandogli una segnatura chiaramente identificabile. Ho studiato due processi distinti, il decadimento con l'emissione di due neutrino, permesso dal Modello Standard, e il decadimento senza emissione di neutrini. Per poter identificare chiaramente la segnatura di questi decadimenti è stato necessario ottimizzare una procedura di analisi dedicata, che ha richiesto l'uso sia di dati reali che simulati. I due decadimenti non sono stati osservati in CUORE-0, ma è stato possibile dare un limite inferiore al relativo tempo di dimezzamento: per il decadimento senza emissione di neutrini T1/2 > 5.44x10^23 anni, mentre per il decadimento con l'emissione di due neutrini T1/2 > 1.85x10^23 anni. In particolare, il risultato per il canale con l'emissione di due neutrini rappresenta un netto miglioramento rispetto al limite preesistente, determinato dall'esperimento Cuoricino e pari a 1.30x10^23 anni. La combinazione dei risultati di CUORE-0 e Cuoricino permette di raggiungere limiti ancora migliori: T1/2 > 1.48x10^24 anni per il decadimento senza neutrini e T1/2 > 2.19x10^23 anni per il decadimento con due neutrini. Questi risultati rappresentano i limiti più stringenti disponibili al momento per entrambi i processi.
CUORE-0 was a bolometric experiment, operated between 2013 and 2015, whose main scientific goal was the search for neutrinoless double-beta decay (0vbb) in 130Te. The detector consisted of 52 TeO2 crystals, used both as a detector and a source for the isotope under investigation. The crystals were arranged in a single tower and contained in a cryostat capable of reaching the temperature of 10 mK. Thanks to the low background of the experiment, searches for rare events other than 0vbb are possible. In this thesis I describe the methods used to search for double-beta decay of 130Te on the excited states of 130Xe. This decay is characterized by the emission of two electrons followed by a photon cascade, giving it a very characteristic signature. I studied two distinct processes, the SM-allowed two neutrino double-beta decay and neutrinoless double-beta decay on the excited states. In order to properly detect the signatures of these decays a dedicated optimization of the analysis procedure, involving both real and simulated data, was required. The two decays are not observed in CUORE-0, but a lower limit on the half-life of both processes can be set: for the neutrinoless decay, T1/2 > 5.44x10^23 yr, and for the two neutrino decay T1/2 > 1.85x10^23. The result from the two neutrino channel from CUORE-0 was a clear improvement over the previously existing half-life limit, set by the Cuoricino experiment at 1.30x#10^23 years. The combination of the results from CUORE-0 and Cuoricino yields even better limits: T1/2 > 1.48x10^24 years for the neutrinoless channel and T1/2 > 2.19x10^23 for the two neutrino channel. These results represent the most stringent limits currently available for both processes.

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Zolotarova, Anastasiia. "Study and selection of scintillating crystals for the bolometric search for neutrinoless double beta decay". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS293/document.

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L'observation de la désintégration double bêta sans émission de neutrino (0ν2β) fournirait des informations essentielles sur la nature du neutrino et son échelle de masse absolue. Ce processus consiste en la transformation simultanée de deux protons en deux neutrons avec l'émission de deux électrons et aucun neutrino. Cette transition n'est possible que si les neutrinos sont égaux aux antineutrinos (nature Majorana du neutrino). Les recherches pour une désintégration à ce point rare représentent un défi technique complexe, car les expériences de prochaine génération visent des sensibilités de l'ordre de 10^27-10^28 ans afin d'avoir un potentiel de découverte élevé. Cette thèse est focalisée sur les projets LUMINEU et CUPID-Mo, développant la technique des bolomètres scintillants pour la recherche de désintégration 0ν2β avec le radio-isotope 100Mo.Les bolomètres sont des détecteurs cryogéniques mesurant l'énergie des particules déposées via un changement de température dans l'absorbeur. Si des cristaux scintillants sont utilisés comme absorbeurs, les signaux lumineux peuvent être enregistrés avec un bolomètre auxiliaire, sensible à l'énergie totale déposée par les photons de scintillation. Une telle configuration permet de séparer les particules α des γ/β, en rejetant le fond le plus difficile. La technologie des bolomètres scintillants est décrite en détail comme une option pour une future expérience cryogénique à l'échelle d'une tonne, appelée CUPID, qui peut couvrir complètement la région de masses de neutrinos dans la hiérarchie inversée
Neutrinoless double beta (0ν2β) decay is a process of great interest for neutrino physics: its observation would provide essential information on neutrino nature and its absolute mass scale. This process consists of the simultaneous transformation of two protons into two neutrons with the emission of two electrons and no neutrino, implying the violation of the total lepton number. Such transition is possible only if neutrinos are equal to antineutrinos (Majorana particles). The searches for such a rare decay are becoming a complicated technical challenge, as next generation of 0ν2β experiments aim at sensitivities of the order of half-life at 10^27-10^28 yr. This thesis is focused on LUMINEU and CUPID-Mo projects, developing the scintillating bolometers technique for 0ν2β decay search with 100Mo with Li2MoO4 crystals. Bolometers are cryogenic detectors measuring the deposited particle energy as a change of temperature in the absorber. The use of scintillating crystals allows to perform discrimination of α particles from γ/β ones due to different light output of these two particle types, rejecting the most challenging background. The scintillating bolometers technology is described in details as an option for a future ton-scale cryogenic experiment, named CUPID, which can completely cover the inverted hierarchy region of neutrino masses

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Pattavina, Luca. "Radon-induced surface contaminations in neutrinoless double beta decay and dark matter experiments". Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00640789.

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In experiments looking for rare events, like neutrinoless double beta decay (DBD0v) and dark matter search (DM), one of the main issues is to increase the experimental sensitivity through the material selection and production. In the specific the background contribution coming from the materials used for the detector realization has to be minimized. Moreover the net reduction of the background produced by the bulk part of the apparatus has raised concerns about the background contribution coming from the surfaces. Many procedures and techniques were developed during the last years in order to remove and to minimize the presence of possible contaminants on detector surfaces. To succeed in this strategy a big effort was put in defining all possible mechanisms that lead to surface contaminations, as well as specific cleaning procedures, which are able to reduce and control the surface radioactivity. The presence in air and gases of possible radioactive elements that can stick on the detector surfaces can lead to a recontamination process that will vanish all the applied cleaning procedures. Here is presented and analyzed the contribution to the background of rare events experiments like CUORE (DBD0v) and EDELWEISS (DM) produced by an exposure of their detector components to a big activity of 222Rn, radioactive daughter isotope from the 238U chain.

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Tenconi, Margherita. "Development of luminescent bolometers and light detectors for neutrinoless double beta decay search". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112224/document.

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L'étude de la double désintégration bêta sans neutrinos joue un rôle important dans plusieurs questions en physique des particules et cosmologie. Ce processus nucléaire hypothétique viole la conservation du nombre leptonique par deux unités et jusqu'à présent il est le seule moyen pratique pour dévoiler la nature du neutrino : sa détection implique forcement que neutrino et antineutrino sont la même particule. En outre, le taux de décroissance est sensible à la masse efficace de Majorana du neutrino, du coup à l'échelle absolue des valeurs propres de la masse et leur hiérarchie. La marque expérimentale de la DDB0ν est un pic monochromatique dans le spectre énergétique de la somme des deux électrons émis. Le but des expériences de prochaine génération est une sensibilité sur la masse efficace du neutrino de l'ordre de dizaines de meV, c'est-à-dire demi-vies de l'ordre de 10²⁷-10²⁸ années : en pratique, il s'agit de construire des sources de quelques centaines de kg d'isotope candidat, au moins, et les sonder par des détecteurs très efficients, tout en gardant le bruit de fond dans la région énergétique d'intérêt au niveau d'un coup/tonne/an. Les bolomètres luminescents sont une technique prometteuse vu leur excellentes résolutions énergétiques, haute efficacité de détection, ample choix pour les matériaux et extensibilité modulaire à grande échelle; de plus, grâce à la détection simultanée de chaleur et lumière produites par l'interaction des particules, il est possible de discriminer les contaminations α, dangereuse source de bruit aux énergies d'intérêt pour plusieurs noyaux candidats à la DDB0ν. Cette thèse a été effectuée dans le contexte de l'expérience LUMINEU : une expérience pilote qui a pour but la construction d'une expérience de prochaine génération basée sur les bolomètres scintillants en molybdate de zinc, pour l'étude de l'isotope candidat ¹⁰⁰Mo. En vue de la construction d'une expérience à grande échelle, il est nécessaire d'effectuer des caractérisations systématiques pour s'assurer des performances et de la reproductibilité des détecteurs et leurs composantes. La disponibilité d'installations expérimentales en surface, facilement accessibles, est souhaitable pour des tests routiniers : j'ai mené la plupart des expériences au CSNSM, où j'ai aussi travaillé à l'installation d'un nouvel cryostat à dilution basé sur la technologie du Pulse-Tube. Une partie de ma thèse a concerné l'étude de détecteurs bolométriques de lumière aux absorbeurs en germanium et thermomètres NTD (thermistors Neutron Transmutation Doped) : une structure standard pour LUMINEU a été établie et on a mesuré les performances des bolomètres telles que sensibilité, résolution énergétique, bruit de base et reproductibilité. Les résultats sont satisfaisants en vue d'un emploi dans une expérience avec bolomètres scintillants, bien que la configuration soit très sensible à la microphonie. En outre, j'ai testé avec succès des détecteurs bolométriques de lumière exploitants l'effet Neganov-Luke, qui augmente le rapport signal-bruit au niveau compatible avec la détection de la lumière Cherenkov pour la discrimination des événements. Une autre partie a vu la caractérisation des bolomètres scintillants en molybdate de zinc avec masse allant jusqu'à environ 300 g : couplés aux capteurs de lumière susmentionnés et lus par thermistors NTD, ils ont été refroidis en surface au CSNSM et en endroit souterrain à Modane, dans l'installation de l'expérience EDELWEISS pour la Matière Noire. Grâce à la détection simultanée de lumière et chaleur, les interactions des particules β/γ sont séparées des contaminations α. Les résultats démontrent que la caractérisation de bolomètres massifs, presque la taille cible des détecteurs finaux, est possible même en surface, en dépit du rayonnement cosmique. En outre, ces tests ont permis d'optimiser la compatibilité de l'installation de Modane avec les exigences des bolomètres scintillants pour la recherche de la DDB0ν
Neutrinoless Double Beta Decay (0νDBD) is regarded as an important key in the decryption of some hot astroparticle and cosmological enigmas: it violates lepton number by two units and it is currently the only known practical way to shed light on the neutrino nature, being possible only in case of a Majorana neutrino, identical to its antiparticle. Moreover, the 0νDBD rate is sensitive to the effective neutrino mass, so it would be useful to define the absolute neutrino mass scale and hierarchy. The experimental footprint of 0νDBD is a monochromatic peak in the sum energy spectrum of the two emitted electrons. Next-generation experiments aim at reaching a sensitivity on the effective neutrino mass of the order of ten meV, corresponding to half lives in the range 10²⁷-10²⁸ years: this means to be able to gather, at least, a few hundred kilograms of 0νDBD candidate isotope source and to efficiently scrutinize it with very sensitive detectors. Meanwhile, background levels in the energy region of interest of the 0νDBD signal should be lowered to less than one count/ton/y. Cryogenic luminescent bolometers are a promising technique for 0νDBD search, as they feature excellent energy resolutions, high detection efficiency, flexibility in the material choice and easy scalability to large modular experiments; furthermore, the simultaneous read-out of heat and light signals produced by particle interactions provides an active discrimination method against the dangerous α contaminations, populating the 0νDBD energy region of several interesting candidate isotopes. The work presented in this dissertation was carried out in the context of the LUMINEU project: a pilot experiment focused on zinc molybdate scintillating bolometers, to define the strategies for the construction of a next-generation experiment based on the 0νDBD candidate ¹⁰⁰Mo. In view of the construction of a large 0νDBD experiment, involving hundreds of modules, systematic cryogenic measurements have to be performed to ensure good performance and reproducibility of the detectors and their components. Aboveground facilities are preferred for routinary tests because of their easier accessibility: most of the tests were carried out at CSNSM, where I also worked on the setup of a new cryogenic apparatus, based on the Pulse-Tube technology. One part of my thesis work saw the study of bolometric light detectors based on germanium absorbers and Neutron Transmutation Doped (NTD) thermometers: a proper design was developed in view of LUMINEU and the devices were characterized in terms of sensitivity, energy resolution, baseline noise and reproducibility. The results are compatible with a 0νDBD search final experiment, though this detector configuration is very sensitive to vibrational noise. In addition, the feasibility of bolometric light detectors based on NTD thermometers and Neganov-Luke amplification was investigated, demonstrating that this technique can actually boost the signal-to-noise gain to a level compatible with event discrimination based on Cherenkov light detection. Another part of my work dealt with the test of scintillating zinc molybdate bolometers of mass up to ~300 g, coupled to the aforementioned light detectors and operated both in the aboveground facilities at CSNSM and underground at Modane, in the cryostat of the EDELWEISS Dark Matter search experiment. Good event discrimination capability was achieved: thanks to double read-out of heat and light, it is possible to identify α particles, the threatening background for 0νDBD interests, against β/γ interactions. The results proved the possibility to pre-characterize aboveground detectors of mass close to the one of a final experiment module, despite the high cosmic rays rates. Besides, the measurements opened the way to the mutual compatibility of the underground setup, conceived for another kind of experiment, and LUMINEU 0νDBD search detectors

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Reeve, Christopher J. "Data analysis and background studies for the Cobra Neutrinoless Double-Beta decay experiment". Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506998.

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PAGNANINI, LORENZO. "Advanced search for neutrinoless double beta decay in selenium-82 with CUPID-0". Doctoral thesis, Gran Sasso Science Institute, 2018. http://hdl.handle.net/20.500.12571/9684.

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The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso (LNGS), is the first large array of enriched scintillating cryogenic detectors for the investigation of 82Se neutrinoless double-beta decay (0⌫). The assembly of the experiment ended in October 2016 and after four months of commissioning, debugging and performance optimization the data taking has started in March 2017. No evidence of signal was found in a 1.83 kg · y 82Se exposure, setting the best lower limit on the 0⌫ 82Se half-life T0⌫ 1/2 >2.4 · 1024 y (90% C.I.), which corresponds to an effective Majorana neutrino mass m < 376-770 meV depending on the nuclear matrix element calculations. The heat-light readout provided a powerful tool for ↵- particles rejection and allowed to suppress the background in the region of interest to (3.6+1.9 1.4) · 103 counts/(keV · kg · y), an unprecedented level for this technique. This result was achieved by a forefront technology for background suppression and thorough protocols and procedures for detector preparation. This Ph.D. work describes all the different phases of the detector design, construction and optimization carried out at LNGS since February 2015. Moreover the analysis tasks such us pulse shape analysis, evaluation of internal contamination and eventually the fit in the region of interest are discussed.

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PATTAVINA, LUCA MARIA. "Radon-induced surface contaminations in neutrinoless double beta decay and dark matter experiments". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/19277.

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In experiments looking for rare events, like neutrinoless double beta decay (DBD0v) and dark matter search (DM), one of the main issue is to increase the experimental sensitivity through the material selection and production. In the specific minimizing the background contribution coming from the materials used for the detector realization. Moreover the net reduction of the background produced by the bulk part of the apparatus has raised concerns about the background contribution coming from the surfaces. Many procedures and techniques were developed during the last years in order to remove and to minimize the presence of possible contaminants on detector surfaces. To succeed in this strategy a big effort was put in defining: all possible mechanisms that lead to surface contaminations, specific cleaning procedures which are able to reduce and control the surface radioactivity. The presence in air and gases of possible radioactive elements that can stick on the detector surfaces can lead to a recontamination process that will vanish all the applied cleaning procedures. It will be presented and analyzed the contribution that an exposure of detector components to 222Rn, a radioactive isotope produced by the 238U chain, rich environment will have on the background of rare events experiments like CUORE (DBD0v) and EDELWEISS (DM).

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Entwisle, Jonathan. "Changes in proton occupancies pertaining to putative neutrinoless double beta decay in 130Te and 136Xe". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/changes-in-proton-occupancies-pertaining-to-putative-neutrinoless-double-beta-decay-in-130te-and-136xe(d4bc9c3c-81a9-49f1-b63a-2abd6c3984fc).html.

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A systematic study of the change in proton single-particle occupancies in two neutrinoless double beta decay candidates, 130Te to 130Xe and 136Xe to 136Ba, has been performed. Final states in 129Sb, 129I, 135I and 135Cs have been populated using the (d,3He) single proton removal reaction. The deuterons were accelerated to 101 MeV using the coupled azimuthally varying field and Ring cyclotrons at the Research Center for Nuclear Physics, University of Osaka. The outgoing ejectiles were momentum analysed using the Grand Raiden magnetic spectrometer. Absolute cross sections were measured for states up to 7 MeV in excitation. Transferred angular momenta were identified through a comparison of angular distributions with those calculated using the distorted-wave Born approximation. Spectroscopic factors were extracted from the experimental cross sections. In addition to the 0v2B decay candidates the reaction was also performed on 128Te, 132Xe, 134Xe and 138Ba as a consistency check. The occupancies of the nuclei were determined from the spectroscopic factors, the reaction model was normalised using a common normalisation factor across all targets. The change in occupancies between the 0v2B decay candidates and their daughters were then determined. The change in occupancies were then compared with those calculated by interacting shell model, interacting boson model and quasiparticle random phase approximation. This comparison showed that whilst the three theories were qualitatively able to reproduce the change in occupancies, quantitatively there are significant discrepancies. These are the same models that are used to determine the nuclear matrix elements governing the rate of 0v2B decay.

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Armatol, Antoine. "Innovative methods for background rejection in next-generation neutrinoless double beta decay bolometric experiments". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP105.

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La recherche de la désintégration double bêta sans émission de neutrino (0ν2β) est un enjeu majeur de la physique contemporaine car son observation démontrerait que le neutrino est une particule de Majorana. La demi-vie du processus étant reliée à la masse effective de Majorana mββ, cela fournirait aussi une mesure de l'échelle de masse du neutrino et une information sur la hiérarchie de masse. L'expérience de prochaine génération CUPID vise à atteindre une sensibilité suffisamment grande pour explorer complètement l'espace des valeurs pour mββ dans le cas de la hiérarchie inversée de masse. Elle utilisera pour cela des bolomètres scintillants constitués d'un cristal de Li₂MoO₄ (LMO), contenant du ¹⁰⁰Mo comme isotope candidat à la 2β, couplé à un détecteur de lumière bolométrique en Ge. Grâce à la méthode de double mesure lumière/chaleur, CUPID va pouvoir rejeter le bruit de fond dû aux particules α qui est la principale source limitant la sensibilité de CUORE, sa prédécesseur, et vise à obtenir un bruit de fond de 10⁻⁴ coups/kg/keV/an (ckky) dans sa région d'intérêt (ROI). Si après CUPID la 0ν2β nous échappe toujours, il faudra pousser la réduction du bruit de fond à un niveau encore meilleur pour maintenant explorer le spectre des valeurs pour mββ possibles seulement dans le cas de la hiérarchie normale de masse. C'est dans ce contexte que s'inscrivent BINGO (Bi-Isotope 0ν2β Next Generation Observatory) et les travaux de cette thèse. Ce projet vise à tester des méthodes innovantes pour atteindre un bruit de fond de 10⁻⁵ ckky dans la ROI du ¹⁰⁰Mo mais aussi du ¹³⁰Te respectivement dans des cristaux de LMO et de TeO₂. Tout d'abord, un assemblage innovant des bolomètres réduisant la quantité de matériel passif autour des détecteurs a été développé et validé. Deuxièmement, une R&D sur l'implémentation d'un veto cryogénique actif composé de scintillateurs autour du volume contenant les bolomètres a été faite pour rejeter les événements γ provenant de l'extérieur par coïncidence. Une étude des potentiels candidats a mené à la sélection du BGO pour le matériel composant le scintillateur. Un test cryogénique d'un module prototype du veto contenant deux BGO est aussi reporté dans cette thèse. D'autres mesures relatives à la collection de lumière ont aussi été réalisées à température ambiante. Finalement, pour utiliser les cristaux de TeO₂ comme bolomètres scintillant, il est nécessaire de booster les performances des détecteurs de lumière. Pour cela, BINGO va utiliser des détecteurs utilisant l'effet de Neganov-Trofimov-Luke (NTL) pour amplifier le signal. Une campagne de R&D a été réalisée pour tester une nouvelle méthode de déposition des électrodes d'aluminium ainsi que différentes géométries pour celles-ci
The search for neutrinoless double beta decay (0ν2β) is a major challenge in contemporary physics, as its observation would demonstrate that the neutrino is a Majorana particle. The half-life of the process being related to the effective Majorana mass mββ, it would also provide a measure of the neutrino mass scale and information on its mass hierarchy. The next-generation experiment CUPID aims to reach a sensitivity high enough to explore completely the region of possible values for mββ in the case of the inverted hierarchy. It will use scintillating bolometers made of a Li₂MoO₄ (LMO) crystal, containing ¹⁰⁰Mo as the 2β candidate isotope, coupled to a Ge bolometric light detector. Thanks to the dual light/heat readout, CUPID will be able to reject the background due to α particles, which is the main source limiting the sensitivity of CUORE, its predecessor, and aims to achieve a background level of 10⁻⁴ counts/kg/keV/year (ckky) in the region of interest (ROI). However, if the 0ν2β still eludes us after CUPID, we will have to push the background reduction even further to explore the spectrum of values for mββ possible in the case of the normal mass hierarchy. It is in this context that BINGO (Bi-Isotope 0ν2β Next Generation Observatory) and the work of this thesis lay. This project aims to test innovative methods for achieving a background of 10⁻⁵ ckky in the ROI of ¹⁰⁰Mo but also of ¹³⁰Te, respectively embedded in LMO and TeO₂ crystals. Firstly, an innovative assembly of bolometers reducing the amount of passive material around the detectors has been developed and validated. Secondly, R&D on implementing a cryogenic active veto composed of scintillators around the volume containing the bolometers was done to reject external γ events by coincidence. A study of potential candidates led to the selection of the BGO for the material. A cryogenic test of a prototype veto module containing two BGOs is also reported in this thesis. Other light collection measurements have also been done at room temperature. Finally, to use TeO₂ crystals as scintillating bolometers, it is necessary to boost the performance of the light detectors. To achieve this goal, BINGO will operate light detectors using the Neganov-Trofimov-Luke (NTL) effect to amplify the signal. An R&D campaign has been conducted to test a new method for depositing aluminum electrodes and different electrode geometries

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Wong, Chan Fai. "Phenomenology of sterile neutrinos at different mass scales : neutrinoless double beta decay and neutrino oscillations". Thesis, Durham University, 2012. http://etheses.dur.ac.uk/4931/.

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The existence of neutrino oscillation is the first evidence of physics beyond the Standard Model. It proves that neutrinos are massive and motivates the study of the neutrino nature, mixings and mass generation models. To have a better understanding of neutrino masses and mixings, the existence and character of sterile neutrinos would be an important factor. In this thesis, we will describe the phenomena of neutrinoless double beta decay and sterile neutrino oscillations. The studies of these two topics will contribute to understanding the properties of sterile neutrinos in the heavy and light mass regime. We first study the neutrinoless double beta decay process to tackle the issue about the nature of neutrino. Establishing the nature of neutrinos, whether they are Dirac or Majorana particles is one of the fundamental questions we need to answer in particle physics, and is related to the conservation of lepton number. Neutrinoless double beta decay is the tool of choice for testing the Majorana nature of neutrinos. However, up to now, this process has not been observed, but a wide experimental effort is taking place worldwide and soon new results will become available. Different mechanisms can induce neutrinoless double beta decay and might interfere with each other, potentially leading to suppressed contributions to the decay rate. This possibility would become of great interest if upcoming neutrino mass measurements from KATRIN and cosmological observations found that neutrino mass is larger than 0.2 eV but no positive signal was observed in neutrinoless double beta decay experiments. We focus on the possible interference between light Majorana neutrino exchange with other mechanisms, such as heavy sterile neutrinos and R-parity violating supersymmetric models. We show that in some cases the use of different nuclei would allow to disentangle the different contributions and allow to test the hypothesis of destructive interference. Finally, we present a model in which such interference can emerge and we discuss the range of parameters which would lead to a significant suppression of the decay rate. Heavy sterile neutrino is involved in the studies of neutrinoless double beta decay and mass generation involve. On the other hand, the effect of light sterile neutrino may be present in the oscillation experiments. To measure the light sterile neutrino mixing, high statistics measurements are necessary. A neutrino factory has been suggested as a powerful tool for studying new physics, for example, sterile neutrinos, exploiting its near detectors. Here, we use the new version of GLoBES to study the potential of a low energy neutrino factory (LENF) in constraining the sterile mixing angles and the mass-square difference. Unlike in conventional long baseline neutrino experiments, the electron neutrino disappearance and appearance channels are also included, since they have been proved helpful in constraining some of the mixing angles. We will explore the dependence of the performance of the LENF depending on different experimental setups, such as the detector type (TASD and LiAr), the energy range, the systematic errors. etc. Moreover, the re-analysis of reactor neutrino experiments suggests the presence of neutrino oscillations due to large sterile neutrino mixing with electron neutrino. We show that, with a near detector, LENF can constrain the sterile parameter values in a very small range and helps us to check the recent Reactor Anomaly.

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Szwec, Stuart V. "Transfer reaction studies of medium mass nuclei-single-particle occupancies and neutrinoless double beta decay". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/transfer-reaction-studies-of-medium-mass-nuclei--singleparticle-occupancies-and-neutrinoless-double-beta-decay(6120c9fe-c85d-42fd-908f-e07e07cccd50).html.

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Two separate investigations are presented, both linked by a common interest in the occupancy of the valence neutron orbitals and their relation to nuclear structure studies. A study of the change in neutron occupancy in the 0Î1⁄22Î2 decay of 136 Xe â 136 Ba has been performed. The neutron occupancies of 136 Ba have been probed us- ing the (p,d) and ( 3 He,Î±) neutron-removal reactions and the (d,p) and (Î±, 3 He) neutron-addition reactions, performed at the Institut Physique Nucl Ìeaire, Orsay. The same reactions have been performed on 134 Ba as an additional consistency check. Spectroscopic factors were extracted through a DWBA analysis and the valence orbital occupancies were extracted using the Macfarlane and French sum rules. The change in neutron occupancy that occurs during 0Î1⁄22Î2 decay was then determined and compared to those calculated by using the interacting shell model and the interacting boson model. The comparison showed that while the various models were able to qualitatively describe the change in occupancy, quantitatively there are significant differences between the models. These are the same models that are used to determine the nuclear matrix elements used in determining the rate of 0Î1⁄22Î2 decay. An additional systematic study of the valence neutron occupancies on the seven even stable tin isotopes is presented. The occupancies were probed in two sets of experiments. The first measurement used the low Q-value (p,d) and (d,p) reactions performed at the Maier-Leibnitz-Laboratory, Munich, to extract spec- troscopic information for low-j orbitals. The second measurement used the high Q-value ( 3 He,Î±) and (Î±, 3 He) reactions at the Institut Physique Nucl Ìeaire, Orsay to extract spectroscopic information for high-j states. Absolute cross sections were determined and the amount transferred angular momenta was identified by comparison of angular distributions to those calculated using a DWBA analysis. The spectroscopic factors were used in conjunction with the Macfarlane-French sum rules to determine the valence neutron occupancies. These measurements not only qualitatively test the robustness of sum rules in transfer reactions but also provide information about the neutron occupancy of 116 Sn and 124 Sn, two nu- clei of relevance to 0Î1⁄22Î2 decay. The measured occupancies of these two isotopes were compared to those obtained from recent theoretical calculations.

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CAMPANI, ALICE. "The search for neutrinoless double beta decay of 130Te and 120Te with the CUORE experiment". Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1042404.

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The discovery of neutrino masses through the observation of oscillations has boosted the importance of neutrinoless double beta decay (0νββ). This rare process is a direct probe of Beyond the Standard Model Physics, since it violates the lepton number by two units. Furthermore, 0νββ allows us to investigate the Dirac/Majorana nature of the neutrino and to get information on the neutrino absolute mass scale and ordering. This thesis work is developed in the framework of the CUORE experiment. CUORE (Cryogenic Underground Observatory for Rare Events) is a tonne-scale bolometric experiment whose main goal is the search for the 0νββ of 130Te. The experiment is currently taking data at the Laboratori Nazionali del Gran Sasso (Italy). In the first part of the thesis, the Physics of interest for CUORE and the experimental aspects are introduced. A general overview of the current knowledge in neutrino physics is presented. 0νββ process is introduced within the particle physics scenario in which the Majorana mass of ordinary neutrinos dominate the decay rate. Then, the experimental challenge the observation of double beta decay represents is discussed. After a general overview of the bolometric technique for rare events search, a general description of the CUORE experiment is outlined. Details on the main components of the CUORE detector are provided, focusing on the stringent requirements in terms of background and noise reduction they must satisfy. Finally, we illustrate the calibration system of the CUORE detector, comparing two alternative approaches employed in terms of compliance with the cryogenic infrastructure and performance. The second part of the thesis focuses on the data processing chain. The most important stages of the low level data analysis include the evaluation of signal amplitude, the energy calibration and the identification of coincident events between the detectors. We present a preliminary analysis of the improvements we obtain in the background reconstruction with the optimum trigger and discuss the performance of the external detector calibration system. Finally, we describe the steps to characterise our detector in terms of efficiency of the selection cuts and energy response function. The core of the thesis focuses on two physical analysis, the search for 0νββ decay of 130Te with a total TeO2 exposure of 372.5 kg · yr, and the search for neutrinoless double emitting electron capture (0νECβ+) decay of 120Te with 355.7 kg · yr TeO2 exposure. The data selection and the fit strategy for the search of 0νββ decay in 130Te are discussed in detail. An interpretation of the final result on the 0νββ decay rate estimate is given, with an overview of the major sources of uncertainty on the final results. Then, we present the analysis of a specific double beta decay mode of 120Te. We start introducing the motivations behind a growing interest for the (neutrinoless) double beta decay modes different from β−β−, where electrons are emitted. Then, we describe the physical process analyzed in this dissertation, pointing out the requirements we set to identify candidate signal events. We discuss our data selection, specifying differences with respect to the 0νββ decay analysis of 130Te and we illustrate the statistical approach. Given the complexity of this analysis a preliminary result on the 120Te rate for 0νECβ+ is presented, and the future developments of this study are also introduced.

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Coulter, Ian T. "Modelling and reconstruction of events in SNO+ related to future searches for lepton and baryon number violation". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:495395b3-bf15-4c9b-851d-c13e7dad8a22.

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SNO+ is a liquid scintillator experiment whose physics goals include measurements of solar neutrinos, reactor anti-neutrinos, geo neutrinos and double beta decay. During an initial water phase, it will also search for invisible modes of nucleon decay. This thesis investigates methods of improving the detector's sensitivity to the baryon and lepton violating processes of neutrinoless double beta decay and invisible nucleon decay. It does this through an improved scintillator model, allowing the sensitivity of the detector with different loading techniques to be evaluated, through a new background rejection technique, capable of increasing the active volume of the detector, and with the development of improved position fitters, achieving resolutions of approximately 10 cm in scintillator and 25 cm in water. The sensitivity of SNO+ to invisible modes of nucleon decay is explored, predicting, after one month of data, a limit of t > 1.38 x 10³⁰ years on the decay of neutrons and of t > 1.57 x 10³⁰ years on the decay of protons.

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Chernyak, Dmitry. "Development of cryogenic low background detector based on enriched zinc molybdate crystal scintillators to search for neutrinoless double beta decay of ¹⁰⁰Mo". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112143/document.

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L’observation de la double désintégration bêta sans neutrinos (0ν2β) impliquerait la violation de la conservation du numéro leptonique, signe d’une nouvelle physique au-delà du Modèle Standard, et permettrait d’établir la nature de Majorana des neutrinos. Les bolomètres scintillants cryogéniques sont parmi les détecteurs les plus prometteurs pour rechercher ce processus nucléaire extrêmement rare dans des noyaux qui sont théoriquement entre les plus favorables.Des scintillateurs de ZnMoO₄ ayant une masse de ∼ 0.3 kg, ainsi que des cristaux de Zn¹⁰⁰ MoO₄ enrichi dans l’isotope ¹⁰⁰Mo, ont été produits pour la première fois en utilisant la technique de Czochralski à faible gradient thermique. Les propriétés optiques et de luminescence des cristaux produits ont été étudiées pour évaluer le progrès de la qualité de la croissance des cristaux. Des tests à basse température avec un scintillateur de 313 g de ZnMoO₄et deux scintillateurs de Zn¹⁰⁰ MoO₄ enrichis ont été réalisées en surface au Centre de Sciences Nucléaires et de Sciences de la Matière. On a aussi mené des mesures à faible fond radioactif avec trois cristaux de ZnMoO₄ naturels et deux détecteurs enrichis, installés dans le setup d’ EDELWEISS au Laboratoire Souterrain de Modane.Pour optimiser la collecte de la lumière dans des bolomètres scintillants cryogénique de ZnMoO₄, nous avons simulé par une méthode Monte Carlo la collecte des photons de scintillation dans un module de détection pour différentes géométries, en utilisant le logiciel GEANT4. La réponse à la désintégration 2ν2β de ¹⁰⁰Mo a été simulée pour des détecteurs enrichis de Zn¹⁰⁰ MoO₄ avec forme et masse différente, avec le but de comprendre la structure des spectres 2ν2β en fonctionne de la forme des cristaux. Nous avons simulé aussi la performance de 48 cristaux de Zn¹⁰⁰ MoO₄ ayant une taille de Ø60 × 40 mm et installés dans le cryostat d’EDELWEISS. La contribution au fond de la contamination radioactive interne des cristaux, l’activation cosmogénique et la contamination radioactive du setup ont été simulées.Tenant compte de la modeste résolution temporelle des bolomètres à basse température, nous avons également étudié la contribution au fond à l'énergie Q₂β déterminé par des coïncidences aléatoires de signaux, en particulier du à la décroissance 2ν2β, qui est l'une des sources de fond les plus dangereuses dans les bolomètres cryogéniques. Des méthodes pour le rejet d’événements coïncidant par hasard ont été développées et comparées. Nous avons également analysé la dépendance de l'efficacité de rejet à l’égard des performances du détecteur cryogénique
Observation of neutrinoless double beta (0ν2β) decay would imply the violation of lepton number conservation and definitely new physics beyond the Standard Model, establishing the Majorana nature of neutrinos. Cryogenic scintillating bolometers look the most promising detectors to search for this extremely rare nuclear process in a few theoretically the most favorable nuclei.ZnMoO₄ scintillators with a mass of ∼ 0.3 kg, as well as Zn¹⁰⁰ MoO₄ crystals enriched in the isotope ¹⁰⁰Mo were produced for the first time by using the low-thermal-gradient Czochralski technique. The optical and luminescent properties of the produced crystals were studied to estimate the progress in crystal growth quality. The low-temperature tests with a 313 g ZnMoO₄ scintillator and two enriched Zn¹⁰⁰ MoO₄ were performed aboveground in the Centre de Sciences Nucléaires et de Sciences de la Matière. The low background measurements with a three ZnMoO₄ and two enriched detectors installed in the EDELWEISS set-up at the Laboratoire Souterrain de Modane were carried out.To optimize the light collection in ZnMoO₄ cryogenic scintillating bolometers, we have simulated the collection of scintillation photons in a detector module for different geometries by Monte Carlo method using the GEANT4 package. Response to the 2ν2β decay of ¹⁰⁰Mo was simulated for the enriched Zn¹⁰⁰ MoO₄ detectors of different shape and mass to understand the dependence of 2ν2β decay spectra on crystal shape. We have simulated 48 Zn¹⁰⁰ MoO₄ crystals with a size of Ø60 × 40 mm installed in the EDELWEISS cryostat. The contribution to background from the internal radioactive contamination of the crystals, cosmogenic activation and radioactive contamination of the set-up were simulated.Taking into account the poor time resolution of the low temperature bolometers, we also studied contribution to background at the Q₂β energy of random coincidences of signals, in particular of 2ν2β decay, which is one of the most valuable sources of background in cryogenic bolometers. Methods of the randomly coinciding events rejection were developed and compared. We have also analyzed dependence of the rejection efficiency on a cryogenic detector performance

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Fatemi-Ghomi, Nasim. "Measurement of the double beta decay half-life of 150Nd and search for neutrinoless decay modes with the NEMO-3 detector". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496229.

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The half-life for two-neutrino double beta decay of ¹⁵⁰Nd has been measured with data taking by the NEMO 3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of ¹⁵⁰Nd the half-life of this process is measured ... this result has significantly improved the previous limit on neutrinoless double beta decay of this isotope. Limits are also set on several other neutrinoless double decay modes.

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Crider, Benjamin P. "Nuclear Structure Relevant to Double-beta Decay: Studies of ⁷⁶Ge and ⁷⁶Se using Inelastic Neutron Scattering". UKnowledge, 2014. http://uknowledge.uky.edu/physastron_etds/17.

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While neutrino oscillations indicate that neutrino flavors mix and that neutrinos have mass, they do not supply information on the absolute mass scale of the three flavors of neutrinos. Currently, the only viable way to determine this mass scale is through the observation of the theoretically predicted process of neutrinoless double-beta decay (0νββ). This yet-to-be-observed decay process is speculated to occur in a handful of nuclei and has predicted half-lives greater than 10²⁵ years. Observation of 0νββ is the goal of several large-scale, multinational efforts and consists of detecting a sharp peak in the summed β energies at the Q-value of the reaction. An exceptional candidate for the observation of 0νββ is ⁷⁶Ge, which offers an excellent combination of capabilities and sensitivities, and two such collaborations, MAJORANA and GERDA, propose tonne-scale experiments that have already begun initial phases using a fraction of the material. The absolute scale of the neutrino masses hinges on a matrix element, which depends on the ground-state wave functions for both the parent (⁷⁶Ge) and daughter (⁷⁶Se) nuclei in the 0νββ decay and can only be calculated from nuclear structure models. Efforts to provide information on the applicability of these models have been undertaken at the University of Kentucky Accelerator Laboratory using gamma-ray spectroscopy following inelastic scattering reactions with monoenergetic, accelerator-produced fast neutrons. Information on new energy levels and transitions, spin and parity assignments, lifetimes, multipole mixing ratios, and transition probabilities have been determined for ⁷⁶Se, the daughter of ⁷⁶Ge 0νββ, up to 3.0 MeV. Additionally, inaccuracies in the accepted level schemes have been addressed. Observation of 0νββ requires precise knowledge of potential contributors to background within the region of interest, i.e., approximately 2039 keV for ⁷⁶Ge. In addition to backgrounds resulting from surrounding materials in the experimental setup, ⁷⁶Ge has a previously observed 3952-keV level with a de-exciting 2040-keV γ ray. This γ ray constitutes a potential background for 0νββ searches, if this level is excited. The cross sections for this level and, subsequently, for the 2040-keV γ ray has been determined in the range from 4 to 5 MeV.

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Gimbal-Zofka, Yann. "Development and study of luminescent bolometers for neutrino physics". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-60660.

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This Master thesis aims at designing, assembling and operating a prototypal luminescentbolometer containing a candidate with high Q-value (116Cd and 100Mo)for the study of the neutrinoless double- decay. The crystal is scintillating (with 116CdWO4 and Li2MoO4 compounds). The prototype is designed according to a simple thermal model and cooled down to 18 mK. Data analysis of the 116CdWO4 crystal determines the energy resolution (intrinsicand in the ROI) and the alpha/beta discrimination power. It includes a full interpretation of the background energy spectrum in terms of environmental radioactivity and an evaluation of the crystal radiopurity by the detection of internal contamination of the detector. An evaluation of the potential of a future experiment based on the 116CdWO4developed prototype is performed, ascertaining the feasibility of large scale experiments to search for neutrinoless double beta decay. The use of the thermal model of the detector response to interpret its bolometric behaviour and the study of future optimizations of the detector performance concludes this project.

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Mcgrath, John. "Research and development of CdZnTe semiconductor detectors in a low background environment for the COBRA neutrinoless double beta decay experiment". Thesis, University of York, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516510.

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Friman-Gayer, Udo [Verfasser], Norbert [Akademischer Betreuer] Pietralla e Wilfried [Akademischer Betreuer] Nörtershäuser. "Probing Nuclear Structure Relevant for Neutrinoless Double-Beta Decay with Nuclear Resonance Fluorescence / Udo Friman-Gayer ; Norbert Pietralla, Wilfried Nörtershäuser". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1203801866/34.

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Mancuso, Michele. "Development and optimization of scintillating bolometers and innovative light detectors for a pilot underground experiment on neutrinoless double beta decay". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS083/document.

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Le travail de doctorat exposé dans ce manuscrit a été développé dans le cadre du projet LUMINEU, une expérience pilote pour la double désintégration bêta sans émission de neutrinos (0νββ) de l'isotope Mo avec des bolomètres scintillants de ZnMoO₄. Ce travail de physique expérimentale implique l'avancement du design et des tests des prototypes de détecteurs, et le développement des outils en vue de la préparation d'une expérience importante. La méthode de détection adoptée dans cette thèse est la technique bolométrique, qui s'intègre bien avec les caractéristiques requises des détecteurs pour étudier les événements rares. Le détecteur fournit une grande efficacité, une très bonne résolution en énergie et il permet la discrimination des particules pour la suppression du fond. Cette thèse se concentre sur la physique du neutrino et sur la désintégration 0νββ; les méthodes de détection expérimentales et la sensibilité de la demi-vie d'une expérience 0νββ sont traitées.La deuxième partie de ce travail est dédiée au setup, l'acquisition et l'analyse des données sont traitées en détails.La dernière partie de la thèse est consacrée aux résultats : les progrès réalisés dans le détecteurs bolométriques et les mesures sont résumés. Sur la base de ces résultats, nous avons calculé une sensibilité finale sur une expérience à venir basée sur ces détecteurs
The current experiments on rare events searches for neutrino and dark matter are at present two of the most relevant and exiting field in particle and astro-particle physics.Thanks to the efforts made in the past years, much of progress has been made in answering some big open questions in this field. In particular, experiments in neutrino physics during the past decades gave very interesting results, stimulating new ideas of the mechanisms beyond the Standard Model. One of them is known as neutrinoless double beta decay which can give important informations on the puzzling picture of how nature behaves. It is a rare nuclear transition with a half life longer than 10^25 years where two neutrons decay simultaneously in to two protons with the emission of only two electrons, the two neutrino acting as a virtual particle between the two decay vertices. This process is possible only if the neutrino is equal to its antiparticle, which is in contrast with the SM predictions.The observation of this phenomenon can determining the nature -- Dirac or Majorana --, of massive neutrinos. This is of fundamental importance for making progress in our understanding of the origin of neutrino masses and mixing and of the symmetries governing the lepton sector of particle interactions. The measurement of the half life of the process would give unvaluable information on the absolute scale of neutrino masses, the Majorana phases and the type ofneutrino mass spectrum.This thesis is deeply related to the LUMINEU project aiming to prepare the construction of a next-generation Neutrinoless Double Beta Decay experiment, capable exploring the inverted hierarchy region of neutrino mass. This goal will be achieved through the development of sophisticated low-temperature detectors named bolometers, which may lead to important advancements in the field of dark matter detection as well.Bolometers are low temperature calorimetric detectors, which can exploit the so called homogeneous approach, which provides very high efficiency. They can be made by almost any dielectric material, giving a flexibility in the source/detector material choice. In addition, their excellent energy resolution makes them very competitive detectors.Scintillating bolometers are upgrade of the simple bolometers, where the absorber can also scintillate. The readout of the scintillating light is made by an auxiliary bolometer and it enables particle identification with the only drawback of doubling the readout channels.In this context, we developed, tested and optimized scintillating bolometers and innovative light detectors for a pilot underground experiment on neutrinoless double beta decay of 100Mo embedded in ZnMoO₄ and Li₂MoO₄ crystal scintillators.We demonstrated that the sensitivity of an experiment searching for neutrinoless double beta decay with scintillating bolometers can compete with reach the present forefront technologies in the field

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Feldmeier, Wolfhart [Verfasser], Peter [Akademischer Betreuer] Fierlinger e Lothar [Akademischer Betreuer] Oberauer. "Search for neutrinoless double beta decay in 136Xe with EXO-200 / Wolfhart Feldmeier. Gutachter: Peter Fierlinger ; Lothar Oberauer. Betreuer: Peter Fierlinger". München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1069127817/34.

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Schütz, Ann-Kathrin [Verfasser], e Peter [Akademischer Betreuer] Grabmayr. "Full analysis of the background for the search of neutrinoless double beta decay in GERDA / Ann-Kathrin Schütz ; Betreuer: Peter Grabmayr". Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1206172932/34.

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Pan, Sheng. "Development of a high pressure xenon gas time projection chamber with a unique cellular readout structure to search for neutrinoless double beta decay". Kyoto University, 2020. http://hdl.handle.net/2433/253472.

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Girardi, Ivan. "Discrete Symmetry Approach to Lepton Flavour, Neutrino Mixing and Leptonic CP Violation, and Neutrino Related Physics Beyond the Standard Theory". Doctoral thesis, SISSA, 2016. http://hdl.handle.net/20.500.11767/4923.

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The experimental evidences of neutrino oscillation, caused by non-zero neutrino masses and neutrino mixing, which were obtained in the experiments with solar, atmospheric, accelerator and reactor neutrinos, opened new field of research in elementary particle physics. The principal goal is to understand at fundamental level the mechanism giving rise to non-zero neutrino masses and neutrino mixing. The open fundamental questions include those of the nature — Dirac or Majorana — of massive neutrinos, of the type of spectrum neutrino masses obey, of the status of CP symmetry in the lepton sector, of the absolute scale of neutrino masses, and more generally, of understanding the origin of flavour in particle physics. The smallness of neutrino masses suggests that their values are related to the existence of a new fundamental mass (energy scale) in particle physics, i.e., to New Physics beyond that predicted by the Standard Theory. The New Physics can manifest itself in the Majorana nature of massive neutrinos, in the existence of sterile neutrinos with masses at the eV scale, in the existence of new non-standard interactions (NSI) of neutrinos, etc. The present Ph.D. thesis explores aspects of this neutrino-related New Physics. More specifically, we first employ the discrete flavour symmetry approach i) to construct a self-consistent theory of lepton flavour, ii) to understand the pattern of neutrino mixing and to describe it quantitatively, and iii) to derive predictions for leptonic Dirac CP violation. Next we investigate the effects of existence of sterile neutrinos with a Majorana mass at the eV scale on the predictions for the neutrinoless double beta decay effective Majorana mass. Further we present a possible interpretation of the results of the reactor neutrino and accelerator experiments (Daya Bay, RENO, Double Chooz and T2K) on the reactor angle θ13 in the neutrino mixing matrix in terms of non-standard interactions (NSI) of neutrinos. We also analyse the signatures of sterile neutrinos in reactor antineutrino experiments and, in particular, constrain the active-sterile mixing angle using the high-precision data of the Daya Bay reactor experiment. We finally investigate the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters in the upcoming neutrino experiment JUNO.

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Kirsch, Andrea [Verfasser], e Werner [Akademischer Betreuer] Hofmann. "Search for the neutrinoless double beta-decay in Gerda Phase I using a Pulse Shape Discrimination technique / Andrea Kirsch ; Betreuer: Werner Hofmann". Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1179925610/34.

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Basharina-Freshville, A. "Search for the neutrinoless double beta decay of 100Mo with the NEMO3 detector and calorimeter research and development for the SuperNEMO experiment". Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1343630/.

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The world’s most precise half-life measurement of T^2nu_1/2 = [7.02 ± 0.01(stat) ± 0.46(syst)] × 10^18 years has been made for the 2\nu\beta\beta decay of ^100Mo using data from 6.9kg collected with the NEMO3 detector over 1471 days. The 2\nu nuclear matrix element has been extracted using T^2nu_1/2 and is M^2\nu = 0.126 ± 0.004. The 0\nu\beta\beta search yielded a limit on the half-life of T^0\nu_1/2 1/1 > 1.1 × 10^24 years at the 90% CL, corresponding to a limit on the effective Majorona mass of \langle M\nu e\rangle < 0.3 - 1.0eV, one of the most stringent constraints on \langle M\nu e\rangle in the world. Limits on the right-handed currents and Majoron 0\nu\beta\beta modes have also been set. The world’s most stringent bound has been set on the Majoron to neutrino coupling constant of \langle g \chi o \rangle < (0.2 − 0.7) × 10^−4. SuperNEMO is a next generation \beta\beta decay experiment, based on the design and experience of NEMO3. Due to start demonstrator operation in 2013, SuperNEMO aims to achieve a sensitivity of 10^26 years, corresponding to \langle M\nu e\rangle < 50-100meV using ^82Se. An alternative to the baseline calorimeter design was considered, using 2m x 10cm x 2.54cm scintillator bars. An energy resolution of 10% FWHM at 1 MeV and a time resolution of ~ 450ps was achieved for the alternative design. This is an unprecedented energy resolution for a scintillator of this size.

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Pompa, Federica. "Neutrino physics with the XENONnT experiment". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19448/.

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One of the most active fields in physics is the search for Dark Matter, for which the XENON Project is one of the main protagonists. The new XENONnT experiment will be operative starting from 2020 in the underground Laboratori Nazionali del Gran Sasso, under 3600 meters water equivalent of mountain rock shield. It is a multi-ton detector for direct search of Dark Matter, consisting of a double phase liquid-gas xenon TPC which contains 5.9 t of liquid xenon target mass, inserted in a Cryostat surrounded by a tank containing 700 t of Gd-loaded water, instrumented with PMTs for muon and neutron tagging. Its aim, as that of its precursor XENON1T, is to detect WIMPs elastic scattering off xenon nucleus through the measure of the light and charge observable signals produced by recoils in LXe. A new neutron Veto system, surrounding the outer Cryostat and instrumented with 120 additional PMTs, will contribute to reduce the neutron background in the TPC. Thanks to the large xenon target used, this experiment is sensitive also to all flavors of Supernova neutrinos. These can be detected through two different interactions channels: through coherent elastic scatters on xenon nuclei in the TPC and through interactions of electron antineutrinos with protons of water via inverse beta decay process. In the first part of this work, after a theoretical introduction to neutrino physics, I present the results of a Monte Carlo simulation to predict the XENONnT detection efficiencies for neutrino events as IBD interactions in the neutron and muon Vetoes. In the last part of the thesis, I investigate the XENONnT possibility to detect neutrinoless double beta decay of Xe-136 isotope, a Standard Model forbidden decay which can prove the Majorana nature of neutrinos. Starting from evaluation of the ER background rate from Cryostat and PMTs in the energy region where we expect to observe neutrinoless double beta decay, the sensitivity of XENONnT for this nuclear decay was estimated.

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Agostini, Matteo [Verfasser], Stefan [Akademischer Betreuer] Schönert e Allen C. [Akademischer Betreuer] Caldwell. "Signal and background studies for the search of neutrinoless double beta decay in GERDA / Matteo Agostini. Gutachter: Stefan Schönert ; Allen C. Caldwell. Betreuer: Stefan Schönert". München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1035502704/34.

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GIRONI, LUCA. "Development of cryogenic detectors for rare event searches". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/20012.

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The experimental evidence of neutrino oscillations clearly showed that the neutrino is a finite-mass particle. Anyway, two big questions concerning the neutrino are still unsolved: its nature (Dirac or Majorana) and the absolute value of its mass. The Double Beta Decay without emission of neutrinos (0nDBD) is at present the most sensitive method to answer the two questions. Bolometers, together with germanium diodes, have provided so far the best results within this kind of research. The choice of the so-called calorimetric approach, where the detector is made of the 0nDBD material, allows the study of large quantities of isotope with an excellent energy resolution (around 0.2-0.3 %). Both features are crucial to disentangle the searched peak from background. The Cuoricino experiment, in which 62 detectors of tellurium dioxide (TeO2) were involved, was carried out in hall A at Laboratori Nazionali del Gran Sasso (LNGS), and represented the bolometric experiment with the best sensitivity concerning the study on the 0nDBD decay. The knowledge achieved in the bolometric technique and its excellent results on 0nDBD led to the development of new experiments to study rare events with bolometric technique. The CUORE (Cryogenic Underground Observatory for Rare Events) experiment, composed by 988 bolometric detectors of TeO2, is under construction and foresees a sensitivity on neutrino mass of the order of about 50 meV. This high sensitivity requires excellent energetic resolutions, low number of spurious counts within the region of interest and high quantity of the 0nDBD active isotope. The reduction of the background in the energetic window where the 0nDBD for the isotope 130Te is expected (Q_bb = 2527 keV) plays a primary role. In this context, the activities I have done are focused primarily on the analysis of the different contributions to the background of CUORE and the optimization of methods for its reduction. This work has been done both through measurements performed in the hall C of LNGS and with Monte Carlo simulations that allowed data interpretation and assessment of the resulting sensitivity. For example, through a series of simulations performed with Geant4 code it is possible to extrapolate the background induced by muons in CUORE. The results of simulations were then validated through the installation of a muon veto above Cuoricino which allowed a direct comparison with experimental measurement. For what concerns the reduction of the bolometers specific background I have also done some measurements for the development, characterization and optimization of some scintillating bolometers. These detectors, thanks to double read-out of thermal and scintillation signals, allow to discriminate different ionizing particles (beta/gamma, alpha and neutrons). This allows a significant reduction of the unwanted background in the region of interest and would therefore allow to approach the condition of `zero background' experiments. Indeed, thanks to the wide choice for the absorber material that allows to study practically all 0nDBD candidate isotopes, it is possible to choose an isotope with a transition energy above 2615 keV and then remove, in practice, all the background due to gamma rays. The 2615 keV gamma line corresponds in fact to the highest energy gamma-ray line from natural radioactivity and is due to 208Tl. Above this energy there are only extremely rare high energy gamma's. Once gamma-rays are no more a worrisome source of background, what is left on the side of radioactivity are alpha emissions. Indeed alpha surface contaminations are already recognized as the most relevant background source in the bolometric experiment Cuoricino. However, thanks to the double read-out of scintillating bolometers, this source of background can be removed too. During my PhD I have tested a number of different crystals and with some of them (CdWO4, ZnSe and some molybdates) I have obtained excellent results both from the point of view of the detector performance and the reduction of the background contributions. Thanks to these results it was possible to evaluate the discrimination power (i.e. the capability to recognize and reject unwanted events) of this technique and extrapolate the sensitivity of a large mass experiment for 0nDBD based on the hybrid heat plus scintillation technique. Moreover, during the analysis of the data collected with the scintillating bolometers, I recognized for the first time, a dependence of the pulse shapes (both on the scintillation and heat channels) on the interacting particle nature. I proposed then to exploit such wonderful feature to discriminate the interacting particles without relying on the much more complicated measurement of both (light and heat) signals. This feature is very promising because it allows to greatly reduce the background in bolometers without getting complicated the assembly of the experiment. In fact in the case of the double read-out of temperature and scintillation both light detectors and reflecting sheet (used to properly collect the scintillation light) are needed in addition to the low temperature calorimeter. Finally, I have proposed a further use of the scintillating bolometer for diagnostic purposes, i.e. the possibility to study surface contaminations with high sensitivity. One of the main limitations in our understanding of the background due to surface contaminations is in fact related to the limited sensitivity of the available standard techniques. Traditionally the devices used in this field are Si surface barrier detectors with an active area of about 10 cm^2, a typical energy resolution of about 25-30 keV FWHM, and counting rates of the order 0.05 count/h/cm^2 between 3 and 8 MeV. A Cuoricino-like bolometer can easily reach a much larger active area (150 cm^2) and, thanks to the absence of a dead layer can reach resolution on surface alpha particles of 10 keV. Moreover a background counting rate in the 3-8 MeV region as low as 0.001 count/h/cm^2 was already reached with this technique. This considerations allow to plan measurements with sensitivities order of magnitude better than standard devices. However, in order to use scintillating bolometer to study surface contaminations, they have not to be surrounded by a reflecting sheet. For these reason it is necessary to use crystals with a very high light yield or crystals that are able to recognize particle from the shape of the thermal pulses (i.e. without any need of collecting the scintillation light). Since this last feature is a very recent discovery and some works have still to be performed before the technique can be considered actually at hand, I have proposed to use a BGO crystal (Bi4Ge3O12), which is characterized by a very high light yield, to study surface contaminations. Preliminary tests with an array of 4 `small' crystals (2x2x2 cm^3) have shown how this possibility could be fulfilled. However this measurement showed a very slow cooling down and an high counting rate due to 207Bi. Therefore, before using the crystal to study surface contamination, a new measurement was carried out with a larger crystal (5x5x5 cm^3). The measurement was successful and showed that the slow cool down and the high counting rate are not intrinsic problems of these crystals. This first test gave excellent results on surface studies and, as supplementary results, a measurement of the rare alpha decay of 209Bi with a high statistical significance was performed.

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PINNA, FEDERICO. "Study and Production of Special Targets for DCE Reactions with 0vbb-Decay Final States in the NUMEN Experiment". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2729322.

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Ziegler, Tobias [Verfasser], Gisela [Akademischer Betreuer] Anton e Gisela [Gutachter] Anton. "Application of Deep Learning Methods to the Search for Neutrinoless Double Beta Decay with the EXO-200 Experiment / Tobias Ziegler ; Gutachter: Gisela Anton ; Betreuer: Gisela Anton". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2020. http://d-nb.info/1217482393/34.

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Becerici, Schmidt Neslihan [Verfasser], Bela [Akademischer Betreuer] Majorovits, Stefan [Akademischer Betreuer] Schönert e Allen C. [Akademischer Betreuer] Caldwell. "Results on Neutrinoless Double Beta Decay Search in GERDA: Background Modeling and Limit Setting / Neslihan Becerici Schmidt. Gutachter: Stefan Schönert ; Allen C. Caldwell ; Béla Majorovits. Betreuer: Béla Majorovits". München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1060193906/34.

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Lazzaro, Andrea [Verfasser], Stefan [Akademischer Betreuer] Schönert, Stefan [Gutachter] Schönert e Susanne [Gutachter] Mertens. "Signal processing and event classification for a background free neutrinoless double beta decay search with the GERDA experiment. / Andrea Lazzaro ; Gutachter: Stefan Schönert, Susanne Mertens ; Betreuer: Stefan Schönert". München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1192911679/34.

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44

Wiesinger, Christoph [Verfasser], Stefan [Akademischer Betreuer] Schönert, Stefan [Gutachter] Schönert e Laura [Gutachter] Fabbietti. "No neutrinos not found : First exploration of neutrinoless double beta decay half-lives beyond 10²⁶ years / Christoph Wiesinger ; Gutachter: Stefan Schönert, Laura Fabbietti ; Betreuer: Stefan Schönert". München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1223617025/34.

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45

Wagner, Victoria Elisabeth [Verfasser], e Manfred [Akademischer Betreuer] Lindner. "Pulse Shape Analysis for the GERDA Experiment to Set a New Limit on the Half-life of Neutrinoless Double Beta Decay of Ge-76 / Victoria Elisabeth Wagner ; Betreuer: Manfred Lindner". Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180739833/34.

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46

Bode, Tobias [Verfasser], Stefan [Akademischer Betreuer] [Gutachter] Schönert e Bela [Gutachter] Majorovits. "The neutrinoless double beta decay experiment GERDA Phase II: A novel ultra-low background contacting technique for germanium detectors and first background data / Tobias Bode ; Gutachter: Stefan Schönert, Béla Majorovits ; Betreuer: Stefan Schönert". München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/111660437X/34.

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47

Loizeau, Johan. "Étude de la stabilité spatiale de XENONnT avec le 83mKr et reconstruction des événements multiples à haute énergie". Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2024. http://www.theses.fr/2024IMTA0411.

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Au sein des interrogations actuelles de la physique contemporaine, celles de la nature de la matière noire et des propriétés des neutrinos comptent parmi les plus importantes. L'observation d'événements rares permettrait alors de répondre à ces questionnements. Avec sa chambre à projection temporelle contenant une cible de xénon liquide de 5,9 tonnes et son très faible bruit de fond, XENONnT se positionne comme un concurrent sérieux dans la recherche des WIMP, une particule candidate de la matière noire. Par son grand volume, le contrôle de la stabilité spatiale du détecteur est indispensable. L'utilisation du Kr83m comme source de calibration interne est adapté à la gamme en énergie des reculs de WIMP et à la dimension de l'instrument. De plus, l'isotope 136 naturellement présent dans le xénon liquide est une source de double désintégration beta. Il permet, en association avec le bruit de fond faible de XENONnT, de participer à la recherche de la désintégration double beta sans émission de neutrino dont l'observation permettrait de déterminer que le neutrino est une particule de Majorana. L'énergie de cette désintégration étant plus grande que celle attendue pour la recherche de matière noire, une méthode de reconstruction spécifique de ces événements à plus haute énergie a dû être développé en utilisant les données de calibration au Th232
Among the current questions of contemporary physics, those of the nature of dark matter and the properties of neutrinos are among the most important. The observation of rare events would then make it possible to answer these questions. With its time projection chamber containing a 5.9-ton liquid xenon target and its very low background noise, XENONnT is a serious competitor in the search for WIMPs, a candidate particle for dark matter. Due to its large volume, the control of the spatial stability of the detector is essential. The use of Kr83m as an internal calibration source is suitable for the WIMP recoil energy range and the instrument size. In addition, the isotope 136 naturally present in liquid xenon is a source of double beta decay. It allows, in association with the low background noise of XENONnT, to participate in the search for neutrinoless double beta decay emission, this observation would allow determining that the neutrino is a Majorana particle. The energy of this decay being larger than the one expected for the dark matter search, a specific reconstruction method for these higher energy events had to be developed using the Th232 calibration data

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48

Meroni, Aurora. "The Nature of Massive Neutrinos and Unified Theories of Flavour". Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4812.

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The present Ph.D. thesis is devoted to two fundamental unsolved problems of neutrino physics, which are intimately connected: determining the nature - Dirac or Majorana - of massive neutrinos, which is related with the possibility of existence of New Physics beyond that predicted by the Standard Model (SM) of particle interactions, and, discovering the origin of the patterns of neutrino masses and of leptonic mixing, stemming from new underlying symmetries in the neutrino, charged lepton and quark sectors. The remarkable experimental efforts of the last 15 years or so have delivered an enormous amount of data that have to be explained in terms of possibly economic and simple theoretical models. Moreover, exciting times are ahead of us. Currently running and future upcoming experiments under construction aim at i) high precision measurement of the parameters characterizing the neutrino oscillations, ii) identifying the neutrino mass hierarchy, and iii) establishing the status of the CP symmetry in the leptonic sector by searching for CP violation effects in neutrino oscillations. In addition, significant experimental efforts are been made to unveil the possible Majorana nature of massive neutrinos by searching for neutrinoless double beta ($\betabeta$-) decay with increasing sensitivity. Unique data on the absolute scale of neutrino masses, which is unknown at present, is expected to be provided by $\beta$-decay experiments under preparation. The first part of the Ph.D. thesis is devoted to the problem of extracting information about the New Physics if it will be experimentally established via the observation of the $\betabeta$-decay that the massive neutrinos are Majorana particles. In this case new couplings, changing the total lepton charge $L=L_e + L_\mu + L_\tau$ by two units, must be admitted in the Lagrangian of particle interactions and there is the possibility that more than one such coupling is operative in $\betabeta$-decay. We discuss four such couplings (arising in seesaw and ight-Left (L-R) symmetric models and in supersymmetric extensions of the SM with $R$-parity nonconservation) and analyze in detail the possibility to determine which couplings, if any, might be involved in $\betabeta$-decay from data on the $\betabeta$-decay half-lives of several different isotopes. In the second part of the Ph.D thesis we analyze the neutrino flavour problem in connection with new underlying symmetries in the leptonic sector. The existence of an organizing principle which could explain the pattern of masses and mixing of the neutrinos is explored in two different approaches based on the use of finite discrete non-Abelian groups. A unified model of flavour based on the symmetry group $SU(5)\times T^\prime$, incorporating the seesaw mechanism of neutrino mass generation is constructed and the predictions of this model for the neutrino mixing angles, the Dirac and Majorana CP violation phases in the neutrino mixing matrix, the sum of neutrino masses and for the $\betabeta$-decay effective Majorana mass are derived. The model can be tested in the future planned neutrino physics experiments.

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Teves, Walter José da Costa. "Estudo fenomenológico dos neutrinos em experimentos que utilizam fontes terrestres". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17072012-125738/.

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Nesta tese, realizamos dois tipos de estudos fenomenológicos através de uma análise detalhada de alguns experimentos terrestres atuais e futuros. No primeiro, estudamos dois mecanismos exóticos de conversão de sabor: descoerência quântica e interações não padrão do neutrino com a matéria. Para descoerência, vinculamos o parâmetro de descoerência bem como testamos como distinguir a solução de descoerência pura do mecanismo padrão de oscilação no contexto de duas gerações. No caso das interações não padrão, assumimos que esta é subdominante frente ao mecanismo de oscilação padrão, e encontramos os possíveis limites que poderão ser obtidos para essas interações utilizando uma fábrica de neutrinos futura. No segundo tipo de estudo, determinamos os parâmetros de oscilação solares pela análise combinada dos dados dos neutrinos solares e de KamLAND, e estimamos a precisão nos parâmetros de mistura atmosféricos que poderá ser atingida pelos experimentos de LongBaseLine futuros MINOS, ICARUS e OPERA. Por fim, investigamos a possibilidade dos experimentos futuros do duplo decaimento sem neutrinos de determinar os parâmetros de não oscilação.
In this thesis, we have done two kind of phenomenological studies through a detailed analysis of present and future terrestrial experiments. In the first study, we analyze two exotic mechanisms of flavour conversion: quantum decoherence and non-standard neutrino-matter interactions. In the case of decoherence, we impose constraints on the decoherence parameter and test how to distinguish between the pure decoherence solution and the standard neutrino ascillation mechanism in the contexto f two neutrino generations. For non-standard interactions, assuming it as a sub-leading process compared to the standard oscillation, we find the possible limits that can be achieved on the strength of these interactions using a future neutrino factory. In the second part of the study, we determine the solar oscillation parameters using a combined analysis of solar neutrino and KamLAND data, and estimate the precision on the atmospheric mixing parameters by that can be accomplished by the LongBaseline experiments MINOS, ICARUS and OPERA. Finally, we investigate the capability of future neutrinoless Double beta decay experiments to determine the non-oscillation parameters.

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Bergström, Johannes. "Predictions of Effective Models in Neutrino Physics". Licentiate thesis, KTH, Teoretisk partikelfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35267.

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Experiments on neutrino oscillations have confirmed that neutrinos have small, but non-zero masses, and that the interacting neutrino states do not have definite masses, but are mixtures of such states.The seesaw models make up a group of popular models describing the small neutrino masses and the corresponding mixing.In these models, new, heavy fields are introduced and the neutrino masses are suppressed by the ratio between the electroweak scale and the large masses of the new fields. Usually, the new fields introduced have masses far above the electroweak scale, outside the reach of any foreseeable experiments, making these versions of seesaw models essentially untestable. However, there are also so-called low-scale seesaw models, where the new particles have masses above the electroweak scale, but within the reach of future experiments, such as the LHC.In quantum field theories, quantum corrections generally introduce an energy-scale dependence on all their parameters, described by the renormalization group equations. In this thesis, the energy-scale dependence of the neutrino parameters in two low-scale seesaw models, the low-scale type I and inverse seesaw models, are considered. Also, the question of whether the neutrinos are Majorana particles, \ie , their own antiparticles, has not been decided experimentally. Future experiments on neutrinoless double beta decay could confirm the Majorana nature of neutrinos. However, there could also be additional contributions to the decay, which are not directly related to neutrino masses. We have investigated the possible future bounds on the strength of such additional contributions to neutrinoless double beta decay, depending on the outcome of ongoing and planned experiments related to neutrino masses.
QC 20110812

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