Nuclear reactors have played an essential role in developing our current understanding of neutrinos. The precision measurement of these high-flux, pure-flavor and controllable artificial neutrino sources shed lights on a wide range of fundamental questions in physics. Specifically, the Reactor Antineutrino Anomaly hints that there may exist a novel eV-scale sterile neutrino, which requires new physics beyond the Standard Model. Performing reactor neutrino spectrum measurements at very-short baseline will improve our imperfect understanding of antineutrino emission from fissile material. CHANDLER is a new-generation neutrino experiment aiming for reactor antineutrino spectrum measurements, to test the eV-scale sterile neutrino oscillation hypothesis unambiguously. The second prototype detector, MiniCHANDLER, was deployed 25 meters from a $2.9~GW_{th}$ commercial nuclear reactor in North Anna, Virginia. To fight against the overwhelming background arising from its surface-level deployment, CHANDLER detectors adopt a novel design using lithium-6 ($^6$Li) loaded zinc sulfide (ZnS) scintillator to tag neutron capture events, which significantly improves the IBD detection efficiency. The use of the Raghavan optical lattice brings enormous enhancement of light collection towards high energy resolution, which unlocks reconstruction of event topology to further suppress backgrounds. The ability of measuring reactor antineutrino spectra enables the potential application of CHANDLER technology in nuclear nonproliferation. This thesis features the prototype detectors instrumentation, data analysis development and Monte Carlo study for the CHANDLER experiment during 2016 to 2020. The detector calibration and energy reconstruction with vertical muon forms a core piece of this thesis. We report our observation of IBD spectrum with 5.5$sigma$ significance with a four month deployment of the minimal shielded MiniCHANDLER prototype at North Anna. The application of separation cuts and topological selections in the analysis are instrumental for a segmented plastic scintillator detector. We also present our results from the proton scintillation quenching measurement at Triangle Universities Nuclear Laboratory, with the deployment of the first prototype detector, MicroCHANDLER, at a neutron beam. / Doctor of Philosophy / The sterile neutrino is a hypothetical particle yet to be observed, whose existence is suggested by a number of physics experiments with strong theoretical motivation. Due to the low chance of a neutrino interacting with matter, most neutrino detectors use a special process called inverse beta decay (IBD) to detect them. The CHANDLER experiment set out to measure antineutrinos produced by a reactor in the vicinity of its core. We found a significant signal of antineutrinos from our four-month deployment. This thesis details the technology and analysis that enables neutrino detection and improves detection efficiency. We also shows how we squeeze out the maximum information available to us from raw data, through the process called reconstruction. Other research topics related to the CHANDLER detector RandD are also included in this thesis.

Over the past 20 years, the detection of neutrino oscillation has reported a lot of important results. The oscillation phenomenon itself has been well proved by various experiments. Some oscillation parameters has been measured and now in the area of precise determination. On the other hand, some new questions like the possibility of the existence of light sterile neutrinos and unexpected 5 MeV bump were raised during the measurement. The Neutrino Lattice Experiment (NuLat) is a detector based on the Raghavan Optical Lattice (ROL). It should be able to offer a compact design of an effective detector with good mobility. It can be extremely useful in the short baseline reactor neutrino oscillation detection community to resolve several confusing issues. In this thesis, we present the calibration results we got from the first active NuLat detector and show what kind of improvements we need for the next version of the NuLat detector based on these results. / Ph. D. / During the last century, physicists have developed a nice framework to describe the physics world we live. The model which we called Standard Model has been constructed to describe the behavior of elementary particles and nicely explain the phenomenon we found from various experiments. However there are still a lot mysteries which cannot be explained by this model and more precise measurements on different fields of particle physics are need to help us improve our understanding about this. Neutrino oscillation is one of the most important field related to this kind of concern. The Neutrino Lattice Experiment (NuLat) is a new type of neutrino detector. It has a good geometry reconstruction ability based on the the Raghavan Optical Lattice (ROL). Since we cannot directly see the elementary particles, we always rely on the signals generated by the reaction between particles and our detector. How to interpret the signals becomes crucial at this point to have high quality experimental data. NuLat is such kind of neutrino detector which offer good ability for us to interpret the signal right. It has a compact design compared to most of other detectors in this field. This is really useful because it can be implemented with limited space where other detectors might have difficulties. Simultaneously the ROL design can help offer nice background rejection ability and high energy resolution. In this thesis, we discuss the progress about develop and assembly of the first active NuLat detector with the preliminary calibration data which give us basic understanding about the performance of this first version.

In dieser Arbeit verwenden wir Flavourinvarianten, um systematisch Lösungen für Probleme des Standardmodells (SM) der Teilchenphysik mit Hilfe verschiedener effektiver Feldtheorien (EFTs) zu untersuchen. In Teil I untersuchen wir die CP-Verletzung im SM und in der SM EFT erweitert mit leichten, sterilen Neutrinos. Wir konstruieren die erzeugende Menge von Flavourinvarianten im νSM, mit der jede Observable als Polynom der Invarianten, sowie die Bedingungen für die CP-Verletzung auf flavourinvariante Weise ausgedrückt werden können. Anschließend weiten wir die Ergebnisse auf die EFT-Wechselwirkungen für verschiedene Szenarien der Neutrinomassen aus. Hier ändert sich die Form der EFT-Flavourinvarianten und ihre Unterdrückung mit der Skala der neuen Physik drastisch mit der untersuchten Art der Neutrinomassen. In Teil II untersuchen wir verschiedene Aspekte der Symmetriebrechung in EFTs von axionartigen Teilchen (ALPs). Wegen ihrer pseudo-Nambu–Goldstone-Natur ist eine wesentliche Eigenschaft der ALPs ihre Shiftsymmetrie (ShS). Wir formulieren flavourinvariante Ordnungsparameter der ShS, die das Powercounting der EFT führender Ordnung bei einer leicht gebrochenen ShS korrekt implementieren lassen. Mit der Hilbertreihe zählen wir die Anzahl der Operatoren, die in der ALP EFT mit und ohne ShS oberhalb und unterhalb der elektroschwachen Skala auftreten, womit wir Operatorbasen konstruieren, die Beziehungen der ShS auf höhere Ordnung verallgemeinern und die CP-verletzenden Flavourinvarianten führender Ordnung konstruieren. Die Axionlösung des starken CP-Problems kann durch neue CP-Verletzung im Ultravioletten durch kleine Instantonen gestört werden. Mit einer SMEFT-Parametrisierung der neuen CP-Verletzung zeigen wir, dass neu konstruierte CP-verletzende SMEFT-Flavourinvarianten explizit in den Instantonberechnungen auftauchen und zur Systematisierung der Berechnungen verwendet werden können, wodurch wir bessere Limits für kleine Instanton- und Flavourszenarien ableiten. / In this thesis, we use flavour invariants to systematically study solutions to problems of the Standard Model (SM) of particle physics with different effective field theories (EFTs). In Part I, we study Charge–Parity (CP) violation in the SM and SM EFT extended with light sterile neutrinos. We construct the generating set of flavour invariants in the νSM allowing us to express any observable as a polynomial of those invariants. In addition, the invariants enable us to express the conditions for CP violation in a flavour-invariant way. We extend the results to the EFT interactions with different scenarios for the neutrino masses. Here, the form of the EFT flavour invariants and their suppression with the scale of new physics changes drastically depending on the nature of the neutrino masses. In Part II, we study different aspects of symmetry breaking in the EFTs of axionlike particles (ALPs). An essential property of ALPs is their shift symmetry (ShS) due to their pseudo-Nambu–Goldstone nature. We formulate flavour-invariant order parameters of ShS, which allow us to properly impose the power counting of the leading order EFT in the presence of a softly broken ShS. Using the Hilbert series, we count the number of operators appearing in the ALP EFT with and without a ShS above and below the electroweak scale. We use this information to construct operator bases, generalise the relations imposing ShS to higher orders and construct the leading order CP-odd flavour invariants. The axion solution to the strong CP problem can be spoiled by new CP violation in the ultraviolet in the presence of small instantons. Parameterising the new CP violation in the SMEFT, we show that newly constructed CP-odd SMEFT flavour invariants, featuring the strong CP angle, explicitly appear in the instanton computations and vice-versa that they can be used to systematise the computations. Using these results, we derive bounds on different small instanton and SMEFT flavour scenarios.

The olive fruit fly, Bactrocera oleae, (Rossi) (Diptera:Tephritidae), is a key pest of olive crops. The sterile insect technique (SIT) is an environmentally benign and species-specific method of pest control, aiming to reduce the reproductive potential of a wild population through the mass-release of sterile insects. Previous olive fly SIT trials, involving the release of gamma-ray sterilised mixed-sex populations, achieved limited success. Key problems included altered diurnal mating rhythms of the laboratory-reared insects, leading to assortative mating between released and wild populations, and low competitiveness of the radiation sterilised mass-reared flies. Consequently, the production of competitive, male-only release cohorts is seen as essential. The RIDL (Release of Insects carrying a Dominant Lethal) system is a transgene-based derivative of SIT, one version of which involves the mass release of insects carrying a female specific lethal transgene (fsRIDL). This thesis describes: 1) the development of fsRIDL olive fly strains and the molecular analysis of transgene insertion and function; 2) the analysis of strain life-history parameters; 3) studies into sexual selection and mating compatibility; 4) a caged proof-of-principle population suppression trial; and, 5) selection dynamics on the fsRIDL trait in caged populations. Olive fly fsRIDL strains were developed with full female-lethal penetrance and repressibility. The lead strain displayed similar life-history and sexual competitiveness traits to those of the wild-type strain from which they were derived. In addition, transgenic males showed photoperiod compatibility and strong sexual competitiveness with field-collected wild olive flies. The feasibility of the fsRIDL approach was demonstrated when repeated male releases caused eradication of caged olive fly populations. Although needing field confirmation, these results suggest that fsRIDL olive fly strains may help to mitigate key problems experienced in previous olive fly SIT trials, and could help form the basis of a renewed effort towards olive fly SIT control.

Les LT CD8 mémoires constituent une population hétérogène. Une modulation des différents signaux d’activation des LT CD8 naïfs influe sur la diversité des LT CD8 effecteurs et mémoires générés. A coté des sous populations classiquement décrites de LT CD8 mémoires développés dans des conditions infectieuses, il existe une population de LT CD8 mémoires générés dans des conditions d’inflammation stérile, c’est-à-dire en absence de pathogènes et de signaux moléculaires dérivés de pathogènes : les TIM pour « T-inflammatory memory cells ». Au cours de cette thèse j’ai eu pour objectif : 1) de mieux caractériser la population de TIM 2) d’évaluer leur capacité à répondre à une activation par un pathogène viral et ainsi leur plasticité et 3) d’étudier leur recrutement au site d’une infection locale respiratoire.J’ai ainsi pu identifier de nouvelles propriétés des TIM et montrer que les TIM sont recrutés dans une réponse secondaire à un virus exprimant la même spécificité antigénique, en générant des LT CD8 mémoires secondaires aux fonctions améliorées. De plus, les LT CD8 mémoires secondaires générés présentent un avantage fonctionnel par rapport aux LT CD8 mémoires primaires dans leur capacité de production de TNF-α et de la chimiokine XCL1. Cette dernière propriété pourrait leur conférer un avantage pour la réponse à des antigènes cross présentés. J’ai par ailleurs montré la capacité des TIM à être recrutés au niveau du poumon et des voies aériennes au cours d’une infection respiratoire virale. Ces résultats montrent que les LT CD8 mémoires générés dans des conditions d’activation inflammatoires stériles peuvent prendre part au contingent de cellules immunitaires impliquées dans des réponses à des infections. Ces résultats ouvrent un champ d’investigation intéressant concernant la plasticité des LT CD8 mémoires. Ils pourraient avoir une incidence sur certaines pathologies inflammatoires, dans le cas d’une ré-activation des TIM par un virus cross réactif. / Memory CD8 T cells represent a heterogeneous population. A modulation of the activation signals during naïve CD8 T cells activation influences the diversity of the Effector and Memory CD8 T cells generated. Besides the classically described subsets of Memory CD8 T cells, generated under infectious conditions, are T inflammatory memory CD8 T cells (TIM). TIM are generated under sterile priming conditions that are devoid of pathogens and pathogen-derived danger signals.During this thesis, I had the latter objectives: 1) a better characterisation of TIM, 2) to evaluate whether they could be recruited in an immune response directed against a virus and thus investigate their plasticity, 3) to examine their recruitment to the site of a respiratory local infection.I have identified new features of TIM and shown that TIM can take part to the immune response triggered by a virus expressing their cognate antigen and further differentiate into secondary memory cells with improved functions. The secondary memory CD8 T cells they generate display a functional advantage over primary memory cells in their capacity to produce TNF-α and the XCL1 chemokine. This last result could give them an advantage against cross-presented antigen. Furthermore, I have shown that TIM cells can be recruited in lung and airways during a respiratory viral infection. These results show that memory CD8 T cells generated under sterile priming conditions can take part to the contingent of immune cells involved in responses to infection. They open an interesting field of investigation of the plasticity of memory CD8 T cells. They could have an impact in inflammatory diseases, in the case of re-activation of TIM by a cross-reactive virus.

A diabetes tipo 1 (DT1) está associada `a inflamação estéril (IE) e maior susceptibilidade a sepse. A sepse induz a síndrome da resposta inflamatória sistêmica (SIRS) e a inflamação pulmonar aguda (ALI). O leucotrieno (LT) B4 produzido condições inflamatórias induz a expressão de MyD88 em macrófagos (MA). Hipotetizamos que a DT1 induz a síntese de LTB4 promovendo a IE e isto contribui para SIRS, susceptibilidade a sepse e ALI. Os diabéticos apresentaram níveis elevados de LTB4 e IL-1b no soro e seu MA expressaram mais MyD88/STAT-1. A expressão de STAT-1 foi induzida por c-Jun de forma dependente de LTB4. O tratamento com insulina restaurou os níveis de LTB4 e STAT-1/MyD88 e a inibição de LTB4 restaurou os níveis de MyD88 e IL-1b. Na sepse, a inibição de 5LO prolongou a sobrevida dos diabéticos e diminuiu a SIRS menos IL-1b e IL-10 no soro e TNF-a e IL-1b na cavidade peritoneal. O pulmão dos diabéticos apresentaram ALI menos intensa que se correlacionou com um altos níveis de SOCS-1, baixos níveis de MyD88 e falha na ativação de NFkB nos macrófagos alveolares. / Type 1 diabetes (T1D) is associated with sterile inflammation (SI) and increased sepsis susceptibility. Sepsis induces Systemic Inflammatory Response Syndrome (SIRS) and Acute Lung Injury (ALI). Leukotriene (LT) B4 is produced in inflammatory conditions and induces MyD88 expression in macrophages (MA). We hypothesized that T1D induce LB4 that promotes SI contributing to SIRS, sepsis susceptibility and ALI. Diabetics presented higher levels of LTB4 and e IL-1b in the serum and MA expressed more MyD88/STAT-1. STAT-1 expression was induced by c-Jun on LTB4 dependent manner. Insulin treatment restored LTB4 and STAT-1/MyD88 levels and inhibition of LTB4 restored MyD88 and IL-1b levels. During sepsis, 5LO inhibition increased diabetics survival and inhibited SIRS- lower levels of IL-1b and IL-10 in the serum and TNF-a and IL-1b in the peritoneal cavity. Lungs from diabetics presented milder ALI that correlated with high levels of SOCS-1, low levels of MyD88 and impaired NFkB activation in alveolar macrophages.

Introdução: O Centro de Material e Esterilização (CME) deve garantir a remoção completa de resíduos orgânicos e inorgânicos, sobretudo detergentes e endotoxinas, dos produtos críticos para saúde por meio do enxágue suficiente com água de qualidade. Com base nos recentes relatos de síndromes tóxicas do segmento anterior ocular, que foram associadas às más práticas de processamento do instrumental de oftalmologia, especialmente, a qualidade da água utilizada em seu enxágue final, esta Tese teceu a hipótese de que quanto mais pura for a qualidade da água do último enxágue, menor será a citotoxicidade encontrada nos produtos para saúde. Objetivo: Avaliar a citotoxicidade de cânulas de hidrodissecção submetidas à contaminação desafio, limpeza automatizada com enxágue final em diferentes qualidades de água: de torneira, tratada por deionizador, por destilação, por osmose reversa e por ultrapurificação. Métodos: 130 cânulas de hidrodissecção foram usadas, 26 por grupo experimental, caracterizados, de acordo com a água utilizada no último enxágue. As amostras foram submetidas à contaminação desafio interna e externamente por uma solução contendo 20% sangue de carneiro desfibrinado e 80% de Cloreto de Sódio a 0,9%, para simular um cenário desafiador de sujidade no material cirúrgico oftalmológico, sendo em seguida processadas, de acordo com um procedimento operacional padrão validado para este tipo de cânula, variando-se apenas a qualidade de água no enxágue final. Como controle positivo, foram utilizadas três cânulas descartáveis, que foram submetidas ao mesmo procedimento de contaminação desafio, imersas em uma solução contendo água de torneira e detergente enzimático que, após a evaporação da solução, foram esterilizadas. Para o controle negativo, foram usadas três cânulas das mesmas utilizadas nos grupos experimentais, com o mínimo de manipulação e na forma como foram fornecidas pelo fabricante, tendo sido apenas esterilizadas. Adicionalmente, foi incluído um grupo comparativo, no qual três amostras foram processadas em condições idênticas às dos grupos experimentais, enxaguadas com água de torneira, porém, sem secagem. Sequencialmente, procedeu-se a realização do teste de citotoxicidade pela incorporação do corante vital vermelho neutro para a obtenção da média da viabilidade celular de cada grupo experimental. Resultados: Ausência de citotoxicidade nos extratos das amostras, independente da diluição considerada na análise, sendo 83% a porcentagem média de viabilidade celular mínima obtida no extrato das amostras enxaguadas com água tratada por destilação na diluição de 12,5%. Conclusão: As cânulas de hidrodissecção não demonstraram citotoxicidade, independentemente da qualidade de água utilizada no último enxágue. Os resultados apresentados puderam ser alcançados unicamente por meio do uso de um procedimento operacional padrão de limpeza validado, baseado em literatura científica, em recomendações oficiais e na legislação relacionada. / Introduction: The Central Sterile Supply Department (CSSD) must guarantee the complete removal of organic and inorganic waste, especially detergents and endotoxins, from critical medical devices through sufficient rinsing with good-quality water. Based on recent reports of toxic anterior segment syndromes, which were associated with poor processing practices of ophthalmology instruments, particularly the quality of water used in the final rinse, this thesis has raised the hypothesis that the better the quality of the water used in the last rinse, the lower the cytotoxicity found in medical devices. Objective: To evaluate the cytotoxicity of hydrodissection cannulas, that were submitted to contamination challenge and then automated cleaning with final rinse in different qualities of water: tap water, water treated by a deionizer device, by distillation, by reverse osmosis and by ultrapurification. Methods: 130 hydrodissection cannulas were used, 26 per experimental group, characterized according to the last rinse water used. The samples were submitted to internal and external contamination challenge using a solution containing 20% defibrinated sheep blood and 80% Sodium Chloride at 0.9%, to simulate a challenging scenario of soiled ophthalmic surgical material, which was then processed, according to a validated standard operating procedure for this type of cannula, changing only the quality of water at the final rinse. Three disposable cannulas were used as positive controls, being submitted to the same contamination challenge procedure, then immersed in a solution containing tap water and enzymatic detergent, and then sterilized after evaporation of the solution. Three cannulas, identical to those used in the experimental groups, were used as negative controls, after minimum handling and exactly as they were supplied by the manufacturer, having only been sterilized. Additionally, a comparison group was included, from which three samples were processed under conditions identical to the experimental groups, rinsed with tap water, but without drying. Sequentially, the cytotoxicity assay was performed by incorporating the neutral red vital dye to obtain mean cell viability from each experimental group. Results: We observed absence of cytotoxicity in the sample extracts, regardless of the dilution considered in the analysis, with 83% of minimal cell viability obtained in the sample extract rinsed with distilled water at 12.5% dilution. Conclusion: Hydrodissection cannulas showed no cytotoxicity, regardless of the quality of water used in the final rinse. The results shown here were achieved by using a validated cleaning standard operating procedure based on scientific literature, official recommendations and related legislation.

Introdução: A insuficiência de métodos de dimensionamento que considerem a especificidade do processo de trabalho desenvolvido nas unidades de Centro de Material e Esterilização (CME) tem dificultado a provisão adequada de profissionais de enfermagem na área. Objetivo: Propor um método para o dimensionamento de profissionais de enfermagem em CME, a partir das atividades validadas no estudo de Costa(1). Método: Trata-se de um estudo de natureza quantitativa, do tipo desenvolvimento metodológico, realizado em quatro CMEs de instituições hospitalares públicas e privadas, de grande porte, da cidade de São Paulo. Participaram da pesquisa os profissionais que executaram ações relacionadas ao processamento de materiais nos CMEs, durante a coleta de dados. A pesquisa foi desenvolvida em quatro etapas: mapeamento das atividades em posições de trabalho; determinação do tempo padrão de processamento dos materiais em cada posição de trabalho; estabelecimento da carga média diária de trabalho em cada posição de trabalho; cálculo do quantitativo de profissionais de enfermagem em CME. Resultados: As atividades foram mapeadas em 15 posições de trabalho relacionadas à cinco áreas de trabalho do CME. Para a obtenção do valor médio de tempo de cada posição de trabalho foram mensuradas 1315 amostras de ciclos de trabalho. O tempo padrão de processamento de materiais em cada posição de trabalho foi determinado a partir do resultado do tempo médio de processamento dos kits, acrescentando-se os valores correspondentes ao ritmo do trabalhador e de tolerância para o atendimento das necessidades pessoais e de fadiga. No CME I a carga média de trabalho diária obtida foi de 217,4 horas; no CME II o resultado foi de 294,0 horas; no CME III obteve-se um valor de 123,1 horas e no CME IV a carga média de trabalho foi de 189,1 horas. Para comparar o quadro de pessoal esperado, obtido por meio do método e dos parâmetros propostos, com o quadro de pessoal observado nos CMEs, foi realizado o teste do Qui quadrado (C2) ao nível de significância de 5%. O resultado desse teste possibilitou afirmar que o valor calculado não difere do valor observado em todas as unidades de CME. Conclusão: A presente investigação possibilitou propor, além de parâmetros de tempo para determinação da carga de trabalho, um método para o dimensionamento de pessoal em CMEs, e apresenta-se como um importante referencial que poderá auxiliar as enfermeiras na elaboração e justificativa de propostas consistentes para o planejamento, alocação e distribuição de profissionais de enfermagem nessas unidades / Introductions: The paucity of quantification methods that take into consideration the specificity of the work process carried out in Sterile Processing Departments (SPD) has hindered the adequate staffing with nursing professionals in this area. Objective: to propose a method to calculate requirements of nursing professionals in the SPD based on the activities validated in the study by Costa(1). Method: This is a quantitative study for methodological development, carried out in four Sterile Processing Departments of large public and private hospitals in the city of São Paulo. Professionals performing all tasks related to the processing of materials in the SPDs participated in data collection. The study was carried out in four stages: mapping of activities in work positions, quantification of standard time for processing of materials in each work position, determination of average daily workload in each position, calculation of the nursing professionals requirements in the SPD. Results - Activities were defined in 15 work positions related to the five work areas of the SPD. To obtain the average time necessary for each work position, 1315 work cycle samples were measured. Standard time for processing materials in each work position was based on average processing time of kits, in addition to the values referring to worker rhythm and tolerance for personal needs and fatigue. In SPD I average daily workload was 217.4 hours, in SPD II it was 294.0 hours, in SPD III it was 123.1 hours and SPD IV the average workload was 189.1 hours. Chi-square test, with significance of 5%, was used in order to compare the estimated staff requirements, obtained according to the proposed methodology and parameters, to the actual staff. Test results show that estimated values are not different from actual values found in SPDs studied. Conclusion: The present study allowed us to propose time parameters to determine workload, as well as a method to calculate staffing requirements in SPDs and represents an important reference to help nurses to design and justify consistent proposals to estimate, allocate and distribute nursing professionals in these departments

Le détecteur Borexino, situé au laboratoire souterrain du Gran Sasso (LNGS), mesure les neutrinos solaires depuis 10 ans. Parmi les neutrinos solaires, le spectre continu du 8B jusqu’à 17 MeV permet de tester la zone de transition de l’effet de résonance dans la matière dit effet MSW. Cette nouvelle analyse augmente d’un ordre de grandeur la statistique par rapport à la précédente mesure de Borexino publiée en 2011. Pour ce faire, l’ensemble du volume scintillant a été inclus dans l’analyse, aucune coupure géométrique n’ayant été effectué au dessus de 5 MeV. Cela a permis l’identification d’un nouveau bruit de fond non pris en compte précédemment. L’ensemble des bruits de fond au dessus de 3 MeV est maintenant compris et la composante neutrino peut-être extraite d’un fit radial du détecteur. Afin de tester l’existence d’un neutrino stérile léger, une source de 3-5,5 PBq de 144Ce sera installée sous Borexino au début de l’année 2018 pour un an et demi de prise de données : c’est l’expérience CeSOX. Cette source est produite par PA MAYAK par purification de combustible nucléaire usagé, par conséquent les potentiels contaminants radioactifs sont très nombreux et peu contraints. Pour tester l’hypothèse stérile, une mesure en flux, une mesure en forme et une mesure combinée seront effectuées dans l’ensemble du détecteur Borexino. Ces mesures sont fortement dépendantes de la connaissance intime de la source (composition, forme du spectre beta du 144Ce, énergie moyenne 144Ce et 144Pr). A cette fin, un spectromètre gamma a été spécifiquement étalonné et entièrement simulé au CEA, Saclay. De même un spectromètre beta a été dessiné, assemblé, simulé et est en cours d’étalonnage. Finalement, des mesures de spectrométrie alpha et de masse seront réalisés sur des échantillons représentatifs envoyés au CEA, Saclay afin de contraindre au mieux la composition de la source de 144Ce de SOX. / Located in the Gran Sasso underground laboratory (LNGS), Borexino measures solar neutrinos for 10 years. Among solar neutrinos, 8B continuous spectrum (up to 17 MeV) enables to test the transition zone between vacuum and matter regime of the MSW effect. This new measurement increases by one order of magnitude the exposure with respect to previous Borexino publication. To do so, the entire active volume is considered in this analysis above 5 MeV. A new background has been identified and a radial fit is done above 3 and 5 MeV enabling to extract the neutrino component. Existence of a light sterile neutrino would have important consequences on astrophysics and cosmology. SOX is the only experiment aiming at testing this hypothesis using a punctual radioactive source. A 3-5.5 PBq 144Ce source is actually under production and will be positioned under Borexino in 2018. Precise knowledge of the source is one of the main challenge of this experiment, based on rate and shape neutrino measurement. Two critical parameters are the heat released by the source for activity measurement and the expected neutrino spectrum in the detector. We first describe the SOX experiment insisting on 144Ce source production. Then, we focus on Saclay installations dedicated to constrain radioactive contamination inside the source using representative samples. Alpha, gamma and mass spectroscopy calibration and simulation are discussed and competitive constrains are derived. A status on 144Ce beta shape measurements is done as well as presentation of future measurement.

[pt] Nesse trabalho realizamos, em princípio, um estudo fenomenológico de alguns experimentos prévios com neutrinos, que utilizaram reatores nucleares como fonte. Tais experimentos buscaram evidências de distorção espectral que corroborassem o mecanismo de conversão de sabor entre neutrinos. Nessa etapa reunimos suficiente informação sobre a metodologia empregada para a detecção e análise do espectro de neutrinos de reatores, bem como os limites impostos por esses experimentos sobre os parâmetros de oscilação. A partir desse estudo, investigamos a possibilidade de se explorar uma região do espaço de parâmetros, caracterizada por um pequeno ângulo de mistura e elevado autoestado de massa, ainda não excluída pelos resultados experimentais atuais. Como uma escala de massa tão elevada não pode estar associada a qualquer um dos três sabores ativos (eletrônico, muônico ou tauônico), em nossa análise, utilizamos uma extensão do modelo de três neutrinos ativos, incorporando um quarto autoestado estéril. Por fim, discutimos uma configuração experimental, baseada em um reator nuclear, que apresente a sensibilidade necessária para atingir esse conjunto de parâmetros. / [en] In this dissertation we have done, at first, a phenomenological study of some previous neutrino experiments, that had searched evidences of spectral distortion that corroborated the mechanism of flavor conversion, using nuclear reactors as source. We collected enough information about the methodology used for detection and analisys of neutrino spectrum of reactors, as well as the constraints on oscillation parameters provided by that experiments. Starting from this study, we investigated the possibility to explore a region of the space of parameters, characterized by a small mixing angle and high mass eigenstate, that not yet have been excluded by experimental results, but incompatible with the extracted current mass scale of the experiments with solar, atmospheric, accelerator (except for the LSND experiment) and reactor neutrinos. For this inquiry, we assume the simplest extension of the standart oscillation model, incorporating a new eigenstate responsible for the higher scale mass. Finally, we discuss a experimental configuration, based on nuclear reactor, which presents the sensitivity required to reach this set of parameters.