T2K (Tokai to Kamioka) est une expérience d’oscillation de neutrinos muoniques sur une longue ligne de base, située au Japon. Elle est conçue pour mesurer le changement de saveur des neutrinos d’un faisceau produit à l’aide d’un accélérateur au laboratoire JPARC de Tokai. Les détecteurs proche et lointain sont placés légèrement hors axe par rapport au faisceau. Depuis la découverte en 2013 de l’apparition de neutrinos électroniques, T2K a inversé la polarité des cornes magnétiques intervenant dans la production du faisceau, afin de produire un faisceau d’antineutrinos et d’augmenter la sensibilité de l’expérience à la violation de la charge-parité dans le secteur leptonique. Le faisceau produit est alors dominé par les antineutrinos muoniques avec une composante mesurable de neutrinos muoniques. L’analyse simultanée, dans les données prises avec le faisceau de neutrinos et le faisceau d’antineutrinos, des interactions par courant chargé dans le détecteur proche ND280, permet de réduire l’impact sur les analyses d’oscillation des incertitudes liées au flux de (anti)neutrinos et à leur section efficace d’interaction. Les données de ND280 permettent également de mesurer les sections efficaces d’interaction des antineutrinos d’énergie proche de 600 MeV. La bonne connaissance du processus d’interaction des (anti)neutrinos avec les noyaux atomiques est cruciale pour interpréter les résultats de l’expérience en termes d’oscillations. De nombreux modèles théoriques ont été développés pour décrire les effets nucléaires lors des interactions des (anti)neutrinos, mais une vison globale cohérente n’a pas encore émergé. En particulier, des mesures variées de section efficace d’interaction par courant chargé sans production de pion dans l’état final suggèrent la possibilité pour les neutrinos d’interagir avec des paires de nucléons corrélés, entrainant l’éjection de plus d’un nucleon hors du noyau (composante dite “multi-nucléon”). Divers modèles ont proposé des estimations différentes de ce processus et une mesure précise et sans ambiguité n’est pas encore disponible. Ce travail de thèse se concentre sur trois études. La première détaille la sélection des interactions de neutrinos muoniques par courant chargé dans le détecteur proche hors axe. Dans un premier temps l’échantillon de données était divisé en deux selon le nombre de traces chargées de l’événement, puis l’accumulation de davantage de données a permis la séparation de l’échantillon en trois lots selon le contenu en pions de l’événement. La seconde étude consiste en la mesure simultanée de la section efficace d’interaction des neutrinos et des antineutrinos muoniques par courant chargé, conduisant à un état final sans pion mesuré dans le détecteur ND280. Ces sections efficaces sont extraites en fonction de l’impulsion et de l’angle du muon issu de l’interaction, permettant ainsi d’évaluer la somme, la différence et l’asymétrie entre les sections efficaces des neutrinos et des antineutrinos. La somme permet d’isoler la composante d’interférence vecteur-axial de la section efficace, et la différence est sensible à la composante multi-nucléons. L’asymétrie permet d’estimer directement le biais éventuel sur la mesure de la phase de violation de CP dû à la modélisation des sections efficaces, dans l’analyse d’oscillation de neutrinos. La dernière partie de la thèse étudie la proposition d’utiliser la technologie dite de multi-PMT pour le detector Hyper-Kamiokande, version à plus grande échelle de Super-Kamiokande, ainsi que la possibilité d’étudier le flux de neutrinos avec un détecteur basé sur le rayonnement Cherenkov dans l’eau, et placé à environ 2 km de l’origine du faisceau de neutrinos. Un multi-PMT est une sphère de plastique contenant 26 tubes photomultiplicateurs, qui pourrait améliorer l’efficacité des futurs détecteurs basés sur le rayonnement Cherenkov dans l’eau. / T2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment installed in Japan and designed to measure neutrino flavor oscillation using an off-axis neutrino beam produced at the J-PARC accelerator facility in Tokai. Since its discovery of electron neutrino appearance in 2013, T2K has switched its beam magnet polarities to run in antineutrino beam mode in order to enhance its sensitivity to the charge-parity violation in the leptonic sector. The beam is dominated by muon antineutrinos, but it also contains a sizable contamination from muon neutrinos. The analysis of both neutrino and antineutrino charged-current interactions in the off-axis near detector ND280, provides a significant reduction of the flux prediction and cross-section modeling systematic uncertainties in the oscillation analysis. ND280 data also gives us the opportunity to measure antineutrinos cross-sections at the energy around 600 MeV. Information on (anti)neutrino scattering is vital for the interpretation of neutrino oscillation. Many theoretical models have been developed to describe the nuclear effects in (anti)neutrino scattering, but a consistent picture has yet to emerge. In particular, various measurements of charged-current cross-section without production of pions in the final state have suggested the presence of another channel where neutrinos interact with pairs of correlated nucleons and more than one nucleon is knocked-out from the nucleus (multi-nucleon component). Various models have proposed different estimations of such process and a precise and unambiguous measurement is not yet available. This thesis work is focused on three different arguments. First the selections of CC interactions of muon neutrinos in antineutrino beam in the off-axis near detector. In a first iteration this sample has been divided into two sub-sample based on the track multiplicity, then with more statistic a separation into three sub-samples based on the pion content in each event was possible. Then on the simultaneous measurement of the double-differential muon neutrino and antineutrino charged-current cross-section without pions in the final state using the off-axis near detector. The neutrino and antineutrino cross-sections will be simultaneously extracted as a function of muon momentum and angle with a likelihood fit, including proper estimation of the correlations, allowing the evaluation of the sum, difference and asymmetry between the two cross-sections. The sum isolates the axial-vector interference term of the cross-section, and the difference enhances the sensitivity to the multinucleon component. The asymmetry is a direct estimation on any possible bias due to mismodeling of (anti)neutrino interactions on the measurement of the CP violation phase in neutrino oscillation. The last topic concerns the proposal of the multi-PMT technology as detector for Hyper-Kamiokande, the upgrade of Super-Kamiokande, and the intermediate water v Cherenkov proposed to study the neutrino flux at ~2 $km$ from the beam production point. A multi-PMT is a plastic sphere filled with 26 photomultiplier tube that could improve the efficiency of the Cherenkov detectors foreseen in the future.

Since the first observation of antineutrinos from beta decay of the fission products inside a nuclear reactor in 1956, the design and operating experience of antineutrino detectors near reactors has increased to the point where monitoring the reactor's power level and progression through its burnup cycle has become possible. With the expected increase in world nuclear energy capacity, including the dissemination of reactor technologies to non-nuclear states, the need for safeguards measures which are able to provide continuous, near-real-time information about the state of the core, including its isotopic composition, in a tamper- and spoof-resistant manner is evident. Near-field (~20 m from the core) antineutrino detectors are able to fulfill this demand without perturbing normal reactor operation, without requiring instrumentation which penetrates the reactor vessel, and without displacing other plant structures. Two sodium-cooled long-life fast reactors that are characteristic of next-generation reactors which are attractive for installation in non-nuclear states, one large and one small power rating, have been modeled throughout their reference burnup cycles using MCC-3 and DIF3D/REBUS. Various diversions of fissile material from the core designed to obtain weapons-usable material for the purpose of nuclear proliferation were studied as perturbed core states. The difference in detector event rates between the reference and perturbed states was used to determine the probability that a particular diversionary activity would be apparent before the material could be converted into a weapon. These data indicate which types of diversion antineutrino safeguards are particularly strong against and how the technology might be implemented in current and future international policies concerning nuclear proliferation.

MINOS is a long baseline neutrino oscillation experiment. A manmade beam of predominantly muon neutrinos is detected both 1 km and 735 km from the production point by two functionally identical detectors. A comparison of the energy spectra measured by the two detectors shows the energy-dependent disappearance of muon neutrinos characteristic of oscillations and allows a measurement of the parameters governing the oscillations. This thesis presents work leading to measurements of disappearance in the 6% ∇_μ background in that beam. A calibration is developed to correct for time-dependent changes in the responses of both detectors, reducing the corresponding uncertainty on hadronic energy measurements from 1.8% to 0.4% in the near detector and from 0.8% to 0.4% in the far detector. A method of selecting charged current ∇_μ events is developed, with purities (efficiencies) of 96.5% (74.4%) at the near detector, and 98.8% (70.9%) at the far detector in the region below 10~GeV reconstructed neutrino energy. A method of using the measured near detector neutrino energy spectrum to predict that expected at the far detector is discussed, and developed for use in the ∇_μ analysis. Sources of systematic uncertainty contributing to the oscillation measurements are discussed. In the far detector, 32 ∇_μ events are observed below a reconstructed energy of 30 GeV, compared to an expectation of 47.8 for Δm̄²_atm = Δm²_atm, sin²(2‾θ₂₃) = sin²(2θ₂₃). This deficit, in such a low statistics sample, makes the result difficult to interpret in the context of an oscillation parameter measurement. Possible sources for the discrepancy are discussed, concluding that considerably more data are required for a definitive solution. Running MINOS with a dedicated ∇_μ beam would be the ideal continuation of this work.

Since the 1990s, researchers around the world have been creating antineutrino detectors for monitoring power reactors. These detectors have been deployed at light water reactors and are able to determine power levels and burn up throughout a fuel cycle. This technology could allow the IAEA to monitor LWRs remotely and unobtrusively to determine if they are operating using normal parameters. Very soon, the next generation of detector will be deployed at a CANDU reactor for a trial operation. While physical observation of these detectors is necessaryl in determining their usefulness, reactor physics simulations have proven to be very accurate in their prediction of detector performance. Since there are many designs still in development, reactor physics simulations are the only way to determine the efficacy of the detector technology. In addition to this, reactor simulations are the best way to evaluate the detector technology to ascertain its usefulness during diversion scenarios. In this research, antineutrino source terms were calculated for a High Temperature Gas Cooled Reactor core. These source terms were a function of power level and initial enrichment. SCALE6.1, developed by Oak Ridge National Laboratory, was used to calculate the isotopic inventory in the core as a function of depletion. These fertile and fissile isotopics, along with the fission cross-section and number of antineutrinos emitted per fission, were used to predict the antineutrino source rate for the core. It was found that changing the power yields a linear response from the antineutrino source term. By increasing the power by five percent, the source term also increased by five percent. Substantial changes in the initial enrichment also lead to a detectable change in the antineutrino source term. / Graduation date: 2012

Detection systems used to monitor reactor operations are of significant interest as tools for verification of operator declarations. Current reactor site safeguards are limited to visual inspections and intrusive monitoring systems. The recent development of antineutrino detectors may soon allow real-time monitoring from an unobtrusive location. Antineutrinos are produced through beta decay of fission products in the core. The lack of charge and small mass of the antineutrino ensures an extremely low interaction probability with all matter, effectively making the particle impossible to shield. As the fuel isotopic composition changes with burn-up, the primary fission source changes from ²³⁵U to ²³⁹Pu. Since differing antineutrino energy spectra are produced by each fissionable isotope, the antineutrino flux will also change as a function of burn-up. Supported by reactor simulations from nuclear codes, antineutrino detectors may provide a window into the reactor core and provide inspectors with tools to verify legitimate operations. This thesis is focused on the antineutrino rate produced by CANadian Deuterium Uranium reactors (CANDU) during startup. A CANDU fuel bundle model was created with the TRITON module from the SCALE6.1 code to calculate isotopic antineutrino rates for a single bundle. A full core CANDU model that incorporates refueling was also created for the first 155 days of operation after startup by using a Python 2.6 script to handle pre- and post-calculations. All simulations were calculated using operational data from Point Lepreau Generating Station produced by proprietary codes for the forthcoming fresh core startup. Dependence of the antineutrino rate on power and bundle replacement was analyzed, with a ±10% change in power causing a ±10% change in antineutrino rate, and the CANDU detector effectively measuring a 10% decrease in power within 9 hours of collection time. Bundle refueling was shown to only slightly modify the antineutrino rate, requiring a target volume more than 20 times larger than the present detector to effectively identify the change due to the bundles refueled over a one week period. Diversion of 15% or more of the total amount of bundles can be effectively measured by the CANDU detector within a one month counting period. / Graduation date: 2012

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19500号 / 理博第4160号 / 新制||理||1597(附属図書館) / 32536 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 教授 谷森 達, 准教授 市川 温子 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

The T2K ("Tokai-to-Kamioka") Experiment is a long-baseline neutrino oscillation experiment. A beam of primarily muon neutrinos (in neutrino beam mode) or antineutrinos (in antineutrino beam mode) is produced at the J-PARC ("Japan Proton Accelerator Research Complex") facility. The near detector (ND280), located 280 m from the proton beam target, measures a large event rate of neutrino interactions in the unoscillated beam, while the far detector, Super-Kamiokande, 295 km away, searches for the signatures of neutrino oscillation. This dissertation describes the analyses of data at ND280 and Super-Kamiokande leading to T2K's first results from running in antineutrino beam mode: a measurement of muon antineutrino disappearance. The measured values of the antineutrino oscillation parameters (Normal Hierarchy) are (sin²(θ̅₂₃), |Δm̅²₃₂|) = (0.450, 2.518 x 10ˉ³ eV²/c⁴), with 90% 1D confidence intervals 0.327 < sin²(θ̅₂₃) < 0.692 and 2.03 x 10ˉ³ eV²/c⁴ < |Δm̅²₃₂| < 2.92 x 10ˉ³ eV²/c⁴. These results are consistent with past measurements of these parameters by other experiments, and with T2K's past measurements of muon neutrinos. / Graduate

During the years between 1994 and 1997, the emulsion target of the CHORUS experiment was exposed to the wide band neutrino beam of the CERN SPS of 27 GeV average energy collecting about 106 neutrino interactions. A measurement of induced charm production and search for anticharmed pentaquark (0 c ) have been performed by using the presence of a 6% component in the beam. By requiring a positive muon charge as determined by the CHORUS muon spectrometer, 46 -induced charm events were observed with an estimated background of 5:20:4 events. At an average antineutrino energy of 18 GeV in the neutrino beam, the charm production rate induced by is

The T2K experiment is a long-baseline neutrino oscillation experiment, in which a muon neutrino beam is directed over a 295 km baseline from the J-PARC facility to the Super-Kamiokande detector. This allows neutrino oscillation to be studied in two channels: disappearance of &nu;_&mu; and appearance of &nu;_e. The T2K beam can be run either in neutrino or antineutrino configuration, for a neutrino beam which is predominantly composed of &nu;_&mu; or anti -&nu;_&mu; respectively. This thesis presents the first oscillation analysis to combine neutrino-mode and antineutrino-mode data sets, giving the first ever sensitivity to the CP-violating phase &delta;_CP from T2K data alone, as well as the most precise T2K measurement of the other neutrino oscillation parameters. The analysis uses a Markov Chain Monte Carlo method to construct a sample from the Bayesian posterior distribution, from which the oscillation parameters of interest and their uncertainties are estimated. Data samples from the T2K near detector, ND280, are fit simultaneously with data from the far detector in order to reduce the uncertainty in the far-detector prediction. When fitting the T2K data alone, the best-fit oscillation parameter values are sin² &theta;₂₃= 0.519^+0.031<sub style='position: relative; left: -2.8em;'>-0.059</sub>, sin² &theta;₁₃= 0.0257^+0.0106<sub style='position: relative; left: -3.2em;'>-0.0440</sub>, &Delta;m²<sub style='position: relative; left: -0.4em;'>32</sub>= 2.54^+0.12<sub style='position: relative; left: -2em;'>-0.10</sub> x 10^-3eV²,and &delta;_CP=-1.91 rad. The 90&percnt; credible interval for &delta;_CP excludes values around &pi;/2: &delta;_CP &notin; [0.38, 2.60] rad. When fitting the T2K data with a constraint on sin² &theta;₁₃ from measurements by reactor experiments, the best-fit oscillation parameter values are sin² &theta;₂₃= 0.519^+0.061<sub style='position: relative; left: -2.8em;'>-0.029</sub>, sin² &theta;₁₃= ^+0.0014<sub style='position: relative; left: -3.2em;'>-0.0014</sub>, Dm²<sub style='position: relative; left: -0.4em;'>32</sub>= 2.54^+0.12<sub style='position: relative; left: -2em;'>-0.12</sub> x 10^-3eV², and &delta;_CP=-1.72 rad. The 90&percnt; credible interval for &delta;_CP contains values &delta;_CP &isin; [-3.10,-0.17] rad, excluding the CP-conserving values 0 and ± &pi; at 90&percnt; probability.

Title: Prototype of detector for detection of reactor's antineutrinos Author: Lukáš Fajt Department: Institute of Particle and Nuclear Physics Supervisor: Doc. Ing. Ivan Štekl, CSc., IEAP, CTU in Prague Abstract: This master thesis is related to the development of the complex detector of reac- tor's antineutrinos, so called S3 , which is based on the polystyrene scintillation detectors. The detector S3 (dimensions 40 x 40 x 40 cm3 ) will be located in the close vicinity of a nuclear reactor (5-12 m) and its purpose will be to measure reactor's power, isotopic composition of the nuclear fuel and moreover verification of the sterile neutrino hypothesis by detecting reactor's antineutrinos via the Inverse Beta Decay (IBD) interaction. Within the thesis, the first prototype of the antineutrino detector was constructed. It is composed of 18 scintillation plates (40 x 20 x 1 cm3 ) and corresponding electronics. With this prototype the first test with cosmic muons were performed. Within the thesis, the energy reso- lution of the scintillation plates was significantly improved by the optimization of their chemical composition and selection of the optimal refractive material. The proper energy resolution is very important for the detector functionality. In addition, a new methods for the production of coating layer...