Neutrino physics has entered a precision era in which understanding backgrounds and systematic uncertainties is particularly important. With a precise understanding of neutrino physics, we can better understand neutrino sources. In this work, we demonstrate dependency of single detector oscillation experiments on reactor neutrino flux model. We fit the largest reactor neutrino flux model error, weak magnetism, using data from experiments. We use reactor burn-up simulations in combination with a reactor neutrino flux model to demonstrate the capability of a neutrino detector to measure the power, burn-up, and plutonium content of a nuclear reactor. In particular, North Korean reactors are examined prior to the 1994 nuclear crisis and waste removal detection is examined at the Iranian reactor. The strength of a neutrino detector is that it can acquire data without the need to shut the reactor down. We also simulate tau neutrino interactions to determine backgrounds to muon neutrino and electron neutrino measurements in neutrino factory experiments. / Ph. D.

L'objectif de cette thèse est la recherche des neutrinos cosmiques de haute énergie émis par des sources ponctuelles avec le télescope à neutrino ANTARES. La détection des neutrinos cosmiques de haute énergie peut apporter des réponses à des problèmes importants comme l'origine des rayons cosmiques et les procédures d'émission des rayons gamma. Dans la première partie de la thèse, le flux des neutrinos émis par des sources galactiques et extragalactiques et le nombre des évènements qui peut être détecté par ANTARES sont estimés. Cette étude utilise les spectres des rayons gamma des sources connues en tenant compte de l'absorption de ces rayons par la lumière extragalactique diffuse. Dans la deuxième partie de la thèse, le pointage absolu du télescope ANTARES est étudié. Étant situé à une profondeur de 2475 m dans l'eau de mer, l'orientation du détecteur est déterminée par un système de positionnement acoustique qui utilise des ondes de basse et haute fréquences entre la surface de la mer et le fond. La troisième partie de la thèse est la recherche des sources ponctuelles de neutrinos avec les données d'ANTARES. L'algorithme de recherche est basé sur une méthode de maximisation du rapport de vraisemblance. Il est utilisé dans deux stratégies de recherche; "la stratégie de recherche avec des sources candidates" et "la stratégie de recherche dans tout le ciel". L'analyse des données de 2007+2008 n'a pas marqué une découverte. Les meilleures limites supérieures au monde sur les flux de neutrinos provenant des différentes sources dans l'Hémisphère Sud sont établies. / The aim of this thesis is the search for high energy cosmic neutrinos emitted by point sources with the ANTARES neutrino telescope. The detection of high energy cosmic neutrinos can bring answers to important questions such as the origin of cosmic rays and the gamma rays emission processes. In the first part of the thesis, the neutrino flux emitted by galactic and extragalactic sources and the number of events which can be detected by ANTARES are estimated. This study uses the measured gamma ray spectra of known sources taking into account the gamma ray absorption by the extragalactic background light. In the second part of the thesis, the absolute pointing of the ANTARES telescope is evaluated. Being located at a depth of 2475 m in sea water, the orientation of the detector is determined by an acoustic positioning system which relies on low and high frequency acoustic waves measurements between the sea surface and the bottom. The third part of the thesis is a search for neutrino point sources in the ANTARES data. The search algorithm is based on a likelihood ratio maximization method. It is used in two search strategies; "the candidate sources list strategy" and "the all sky search strategy". Analysing 2007+2008 data, no discovery is made and the world's best upper limits on neutrino fluxes from various sources in the Southern sky are established.

T2K is a long-baseline accelerator neutrino oscillation experiment using the high-intensity ν_μ beam produced at J-PARC. Sitting 295 km away, the giant Super-Kamiokande detector, a 50 kt water tank instrumented with 11,129 photosensitive detectors, sees a narrow band beam peaked at 600 MeV. The baseline to energy ratio is finely tuned for studying neutrino oscillations at the atmospheric neutrino squared-mass splitting. The beam is also sampled 280m downstream of the neutrino production target by a series of finely segmented solid scintillator and time projection chamber detectors. Observing changes in the neutrino beam between the two detectors allows oscillation parameters to be accurately extracted. A ν_μ-disappearance analysis was performed on the combined T2K Run 1+2+3+4 dataset, corresponding to integrated J-PARC neutrino beam exposure of 6.57x10²⁰ POT, in a framework of three active neutrino flavour oscillations including matter effects in constant-density matter. The observed reconstructed energy spectrum of 1 μ-like ring events was fitted, and separate fits were made for the normal and the inverted mass hierarchies.

The liquid-scintillator neutrino-detector (LSND) and mini booster neutrino experiment (MiniBooNE) experiments claim to observe the oscillation ῡ_µ→ ῡ_e, which can only be explained by additional neutrinos and is a claim that must be further tested. This thesis proposes a new accelerator and experiment called νSTORM to refute or confirm the oscillation these claims by studying the CPT-equivalent channel ν_e→ν_µ. A 3.8-GeV/c muon decay ring is proposed with neutrino detectors placed 20 m and 2000 m from the decay ring. The detector technology would be a magnetized iron sampling calorimeter, where the magnetic field is induced by a superconducting transmission line. In a frequentist study, the sensitivity of this experiment after 5 years would be >10σ. The range of the thesis discussion starts with the proton front-end design and ends with neutrino parameter estimation. After describing the phenomenology of sterile neutrinos, the facility and detector performance work is presented. Finally, the systematics are explained before the sensitivity and parameter-estimation works are explained.

Doctor of Philosophy / Department of Physics / Glenn Horton-Smith / In March 2012, the Double Chooz reactor neutrino experiment published its most precise result so far: sin[superscript]2 2theta13 = 0.109 +/- 0.030(stat.) +/- 0.025(syst.). The statistical significance is 99.8% away from the no-oscillation hypothesis. The systematic uncertainties from background and detection efficiency are smaller than the first publication of the Double Chooz experiment. The neutron detection efficiency, one of the biggest contributions in detection systematic uncertainties, is a primary topic of this dissertation. The neutron detection efficiency is the product of three factors: the Gd-capture fraction, the efficiency of time difference between prompt and delayed signals, and the efficiency of energy containment. [superscript]252 Cf is used to determine the three factors in this study. The neutron detection efficiency from the [superscript]252 Cf result is confirmed by the electron antineutrino data and Monte Carlo simulations. The systematic uncertainty from the neutron detection efficiency is 0.91% used in the sin[superscript]2 2theta13 analysis. The seasonal variation in detector performance and the seasonal variations of the muon intensity are described in detail as well. The detector stability is confirmed by observation of two phenomena: 1) the [electron antineutrino] rate, which is seen to be uncorrelated with the liquid scintillator temperature, and 2) the daily muon rate, which has the expected correspondence with the effective atmospheric temperature. The correlation between the muon rate and effective atmospheric temperature is further analyzed in this thesis to determine the ratio of kaon to pion in the local atmosphere. An upper limit on instability of the neutron detection efficiency is established in the final chapter. The systematic error, 0.13%, from the relative instability is the deviation of the calibration runs. This thesis concludes with the potential systematic errors of neutron detection efficiency and estimation of how these potential systematic errors affect the result of sin[superscript]2 2theta13.

Doctor of Philosophy / Department of Physics / Timothy A. Bolton / This dissertation presents the first topological study of the charge current quasi-elastic (CCQE) neutral hyperon production induced by antineutrinos in the ArgoNeuT detector, a liquid argon time projection chamber (LArTPC) at Fermilab, using 1.20 × 10²⁰ protons-on- target (POT), in the NuMI beam operating in the low energy antineutrino mode. The total cross section for the CCQE neutral hyperon production is reported at the mean production energy of 3.42 GeV. The event yield in data is consistent with the predicted cross section, σ = 2.7 × 10−40 cm²: σ(CCQE[subscript Λ0+Σ0] ) = (3.7 ± 1.9(stat.) ± 1.5 (sys.)) × 10⁻⁴⁰ cm². The study sets a 90% confidence level (C.L.) upper limit on the total cross section of CCQE neutral hyperon production: σ(CCQE[subscript Λ0+Σ0] ) < 7.3 ×10⁻⁴⁰ cm² at 90% C.L.

In order to be able to determine neutrino mass hierarchy in the neutrino oscillation experiment JUNO we need to understand the dependence of the response of the signal from the scintillator on the deposited energy inside the scintillator. We measure the nonlinearity of the signal response via the Compton scattering inside the scintillator and via the precision gamma spectroscopy inside the HPGe detector. We observe effects of different parameters on the experiment via the Monte Carlo simulations. We also improve the data processing of the measured data and discuss what improvements of the experiment we can use in the future.

This thesis describes the search for neutrino-production of single photons using the off-axis near detector at 280 metres (ND280) of the T2K experiment. A photon selection is used to perform the searches using the first Fine Grained Detector (FGD1) of the ND280. The thesis also highlights the importance of systematic uncertainties in the analysis, since the selection is background dominated. After careful characterisation of the systematic uncertainties and estimation of the efficiency, it is concluded that, with the selected 39 data events and the expected background of 45 events, the limit for neutrino-induced single photons, at T2K energies, is 0:0903 x 10-38cm2/nucleon. This result can be compared with the expected limit of 0:1068 x 10-38cm2/nucleon. Using ND280's neutrino energy distribution (peaked at 600 MeV), NEUT predicts a flux-averaged cross section of 0:000239 x 10-38cm2/nucleon. A fit to the muon and electron (anti-) neutrinos selections in the ND280 was performed. The aim of this analysis is to use a data-driven method to constrain the electron (anti-) neutrinos background events at SK, the far detector and electron neutrino cross section parameters for oscillation analyses. These are fundamental inputs in the context of the searches for Charge-Parity (CP) violation in the neutrino sector. After a fit to the nominal Monte Carlo was realised, the electron neutrino and anti-neutrino cross section normalisation uncertainties are found to be 7.6% and 19.3%, repectively. Although these numbers are much higher than the assumed 3% uncertainty of all the CP violation searches performed at T2K up to now, the difference in the δCP log-likelihood is found to be acceptable as the one sigma contours are not very different and the exclusion of the δCP = 0 is roughly the same.

The observation of solar and atmospheric neutrino oscillations place bounds on the mass differences. However, these probes are insensitive to the absolute mass. To date, cosmology has provided the best bounds on the total neutrino mass. These bounds are based on a degenerate mass model. With the increasing precision of cosmological data, we investigate the effect of the neutrino mass hierarchy. The precision of the parameter estimates stems from precise observations of the cosmic microwave background. However, the effect of neutrino mass hierarchy on this observation is smaller than the cosmic variance. Therefore, we rely on the measurement of the matter power spectrum for hierarchy effects. We propose the use of importance sampling rather than the commonly used Markov chain Monte Carlo. Importance sampling takes advantage of the microwave background's statistical insensitivity to hierarchy. We present forecasted bounds due to Planck and the proposed CMBPol. We also discuss the needed precision for future galaxy surveys in detecting the effect of neutrino mass hierarchy. / text

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