京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19501号 / 理博第4161号 / 新制||理||1598(附属図書館) / 32537 / 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

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21441号 / 理博第4434号 / 新制||理||1637(附属図書館) / 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 鶴 剛, 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

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The Precision Reactor Oscillation and SPECTrum Experiment (PROSPECT) is designed to probe short baseline oscillations of electron antineutrinos in search of eV-scale sterile neutrinos and precisely measure the U-235 reactor antineutrino spectrum from the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. The PROSPECT antineutrino detector (AD) provides excellent background rejection and position resolution due to its segmented design and use of Li-6-loaded liquid scintillator. In order to understand relative volume variation effects, which could affect an oscillation measurement, Ac-227 was added as a calibration source that was dissolved isotropically throughout the liquid scintillator. Using the correlated production of alphas from Rn-219 -> Po-215 -> Pb-211 in the Ac-227 decay chain I measured the rate of Ac-227 in each segment of the detector as well as the decay rate of Ac-227 events over the lifetime of the detector. The measured Ac-227 half-life suggests a rate of events falling 1.56 +/- 0.21% faster than expectation. The results of these studies were then applied as corrections to the measurement of antineutrino event rates as a function of distance from the reactor. This thesis will present the testing of Ac-227 as a calibration source before its addition to the AD, analysis methods, results of Ac-227 in the AD, and its application to the oscillation analysis. / Physics

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.

MINOS is a long-baseline neutrino oscillation experiment. It consists of two large steel-scintillator tracking calorimeters. The near detector is situated at Fermilab, close to the production point of the NuMI muon-neutrino beam. The far detector is 735 km away, 716 m underground in the Soudan mine, Northern Minnesota. The primary purpose of the MINOS experiment is to make precise measurements of the "atmospheric" neutrino oscillation parameters (Δm²_atm and sin²2θ_atm). The oscillation signal consists of an energy-dependent deficit of v_μ interactions in the far detector. The near detector is used to characterize the properties of the beam before oscillations develop. The two-detector design allows many potential sources of systematic error in the far detector to be mitigated by the near detector observations. This thesis describes the details of the v_μ-disappearance analysis, and presents a new technique to estimate the hadronic energy of neutrino interactions. This estimator achieves a significant improvement in the energy resolution of the neutrino spectrum, and in the sensitivity of the neutrino oscillation fit. The systematic uncertainty on the hadronic energy scale was re-evaluated and found to be comparable to that of the energy estimator previously in use. The best-fit oscillation parameters of the v_μ-disappearance analysis, incorporating this new estimator were: Δm² = 2.32^+0.12_-0.08 x 10^-3eV² sin²2θ > 0.90 (90% C.L.). A similar analysis, using data from a period of running where the NuMI beam was operated in a configuration producing a predominantly V‾_μ beam, yielded somewhat different best-fit parameters Δ‾m² = (3.36^+0.46_-0.40 (stat.}) ± 0.06(syst.)) x 10^-3eV², sin²2‾θ =0.86^+0.11_-0.12(stat.) ± 0.01(syst.). The tension between these results is intriguing, and additional antineutrino data is currently being taken in order to further investigate this apparent discrepancy.

T2K is a long baseline neutrino experiment which uses a beam of muon neutrinos, produced at J-PARC and detected at Super-Kamiokande, to study the neutrino oscillation parameters. The measurement of cross-sections in the T2K energies can constrain the uncertainties on the model predictions and help the oscillation analyses reach the necessary sensitivity to measure CP violation in the lepton sector. This thesis describes the measurement of the CC1 + cross-section in water using Run II-IV T2K data. The T2K near detector, ND280, is used to select a sample of CC1 + events having vertices in the water layers of the downstream ne-grained detector (FGD). The Time Projection Chambers (TPC) are used for the particle identi cation and to measure their momenta. The Electromagnetic Calorimeters (ECals) are used to reject events that produce electromagnetic showers coming from neutral pions. A Bayesian unfolding method with background subtraction and two control samples is used to extract the cross-section. The control samples constrain the background coming from interactions on carbon and deep inelastic scattering. The single di erential cross-section is presented as a function of the muon kinematics, the pion kinematics, the angle between the muon and the pion, and the reconstructed neutrino energy. A future long baseline experiment between J-PARC and Hyper-Kamiokande is presented as a natural continuation to the T2K experiment. Hyper- Kamiokande will be a next generation water Cherenkov detector with a total ( ducial) mass of 0.99 (0.56) million metric tons. A total exposure of 7.5MW 107 sec integrated beam power will lead to the measurement of CP to better than 19 degrees for all possible values of CP . CP violation in the lepton sector could be established at better than 3 (5 ) for 76% (58%) of the CP parameter space.

In this thesis, a number of aspects of neutrino oscillation physics are investigated, focusing on the design and phenomenology of next generation neutrino beam experiments. In working to optimise the sensitivity of the Hyper-Kamiokande experiment, new reconstruction software has been developed to meet the goal of fast, flexible reconstruction of particle positions, directions, energies and species. This is demonstrated for the TITUS intermediate detector, producing samples of neutrino interactions to constrain systematic uncertainties of oscillation analyses. Inclusion of these samples achieves a reduction of over 50% of systematic errors in measurements of 23 and and increases the parameter space for CP violation discovery after 10 years at 5 from 51% to 74%. A full analysis is presented of a potential neutron measurement at the E61 detector, including full simulations of all major backgrounds, a likelihood method of background removal, and a procedure for correcting for efficiency and backgrounds. Large, pure samples are produced, with the ability to accurately reproduce true distributions of neutron capture multiplicity, distance and angle relative to neutrino interactions, with true and reconstructed distributions agreeing within 2%. The sensitivities of Hyper-Kamiokande, including with a possible second tank in Korea, in combination with the DUNE experiment, have been thoroughly investigated. Several areas of strong synergy are identified, with the optimal combination of experiments possessing the ability to definitively resolve all remaining unknowns of 3-neutrino oscillations: determining both the octant of 23 and the mass-ordering in under 2 years and discovering CP violation at 5 for 50% of parameter space after 5 years. The highly predictive Littlest Seesaw flavour models of neutrino masses and mixing are tested against current oscillation data, finding no tension even at 1 . The ability of the next-generation experiments' oscillation measurements to probe these models is investigated, with all strands of the programme, including long baseline beam experiments and short and medium baseline reactor experiments, found to show high potential to exclude the models both individually and in combination.

A search for heavy Majorana neutrinos is performed using an event signature defined by two same-sign muons accompanied by two jets. This search is an extension of previous searches, (L3, DELPHI, CMS, ATLAS), using 19.7 fb-1 of data from the 2012 Large Hadron Collider experimental run collected by the Compact Muon Solenoid experiment. A mass window of 40-500 GeV/c2 is explored. No excess events above Standard Model backgrounds is observed, and limits are set on the mixing element squared, |VμN|2, as a function of Majorana neutrino mass. The Hadronic Forward (HF) Detector's performance will degrade as a function of the number of particles delivered to the detector over time, a quantity referred to as integrated luminosity and measured in inverse femtobarns (fb-1). In order to better plan detector upgrades, the CMS Forward Calorimetry Task Force (FCAL) group and the CMS Hadronic Calorimeter (HCAL) group have requested that radiation damage be simulated and the subsequent performance of the HF subdetector be studied. The simulation was implemented into both the CMS FastSim and CMS FullSim simulation packages. Standard calorimetry performance metrics were computed and are reported. The HF detector can expect to perform well through the planned delivery of 3000 fb-1.

During the last decades the standard model of particle physics has evolved to one of the most precise theories in physics, describing the properties and interactions of fundamental particles in various experiments with a high accuracy. However it lacks on some shortcomings from experimental as well as from theoretical point of view: There is no approved mechanism for the generation of masses of the fundamental particles, in particular also not for the light, but massive neutrinos. In addition the standard model does not provide an explanation for the observance of dark matter in the universe. Moreover the gauge couplings of the three forces in the standard model do not unify, implying that a fundamental theory combining all forces can not be formulated. Within this thesis we address supersymmetric models as answers to these various questions, but instead of focusing on the most simple supersymmetrization of the standard model, we consider basic extensions, namely the next-to-minimal supersymmetric standard model (NMSSM), which contains an additional singlet field, and R-parity violating models. R-parity is a discrete symmetry introduced to guarantee the stability of the proton. Using lepton number violating terms in the context of bilinear R-parity violation and the munuSSM we are able to explain neutrino physics intrinsically supersymmetric, since those terms induce a mixing between the neutralinos and the neutrinos. Since 2009 the Large Hadron Collider (LHC) at CERN explores the new energy regime of Tera-electronvolt, allowing the production of potentially existing heavy particles by the collision of protons. Thus the near future might provide answers to the open questions of mass generation in the standard model and show hints towards physics beyond the standard model. Therefore this thesis works out the phenomenology of the supersymmetric models under consideration and tries to point out differences to the well-known features of the simplest supersymmetric realization of the standard model. In case of the R-parity violating models the decays of the light neutralinos can result in displaced vertices. In combination with a light singlet state these displaced vertices might offer a rich phenomenology like non-standard Higgs decays into a pair of singlinos decaying with displaced vertices. Within this thesis we present some calculations at next order of perturbation theory, since one-loop corrections provide possibly large contributions to the tree-level masses and decay widths. We are using an on-shell renormalization scheme to calculate the masses of neutralinos and charginos including the neutrinos and leptons in case of the R-parity violating models at one-loop level. The discussion shows the similarities and differences to existing calculations in another renormalization scheme, namely the DRbar scheme. Moreover we consider two-body decays of the form chi_j^0 -> chi_l^\pm W^\mp involving a heavy gauge boson in the final state at one-loop level. Corrections are found to be large in case of small or vanishing tree-level decay widths and also for the R-parity violating decay of the lightest neutralino chi_1^0 -> l^\pm W^\mp. An interesting feature of the models based on bilinear R-parity violation is the correlation between the branching ratios of the lightest neutralino decays and the neutrino mixing angles. We discuss these relations at tree-level and for two-body decays chi_1^0 -> l^\pm W^\mp also at one-loop level, since only the full one-loop corrections result in the tree-level expected behavior. The appendix describes the two programs MaCoR and CNNDecays being developed for the analysis carried out in this thesis. MaCoR allows for the calculation of mass matrices and couplings in the models under consideration and CNNDecays is used for the one-loop calculations of neutralino and chargino mass matrices and the two-body decay widths. / Das heutige Standardmodell der Teilchenphysik ist eine der präzisesten Theorien der Physik, welche die Eigenschaften der bekannten Elementarteilchen und deren Wechselwirkungen in zahlreichen Experimenten mit hoher Genauigkeit beschreibt. Gleichwohl zeigt es Schwachpunkte auf experimenteller wie theoretischer Seite: Zwar gibt es mit dem Higgs-Mechanismus einen theoretischen Ansatz für die Erzeugung von Massen der Elementarteilchen im Standardmodell, jedoch ist dieser experimentell (noch) nicht nachgewiesen. Insbesondere benötigt das Standardmodell für die Erklärung der leichten Massen der Neutrinos noch eine Erweiterung. Darüber hinaus liefert das Standardmodell keinen Kandidaten für dunkle Materie, welche den dominanten Anteil der Materie im Universum ausmacht. Antworten auf viele dieser Fragestellungen liefern supersymmetrische Modelle, auf denen auch diese Arbeit fußt. Statt der einfachsten supersymmetrischen Realisierung des Standardmodells beschäftigen wir uns mit Erweiterungen, darunter das nächstminimale supersymmetrischen Standardmodell (NMSSM), welches ein zusätzliches Singletfeld enthält, sowie R-Paritätsverletzende Modelle. R-Parität ist eine diskrete Symmetrie, die die Stabilität des Protons in supersymmetrischen Erweiterungen garantiert. Die Nutzung von leptonzahlverletzenden Termen im Kontext von bilinearer R-Paritätsverletzung und dem munuSSM erlaubt die Erklärung von Neutrinodaten, da besagte Terme eine Mischung der Neutralinos mit den Neutrinos bewirken. Seit 2009 stößt der Large Hadron Collider'' (Großer Hardonenbeschleuniger, LHC) am CERN in Genf in den Energiebereich von Teraelektronenvolt vor und erlaubt so die Produktion von schweren, noch unbekannten Teilchen. Somit könnte die nahe Zukunft die Frage nach der Massenerzeugung im Standardmodell beantworten und Hinweise auf neue Physik liefern. Daher arbeiten wir die Phänomenologie der oben erwähnten supersymmetrischen Modelle an Beschleunigerexperimenten heraus und diskutieren die Unterschiede zur einfachsten supersymmetrischen Realisierung des Standardmodells. Im Falle von R-Paritätsverletzung können die Zerfälle des leichtesten Neutralinos Vertices mit Abstand zum Wechselwirkungspunkt erzeugen. In Kombination mit leichten singletartigen Teilchen können diese Zerfälle eine reiche Phänomenologie bereithalten wie beispielsweise Higgszerfälle in leichte singletartige Neutralinos, welche vor ihrem Zerfall eine messbare Strecke im Detektor zurücklegen. In dieser Arbeit präsentieren wir auch Rechnungen in der nächsthöheren Ordnung Störungs-theorie, da Einschleifenbeiträge große Korrekturen zu den Massen und Zerfallsbreiten auf Baumgraphenniveau liefern können. Wir berechnen die Massen von Neutralinos und Charginos, welche im Falle der R-Paritätsverletzung Neutrinos und Leptonen beinhalten, in nächsthöherer Ordnung und heben die Gemeinsamkeiten und Unterschiede zu exisitierenden Rechnungen in anderen Renormierungsschemata hervor. Darüberhinaus betrachten wir Zweikörperzerfälle der Form chi_j^0 -> chi_l^\pm W^\mp auf Einschleifenniveau. Im Falle von verschwindenden Zerfallsbreiten auf Baumgraphenniveau können die Korrekturen groß werden, genauso auch für die $R$-Paritäts-verletzenden Zerfälle des leichtesten Neutralinos chi_1^0 -> l^\pm W^\mp. Ein Charakteristikum von Modellen basierend auf bilinearer R-Paritätsverletzung ist die Korrelation zwischen den Verzweigungsverhältnissen der leichtesten Neutralinozerfälle und den Neutrinomischungswinkeln. Wir zeigen diese Beziehungen auf Baumgraphenniveau und für die Zweikörperzerfälle chi_1^0 -> l^\pm W^\mp auch in nächsthöherer Ordnung, da nur die volle Einschleifenkorrektur das erwartete Ergebnis liefert. Im Anhang werden die zwei für diese Arbeit erzeugten Programme MaCoR und CNNDecays vorgestellt. Während MaCoR die Berechnung von Massenmatrizen und Kopplungen in den besagten Modellen erlaubt, wurde mit CNNDecays die numerische Auswertung der Einschleifenrechnungen vorgenommen.