京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19219号 / 理博第4111号 / 新制||理||1592(附属図書館) / 32218 / 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

No description available.

In this report, we aim to assess the sensitivity and 5$\sigma$ discovery potential of IceCube, the largest neutrino observatory on Earth, and compare it with prior findings. Our thesis will focus on a point source analysis, exploring the energy and declination dependencies, with particular emphasis on high-energy neutrinos. The primary objective is to establish the feasibility of detecting 5$\sigma$ evidence supporting the hypothesis that blazars serve as sources of neutrinos in the Southern sky, as suggested in a recent publication. Our findings indicate a substantial improvement in both discovery potential and sensitivity for the Southern sky in recent years. Furthermore, we highlight the increasing significance of investigating the origins of high-energy neutrinos in the Southern sky.

No description available.

The Daya Bay experiment has determined the last unknown mixing angle $theta_{13}$. This thesis describes the layout of the experiment and the detector design. The analysis presented in the thesis covered the water attenuation, spent fuel neutrino and electron anti-neutrino spectrum. Other physics analysis and impact to future experiments are also discussed. / Ph. D.

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.

Existierende Neutrinoteleskope sind für den Nachweis von Neutrinos aus astrophysikalischen Quellen mit Energien im TeV Bereich optimiert. Aufgrund der geringen Flüsse und Wirkungsquerschnitte wurden bislang keine extraterrestrischen hochenergetischen Neutrinos beobachtet. Erst die im Bau befindlichen kubikkilometer-großen Cherenkov-Neutrinodetektoren werden das notwendige Volumen haben, um diese nachzuweisen. Für Neutrinos aus Wechselwirkungen der kosmischen Strahlung im EeV-Bereich mit dem kosmischen Mikrowellenhintergrund wird dennoch nicht mehr als ein Ereignis im Jahr erwartet. Nachweisvolumen in der Größenordnung von 100 km^3 sind notwendig, um den Fluß dieser Neutrinos zu bestimmen und die vorhergesagten Wirkungsquerschnitte zu überprüfen. Alternative Meßtechniken sind erforderlich, um einen Detektor dieses Ausmaßes zu realisieren. Eine vielversprechende Idee ist die Erfassung akustischer Wellen aus den in der Neutrinowechselwirkung erzeugten hadronischen Kaskaden. Aufgrund der höheren Signalstärke und der großen Schalldämpfungslängen ist die Eisdecke des Südpols dem Wasser der Ozeane als Medium vorzuziehen. Zunächst sind jedoch geeignete Sensoren, eine Überprüfung der thermo-akustischen Schallerzeugung und Kenntnisse der akustischen Eigenschaften des Eises von Nöten. In einer theoretischen Ableitung konnte die Äquivalenz der Mechanismen der Erzeugung akustischer Wellen durch thermo-elastische Anregung in Flüßigkeiten und isotropen Festkörpern gezeigt werden. Einer Analyse des existierenden Wissensstandes folgte die Simulation eines kombinierten Cherenkov-Radiowellen-Ultraschall-Detektors. Für den Einsatz im Eis wurden spezielle akustische Sensoren entwickelt und zur Erfassung der Schallemission von intensiven Protonen- und Laserstrahlen eingesetzt. Darauf aufbauend wurde ein akustische Sender- und Empfänger-Aufbau entwickelt, mit dem Ziel, die Ultraschalleigenschaften des südpolaren Eises in-situ zu untersuchen. Die Ergebnisse dieser ersten Bemühungen werden in dieser Arbeit vorgestellt. / Current neutrino telescopes are designed to detect neutrinos with energies in the TeV range. Due to the low fluxes and small cross sections, no high energy neutrinos of extraterrestrial origin have been observed so far. Only the Cherenkov neutrino detectors on the km^3 scale that are currently under construction will have the necessary volume to observe these rare interactions. Yet, for neutrinos from interactions of the ultra-high energy cosmic at EeV energies rays with the ambient cosmic microwave background, event rates of only one per year are expected. To measure the flux and verify the predicted cross sections of these cosmogenic neutrinos, an observed volume of around 100 km^3 will be necessary, that will not be feasible with existing detection techniques. Alternative methods are required to build a detector on these scales. One promising idea is to record the acoustic waves generated in cascades following the neutrino interaction. Higher amplitudes of the sonic signal and the large absorption length of sound favour South Polar ice instead of sea water as a medium. For an estimate of the potential of such a detector, suitable acoustic sensors, a verification of the model of thermo-acoustic sound generation and a determination of the acoustic properties of the ice are necessary. In a theoretical derivation the mechanism of thermo-elastic excitation of acoustic waves was shown to be equivalent for isotropic solids and liquids. A detailed analysis of the existing knowledge and a simulation study of a hybrid optical-radio-acoustic detector have been performed. Ultrasonic sensors dedicated to in-ice application were developed and have been used to record acoustic signals from intense proton and laser beams. Based on this, the hitherto largest array of acoustic sensors and transmitters was devised and implemented, with the aim to study the ultrasonic properties of the South Polar ice in-situ. Results from all of these first efforts are presented.

Nach der Entdeckung eines diffusen Flusses hochenergetischer astrophysikalischer Neutrinos durch das IceCube South Pole Neutrino Observatory im Jahr 2013 sind die Quellen, die für den Großteil dieser Emission verantwortlich sind, immer noch unbekannt. Blazare, jene AGN mit einem relativistischen Jet, der auf die Erde zeigt, gelten als Hauptkandidaten für die Beschleunigung der kosmischen Strahlung und die Produktion hochenergetischer Neutrinos. Diese Doktorarbeit ist motiviert durch den Nachweis des Gammastrahlen-Blazers TXS 0506+056 in räumlicher Koinzidenz mit dem Neutrino IceCube-170922A. 
In dieser Arbeit präsentiere ich die Ergebnisse einer detaillierten Gammastrahlenanalyse des Blazars TXS 0506+056 über 9,6 Jahre Fermi-LAT-Beobachtungen. Die Quelle ist stark variabel im Gammastrahlenband zur Ankunftszeit des Neutrinos IceCube-170922A, was auf eine Neutrino-Gammastrahlen-Verbindung hindeutet. Die Quelle wird jedoch während eines zusätzlichen niederenergetischen Neutrinosignals, das 2014/15 von Ice-Cube in Archivdaten von derselben Quelle entdeckt wurde, in einem niedrigen Zustand beobachtet. In dieser Arbeit wurde ein zweiter Gammastrahlen-Blazar GB6 J1040+0617 in räumlicher und zeitlicher Übereinstimmung mit dem hochenergetischen Neutrino-Ereignis IceCube-141209A gefunden, während er eine erhöhte Aktivität im Gammastrahlen- und im optischen Band zeigt. Eine zweite Suche nach Blazar-Gegenstücken zu hochenergetischen Neutrinos erfolgt durch Echtzeit-Follow-up von mehr als 60 IceCube-Alerts mit dem Fermi-LAT. Der kräftige Blazar PKS 1502+106, der zusammen mit dem Ereignis IceCube-190730A gefunden wurde, stellt einen herausragenden wissenschaftlichen Fall dar. Schließlich wird eine Studie zum Vergleich der durchschnittlichen Gammastrahlenemission der potenziellen Neutrino-Gegenstücke mit der gesamten Stichprobe von Gammastrahlen-Blazaren vorgestellt. Die Ergebnisse zeigen mögliche Hinweise auf eine Korrelation zwischen Neutrino- und Gammastrahlen-Energieflüssen. / After the discovery of a diffuse flux of high-energy astrophysical neutrinos by the IceCube South Pole Neutrino Observatory in 2013, the sources responsible for the majority of this emission are still unknown. Blazars, those AGN with a relativistic jet pointing towards Earth, are considered prime candidates for cosmic-ray acceleration and the production of high-energy neutrinos. This thesis work is motivated by the detection of the flaring gamma-ray blazar TXS 0506+056 in spatial and temporal coincidence with the neutrino event IceCube-170922A, that represented a milestone for the new field of multi-messenger astronomy. In this thesis, I present the results of a detailed gamma-ray analysis of the blazar TXS 0506+056 over 9.6 years of Fermi-LAT observations. The source shows strong flux variability in the gamma-ray band at the arrival of IceCube-170922A, indicating a neutrino gamma-ray connection, while is observed in a lowstate during an additional lower-energy neutrino signal detected from the same source by IceCube in 2014/15 in archival data. This puzzling behaviour has motivated further studies on the blazar sources coincident with single high-energy neutrinos. In this thesis, a second gamma-ray blazar GB6 J1040+0617, is found in spatial and temporal coincidence with the high-energy neutrino event IceCube-141209A while showing enhanced activity in the gamma-ray and optical bands. A second search for blazar counterparts to high-energy neutrinos is done through realtime follow-up of more than 60 IceCube alerts with the Fermi-LAT. The powerful blazar PKS 1502+106 found coincident with the event IceCube-190730A represents an outstanding science case. Lastly, a study to compare the average gamma-ray emission of the potential neutrino counterparts to the entire sample of gamma-ray blazars is presented. The results show possible indications of correlation between neutrino and gamma-ray energy fluxes.

Orientador: Marcelo Moraes Guzzo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-01T21:05:54Z (GMT). No. of bitstreams: 1 Zavanin_EduardoMarcio_D.pdf: 12290577 bytes, checksum: e37b2af24ec03321ad993ebd98fbc0dc (MD5) Previous issue date: 2017 / Resumo: O objetivo desse trabalho é estudar um mecanismo alternativo à hipótese de neutrino estéril para a solução das anomalias dos antineutrinos de reatores, da anomalia do Gálio e da anomalia dos aceleradores. Vamos também entender como encaixar esse mecanismo na teoria da física de partículas através de interações não padrão. Além disso, vamos estudar o duplo decaimento beta sem a emissão de neutrinos e colocar vínculos para a massa efetiva de Majorana. Não obstante, vamos entender os limites que o experimento ECHo fornecerá para medidas direta da massa dos neutrinos / Abstract: The objective of this work is the study of an alternative mechanism, that is not the hypothesized sterile neutrino, to solve the reactor anti-neutrino anomaly, the Gallium anomaly and the LSND anomaly. We will also understand how to fit this mechanism in the theory of particle physics through non standard interactions. In addition, we will study the neutrino-less double beta decay and set constraints to the effective Majorana neutrino mass. Furthermore we will understand the limits that the ECHo experiment will provide for direct measurements of the neutrino mass / Doutorado / Física / Doutor em Ciências / 2013/02518-7 / 1189631/2013 / FAPESP / CAPES