Identifying what makes up the Dark Matter is a long-standing problem to which the abundance of gravitational and cosmological evidence fails to answer. Indirect detection techniques have the aim to unveil the nature of Dark Matter by catching and identifying the products of potential decays and/or annihilations. The work exposed in this thesis is in line with this strategy and has for common thread the quest for line(-like) features in the extraterrestrial fluxes of gamma-rays and neutrinos. The motivation behind this specific interest is that, due to the absence of astrophysical counterparts beyond the GeV scale, these features constitute the ultimate probes (also called “smoking guns”) of the existence of Dark Matter.The thesis is organized in three Parts, the first of which is an introduction to the different facets of the Dark Matter conundrum and why it is not a trivial issue. The works involving gamma-ray line considerations are gathered in Part II, and those exclusively focusing on neutrino lines in Part III.Part II focuses on the effective field theory of Dark Matter decay, first in the context of millicharged particles decaying to gamma-ray lines, and then in the context of (neutral and millicharged) Dark Matter decays involving the simultaneous emission of gamma-ray and neutrino lines. In both cases, the simultaneous emission of cosmic rays is unavoidable and the decays are constrained in a multi-messenger fashion. The complementarity of the results obtained is used to derive model-independent constraints on the Dark Matter lifetime, and shows the possibility to exclude or distinguishsome specific scenarios on the basis of an explicit experimental conjecture.After an introduction to the neutrino detection principles and to the operation of the IceCube detector, Part III focuses on two careful searches for spectral features in the neutrino spectrum. The main goal behind these analyses, conducted in two different regions of the energy spectrum but using the same likelihood ratio procedure, is to popularize dedicated energy distribution studies by showing their ability to reach sensitivity levels comparable to—sometimes even going beyond—those obtained with angular distribution studies or even in the context of gamma-ray line searches. / Option Physique du Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Orientador: Marcelo Moraes Guzzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T07:13:46Z (GMT). No. of bitstreams: 1 Costa_RafaelNobertoAlmeidada_M.pdf: 2184656 bytes, checksum: 96104bbac452f3b0ec1bab401b55bf0a (MD5) Previous issue date: 2014 / Resumo: Apresentamos neste trabalho um review descrevendo a oscilações de neutrinos quando é levado em conta a violação da simetria de carga paridade (CP). Por conta disso abordaremos a origem da violação de CP no Modelo Padrão das Partículas Elementares, desde a sua descoberta no sistema dos mésons káons neutros (K°) ,até a sua inclusão dentro do Modelo Padrão, a qual foi desenvolvida por Kobayashi e Maskawa. Depois de entendermos a violação de CP passamos a tratar das oscilações de neutrinos e como esta violação é incluída no modelo. Abordamos o modelo utilizando os dados mais recentes dos parâmetros para as oscilações de neutrinos, incluindo a recente medição do ângulo de mistura ?13. Utilizando estes dados e os resultados obtidos a partir do modelo de oscilações de neutrinos inferimos um limite para a fase de violação de CP, dado por nós como sendo ?CP= 19 ^{+19°}_{-9°} com 1? de C.L. / Abstract: In this work was make a review describing the neutrino oscillations when is taken in account the charge parity symmetry violation (CP). Because of that we will approach the origin of CP violation in Standard Model of Elementary Particles, since its discovery in the neutral kaons meson system (K°), until its inclusion within the Standard Model, made by Kobayashi and Maskawa. After we understand the CP violation we treat the neutrino oscillations and how this violation is included in the model. We approach the model using the most recent data of the parameters from neutrino oscillations, including the recent data measured to the mixing angle ?13. Utilizing this data, and the data obtained from the model of neutrino oscillation, we infer a limit to the CP violation phase, given by us as being ?CP= 19^{+19°}_{-9°} with 1? of C.L. / Mestrado / Física / Mestre em Física

The IceCube Neutrino Observatory has sensitivity to MeV electron antineutrinos from core-collapse supernovae through an excess of the detection rate over the background. Wavelength-shifting sensors have the potential to greatly increase photon collection making it a promising candidate for improving the measurement of the supernova neutrino light curve in IceCube-Gen2. For high-energy neutrino reconstruction, the competing effect of increased photon collection and the broader time distribution necessitate detailed simulations to determine the impact. In this thesis, we investigate the sensitivity gain caused by wavelength shifters in a future IceCube-Gen2 detector regarding the detection of faint modulations of the supernova neutrino lightcurve. Furthermore, we lay the groundwork for a future high-energy reconstruction through the implementation and integration of wavelength-shifting sensors into the IceCube simulation framework.

No description available.

In this thesis, we review the basics of phenomenology in particle physics at neutrino beam dump experiments and hadron colliders. We then consider the phenomenology of various new particles, with masses between 1 MeV and 1 TeV, at the intensity and energy frontiers. We perform sensitivity analyses for physics beyond the standard model at particle colliders (LEP and LHC) and a number of past and future neutrino beam dump experiments (SHiP, DUNE, LSND, MicroBooNE, MiniBooNE and SBND). In particular, we motivate searches for new heavy neutral leptons in single photon events at neutrino and collider experiments (and also via supernova cooling), millicharged particles in single electron events at neutrino experiments, lepton flavor violating scalars via standard model induced mixed flavor neutrino trident production at neutrino experiments, and colored scalar doublets at colliders in events with many jets, soft leptons and low missing energy. In the process, we set novel new bounds on the parameters of these theories and propose powerful new searches that can be performed. We also motivate the construction of a new detector at the LHC called milliQan, and perform a full Geant4 simulation to calculate its projected sensitivity for millicharged particles. The milliQan experiment has since been approved and is currently undergoing construction. / Thesis / Doctor of Philosophy (PhD) / In this thesis, we review the basics of particle physics at neutrino experiments and particle colliders. We then motivate and develop key searches that can be performed to look for new particles at a series of existing and future experiments. We focus on new particles with masses between the electron mass and 1000 times the proton mass. The many searches we consider involve looking for processes that produce a single ray of light, a single electron, a pair of oppositely charged "electron-like" events, new collider signatures, and/or modifications of star explosions. In the process, we set novel new bounds on many theories. We also motivate the construction of a new detector at the Large Hadron Collider called milliQan, and perform a full simulation to assess its future performance. The milliQan experiment has since been approved and is currently undergoing construction.

The search for the neutrinoless double beta (0nbb) decay is one of the most active fields in modern particle physics. This process is not allowed within the Standard Model and its observation would imply lepton number violation and would lead to the Majorana nature of neutrinos. The experimentally observed quantity is the half-life of the decay, which can be connected to the effective Majorana neutrino mass via nuclear matrix elements. The latter can only be determined theoretically and are currently affected by large uncertainties. To reduce these uncertainties one can investigate the well established two-neutrino double beta (2nbb) decay into the ground and excited states of the daughter isotope. These similar processes are allowed within the Standard Model. In this dissertation, the search for 2nbb decays into excited states is performed in Pd-110, Pd-102 and Ge-76. Three gamma spectroscopy setups at the Felsenkeller (Germany), HADES (Belgium) and LNGS (Italy) underground laboratories are used to search for the transitions in Pd-110 and Pd-102. No signal is observed leading to lower half-live bounds (90% C.I.) of 2.9e20 yr, 3.9e20 yr and 2.9e20 yr for the 0/2nbb 2p1, 0p1 and 2p2 transitions in Pd-110 and 7.9e18 yr, 9.2e18 yr and 1.5e19 yr for the 0/2nbb 2p1, 0p1 and 2p2 transitions in Pd-102, respectively. This is a factor of 1.3 to 3 improvement compared to previous limits. The data of Phase I (Nov 2011 - May 2013) of the 0nbb decay experiment GERDA at LNGS is used to search for excited state transitions in Ge-76. The analysis is based on coincidences between two detectors and finds no signal. Lower half-life limits (90 % C.L.) of 1.6e23 yr, 3.7e23 yr and 2.3e23 yr are obtained for the 2nbb 2p1, 0p1 and 2p2 transitions, respectively. These limits are more than two orders of magnitude larger than previous ones and could exclude many old matrix element calculations. In addition to the excited state searches, important measurements and improvements for GERDA Phase II upgrades are performed within this dissertation. 30 new BEGe detectors are characterized for their surface and active volume properties which is an essential ingredient for all future physics analyses in GERDA. These precision measurements reduce the systematic uncertainty of the active volume to a subdominant level. In extension to this, a new model for simulating pulse shapes of n+ electrode surface events is developed. With this model it is demonstrated that the dominant background of K-42 on the detector surfaces can be suppressed by a factor of 145 with an A/E pulse shape cut in Phase II. A further suppression of background is obtained by a liquid argon scintillation light veto. With newly developed Monte Carlo simulations, including the optical scintillation photons, it is demonstrated that Tl-208 in the detectors holders can be suppressed by a factor of 134. K-42 homogeneously distributed in the LAr can be suppressed with this veto in combination with pulse shape cuts by a factor of 170 for BEGe detectors. The characterization measurements and the developed simulation tools presented within this dissertation will help to enhance the sensitivity for all 0/2nbb decay modes and will allow to construct an improved background model in GERDA Phase II. / Die Suche nach dem neutrinolosen Doppelbetazerfall (0nbb) ist eines der aktivsten Felder der modernen Teilchenphysik. Der Zerfall setzt die Verletzung der Leptonenzahl voraus und hätte die Majorananatur des Neutrinos zur Folge. Die durch eine Beobachtung bestimmbare Halbwertszeit des Zerfalls ermöglicht, über ein nukleares Matrixelement, Zugang zur effektiven Majorananeutrinomasse. Die größten Unsicherheiten gehen dabei auf das Matrixelement zurück, welches nur durch verschiedene, teilweise stark voneinander abweichende theoretische Modelle zugänglich ist. Eine Möglichkeit diese Unsicherheiten zu reduzieren bieten genaue Studien des im Standardmodel erlaubten neutrinobegleiteten Doppelbetazerfalls (2nbb) in angeregte Zustände des Tochterkerns. In dieser Dissertation wird der 2nbb-Zerfall der Nuklide Pd-110, Pd-102 und Ge-76 in angeregte Zustände untersucht. Die Untersuchungen von Pd-110 und Pd-102 wurden in drei umfangreichen Gammaspektroskopie-Experimenten in den Untergrundlaboren Felsenkeller (Deutschland), HADES (Belgien) und LNGS (Italien) durchgefürt. Es wurde kein Signal beobachtet und damit die weltweit besten unteren Grenzen für die Halbwertszeit dieser Zerfälle festgesetzt: 2,9e20 yr, 3,9e20 yr und 2,9e20 yr für die 0/2nbb 2p1, 0p1 und 2p2 Übergänge in Pd-110 and 7,9e18 yr, 9,2e18 yr und 1,5e19 yr für die 0/2nbb 2p1, 0p1 und 2p2 Übergänge in Pd-102 (90% C.I.). Dies ist eine 1,3 bis 3-fache Verbesserung gegenüber den vorher bekannten Grenzen. Die Untersuchung des 2nbb-Zerfalls in Ge-76 basiert auf Daten aus Phase I (Nov. 2011 - Mai 2013) des 0nbb-Zerfall Experiments GERDA. Mit der auf koinzidenten Ereignissen basierten Analyse konnte kein Signal beobachtet werden und folgende untere Grenzen für die Halbwertszeit der 2nbb 2p1, 0p1 und 2p2 Übergänge wurden festgelegt: 1,6e23 yr, 3,7e23 yr und 2,3e23 (90% C.L.). Diese 100-fache Verbesserung gegenüber den bisher bekannten Grenzen widerlegt eine Vielzahl älterer, zur Verfügung stehender Matrixelemente. Zusätzlich wurden im Rahmen dieser Dissertation für die Erweiterungen des GERDA Experiments zur Phase II wichtige Messungen durchgeführt und Verbesserungen entwickelt. 30 neu produzierte BEGe Detektoren wurden hinsichtlich ihrer Oberflächeneigenschaften sowie ihrer aktiven Volumina charakterisiert. Diese Präzisisionsmessungen sind für alle zukünftigen Analysen in GERDA notwendig und erlauben die entsprechenden systematischen Unsicherheiten auf ein subdominantes Niveau zu reduzieren. Erweiternd wurde ein neues Model zur Beschreibung der n+ Elektrode entwickelt, welches erstmals erlaubt die Pulsform von Oberflächeninteraktionen zu simulieren. Mithilfe dieses Models konnte demonstriert werden, dass der in Oberflächeninteraktionen begründete und in GERDA dominante Messuntergrund von K-42 auf der Detektoroberfläche durch Pulsformanalyse um das 145-fache unterdrückt werden kann. Eine weitere Untergrundreduzierung wird durch ein Flüssigargon Szintillationsveto erreicht. Im Rahmen dieser Arbeit wurden vorhandene Monte Carlo Simulationen um den Transport von optischen Photonen erweitert und die 134-fache Unterdrückung des Tl-208 Untergrundes demonstriert. Die Ergebnisse dieser Arbeit helfen eine deutliche Sensitivitätsverbesserung für die zuküntige Suche nach dem 0/2nbb-Zerfall zu erzielen und erlauben die Erstellung eines präziseren Untergrundmodels in GERDA Phase II.

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

Há várias evidências experimentais da existência de matéria escura no universo. Apesar destas evidências, pouco se sabe sobre sua constituição, sabendo-se apenas que interage gravitacionalmente, mas não eletromagneticamente. Neste projeto, investigamos a possibilidade da matéria escura ser composta por partículas supermassivas e fortemente interagentes (Simpzillas). Para isto determinamos o sinal que deve ser deixado no telescópio IceCube por neutrinos resultantes de aniquilações de matéria escura no Sol. Após determinarmos o espectro de neutrinos no centro do Sol, simulamos sua propagação até a superfície, depois até a Terra e através da Terra até o detector. Comparamos então estes resultados com os fornecidos pelo IceCube. Esta comparação permite testar uma região do espaço de fase massa versus seção de choque previamente não-excluída por outros tipos de experiência que não telescópios de neutrinos. Como resultado, concluímos que partículas supermassivas e fortemente interagentes não podem constituir a matéria escura. / There are many experimental evidences for the existence of dark matter in the universe. Despite these evidences, there is no knowledge about its constitution other than the fact that it interacts gravitationally but not electromagnetically. In this project, we investigate the possibility that dark matter is composed of strongly interacting massive particles (Simpzillas). We determine the expected signal in the IceCube telescope from Simpzilla annihilation in the center of the Sun. We first determine the neutrino spectrum in the core of the Sun. We then simulate its propagation through both the Sun and Earth, and finally the rate of neutrinos at the detector. A comparison of these results to the ones published by the IceCube collaboration covers a large region of the yet not excluded regions of the mass versus cross-section phase space. As a result, the possibility of Simpzillas composing the dark matter is ruled out.

im Postscript-Format

Das IceCube-Experiment sucht nach astrophysikalischen, hochenergetischen Neutrinos, von deren Entdeckung man sich Antworten auf die seit mehr als 100 Jahren offene Frage nach dem Ursprung der kosmischen Strahlung erhofft. Zu diesem Zweck wurde ein kubikkilometergroßes Volumen tief im Antarktischen Eisschild mit optischen Sensoren instrumentiert, um die in Neutrinowechselwirkungen entstandene Cherenkov-Strahlung nachzuweisen.Diese Dissertation beschreibt eine Suche nach neutrinoinduzierten Teilchenschauern in Daten, die von April 2008 bis Mai 2009 während der Konstruktionsphase von IceCube aufgezeichnet wurden. Zu dieser Zeit war etwa die Hälfte der endgültigen Detektoranordnung in Betrieb. Das Ziel der Arbeit war die Entdeckung astrophysikalischer Neutrinos mit der Maßgabe, gleichzeitig eine Sensitivität für Neutrinos terrestrischen Ursprungs aufrecht zu erhalten. Beide Sorten von Neutrinos müssen von einem vielfach größeren Untergrund von atmosphärischen Myonen isoliert werden. Die Suche nach Teilchenschauern im Detektor bietet sich hierfür an, da diese Signatur einer Neutrinowechselwirkung eine gute Energierekonstruktion ermöglicht und sich qualitativ von der Signatur des Myonuntergrunds unterscheidet. Eine robuste Abschätzung des Myonuntergrunds wurde mittels Luftschauersimulationen gewonnen. Methoden wurden entwickelt, um Neutrinos und Myonen voneinander zu unterscheiden. Zwei verschiedene Ereignisselektionen wurden erstellt. Die erste zielt mit einer Energieschwelle von 2 TeV auf die Messung atmosphärischer Neutrinos ab und fand einen geringen Überschuss an Ereignissen der quantitativ gut mit atmosphärischen Neutrinos erklärt werden kann, jedoch nicht signifikant genug ist, um einen rein myonischen Ursprung auszuschließen. Die zweite Selektion war mit einer Energieschwelle von 100 TeV für astrophysikalische Neutrinos optimiert. Der gefundene Überschuss ist kompatibel mit einer stringenteren Flussmessung, die mit dem fertiggestellten IceCube Detektor gelang. / The IceCube experiment aims at the detection of an astrophysical high-energy neutrino flux from which answers are expected regarding the long standing question of the origin of cosmic rays. To this end, a cubic-kilometer volume deep in the glacial ice has been instrumented with digital optical sensors in order to record Cherenkov light emitted by charged secondary particles that are generated in neutrino interactions. This dissertation presents a search for neutrino-induced particle showers, also called cascades, in data taken between April 2008 and May 2009 during IceCube’s construction phase, when about 50% of the final configuration was deployed and operational. The goal of this analysis is the detection of the astrophysical diffuse neutrino flux while maintaining sensitivity to neutrinos originating from the Earth’s atmosphere. Both neutrino fluxes must be separated from a much more abundant background of muons created in cosmic-ray-induced air showers. Good energy reconstruction and a signature in the detector that is qualitatively different from the muon background make cascade searches very well-suited for this task. A robust estimate of this background has been obtained from air-shower simulations. Techniques were developed to isolate the neutrino flux from the atmospheric muon background. Two event selections were prepared. Firstly, a low-energy sample with an energy threshold of about 2 TeV aimed at the detection of atmospheric neutrinos. A small excess above atmospheric muons was found that can be explained well by atmospheric neutrinos but is not significant enough to rule out a muon-only hypothesis. Secondly, a high-energy sample with an energy threshold of about 100 TeV targeted astrophysical neutrinos. A 2.7 sigma excess over the expectation from atmospheric muons and neutrinos was found. It is compatible with ­more stringent flux estimates obtained by measurements with the completed IceCube detector.