The hunt for Dark Matter plays a truly critical role in contemporary physics. At both the largest and smallest scales, deep questions are being raised about the fundamental nature of the universe - questions that confirmation and then characterisation of particle dark matter will provide many answers to. This thesis presents some of the world's most sensitive searches to date for certain types of axion dark matter, axion-like particles, and two-neutrino double electron capture. These have been conducted using the Large Underground Xenon (LUX) experiment. Evidence for dark matter and physics beyond the Standard Model of particle physics is described in Chapter 1, while Chapter 2 gives an overview of proposed candidates for particle dark matter. The various experimental approaches being used to detect particle dark matter are presented in Chapter 3. Direct detection with time projection chambers plays a major role in this thesis, with particular interest in the LUX detector, that is described in its components and operations. Chapter 4 presents LUX direct searches for weakly interacting massive particles. Although I have contributed to these analyses, they are included for completeness only, as they are not part of my central work. The LUX collaboration's searches for axion dark matter and axion-like particle have delivered world-leading results on the axion-electron coupling constant. These results, that I personally led and which have been published in Physics Review Letters, are presented in Chapter 5, along with sensitivity studies, also led by me, made for the future LUX-ZEPLIN experiment. Finally, a search for two-neutrino double electron capture of 124Xe, that I performed using LUX data to extract a limit on the half life of the process, is presented in Chapter 6. Although being allowed by the Standard Model, two-neutrino double electron capture shares the matrix element calculation framework with the neutrinoless channel of the same process, becoming of great interest in the scope of neutrino physics. Conclusions follow and close the thesis.

The electroweak hierarchy problem is one of the most important puzzles of particle physics that remains without conclusive answer nowadays. One of the most recent new class of solutions to this problem is presented in this thesis, i.e., the cosmological relaxation of the electroweak scale. In this framework, we postulate the existence of a new particle, the relaxion, which drives the Higgs mass to values much smaller than the cutoff of the theory during inflation. As tools to develop this subject, this work presents a resume of chiral perturbation theory, the strong CP problem, axions and the eta prime particle. Finally, we will describe the most simple model of cosmological relaxation of the electroweak scale and the non-QCD model, where a new strong group SU(N) forms a condensate that interacts with the relaxion. / O problema da hierarquia eletrofraco é um dos enigmas mais importantes da física de partículas que continua sem uma solução conclusiva hoje em dia. Uma nova classe de soluções, dentre as mais recentes, para este problema é apresentado nessa dissertação, i.e., o relaxamento cosmológico da escala eletrofraca. Neste quadro, nós postulamos a existência de uma nova partícula, o relaxion, que conduz a massa do bóson de Higgs para valores muito menores que o cutoff da teoria durante a inflação. Como ferramentas para desenvolver este assunto, este trabalho apresenta um resumo de teoria de perturbação quiral, o problema CP forte, axions e a partícula eta prime. Finalmente, iremos descrever o modelo mais simples de relaxamento cosmológico da escala eletrofraca e o modelo sem-QCD, onde um novo grupo de interação forte SU(N) forma um condensado que interage com o relaxion.

It is shown in three examples that future cosmological data may allow us to constrain fundamental physics in interesting ways. The first example illustrates that correlations in the polarization of the cosmic microwave background may allow us to put the strongest limit yet on the mass of a particle, the graviton, at a level of m . 10−30 eV. In the second example, it is shown that observations of the correlations of temperature anisotropies and polarization of the cosmic microwave background may reveal hints for the realization of a class of string theoretic inflationary models that go by the name of axion monodromy inflation, or, rule them out. If the evidence for inflation strengthens substantially, just the requirement that inflation occurred may be used to constrain models of fundamental physics. The third example shows that a class of string compactifications that are commonly used in the context of string phenomenology cannot support inflation and might thus be ruled out by cosmology. For completeness, a review of the physics underlying the cosmic microwave background radiation is included and some analytical results for the signatures of primordial gravitational waves in the cosmic microwave background are given. / text

京都大学 / 新制・課程博士 / 博士(理学) / 甲第22993号 / 理博第4670号 / 新制||理||1670(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)准教授 吉岡 興一, 教授 田中 貴浩, 准教授 髙山 史宏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Astrophysical observations indicate the existence of dark matter through its gravitational interaction, but since its other interactions remain undetected, its particle nature is still unknown. There are several dark matter candidates, one being a hypothetical particle called axion that can have three types of non-gravitational couplings: electromagnetic, electric dipole moment (EDM), and gradient. This dissertation presents experimental approaches and axionlike dark matter search results from two table-top experiments: Cosmic Axion Spin Precession Experiment (CASPEr-electric) sensitive to EDM and gradient couplings, and Search for Halo Axions with Ferromagnetic Toroids (SHAFT) sensitive to electromagnetic coupling. CASPEr-electric is a resonant search for axionlike dark matter through the induced nuclear spin precession. The experimental approach is measuring nuclear magnetic resonance (NMR) of the heavy atom in a ferroelectric crystal. Experimental setup is characterized using pulsed NMR calibration measurements. Recorded search data that is sensitive to axionlike dark matter is analyzed by optimal filtering and then setting a detection threshold based on the histogram of power spectral density modeled as a Gaussian distribution. The candidates above the threshold are all rejected through statistical fluctuations and scan/re-scan measurements. CASPEr-electric places the upper bounds on the EDM and gradient couplings of axionlike dark matter in the Compton frequency range from 39.1 MHz to 40.2 MHz. SHAFT is a broadband search for axionlike dark matter through the induced oscillatory magnetic field. The resultant magnetic flux is measured with a precision magnetometer called superconducting quantum interference device (SQUID), coupled to a coil placed on the inner surface of a ferromagnetic toroid. After analyzing the search data, all candidates are rejected and SHAFT places a limit on electromagnetic coupling of axionlike dark matter between 3 kHz and 3 MHz Compton frequencies. Finally, coupling limits placed by CASPEr-electric and SHAFT are evaluated in the wider parameter space, and possible future directions that both experiments could take to improve their sensitivities to axionlike dark matter are discussed. / 2022-09-27T00:00:00Z

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18779号 / 理博第4037号 / 新制||理||1581(附属図書館) / 31730 / 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 川上 則雄, 教授 佐々 真一, 教授 前野 悦輝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

One of the major unsolved questions of modern physics is the nature of dark matter, whose existence is inferred from astronomical observations. There are numerous potential dark matter candidates: one strong contender is the axion. The axion was initially proposed to solve the strong CP problem of quantum chromodynamics but it was later realized that its properties make it simultaneously a good candidate for dark matter. Axions couple to the Standard Model in various ways. In this thesis, we describe experiments which exploit the axion coupling gd to the nuclear electric dipole moment (nEDM). In particular, in the presence of an external electric field, the axion perturbs the magnetization of an ensemble of nuclear spins due to this coupling. In the CASPEr-Electric experiment, the axion dark matter interacts with the nuclear spins of 207Pb and the effective electric field is provided by a ferroelectric crystal in which the 207Pb is embedded. CASPEr-Electric is a resonant search where axion dark matter would perturb the equilibrium magnetization of the 207Pb nuclear spin ensemble. The experiment is calibrated through pulsed nuclear magnetic resonance (NMR) experiments on the 207Pb nuclei. The first generation of the experiment demonstrated the feasibility of this method and established limits on the nEDM coupling in the mass range of 162-166 neV (Compton frequency 39-40 MHz). This thesis primarily focuses on the second generation of the CASPEr-Electric experiment, which probed axion dark matter at a lower frequency range of 4 - 5 MHz using superconducting quantum interference devices (SQUIDs). Our search established upper limits on the coupling for axion masses in the range 19.5-20.5 and 21.5-22 neV (4.6 - 5.0 and 5.2 - 5.3 MHz). The upper bound on the nEDM coupling is |gd| < 4 x 10-4, GeV-2 with 95 % confidence. / 2024-11-07T00:00:00Z

Topological insulators are materials with their electronic band structure in bulk resembling that of an ordinary insulator, but the surface states are metallic. These surface states are topologically protected, meaning that they are robust against impurities. The topological phenomena of three dimensional topological insulators can be expressed within topological field theories, predicting axion electrodynamics and the topological magnetoelectric effect. An experiment have been suggested to measure the topological phenomena. In this thesis, the underlying theory and details around the experiment are explained and more detailed derivations and expressions are provided.

Orientador: Prof. Dr. Alysson Fábio Ferrari / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2016. / Operadores contendo derivadas superiores não estão incluídos no Modelo Padrão Estendido (SME) e podem ter relevância na busca por uma teoria que opere na escala de Planck. Nessa tese de doutorado investigamos algumas consequências físicas no regime de baixas energias devido a violação de Lorentz (Lorentz violation, ou LV) gerada por operadores desse tipo. Começamos com um modelo constituído pelo campo fermiônico carregado e massivo , pelo campo do fóton A e pelo campo do tipo áxion (ALP ou axion-like-particle) . A LV aparece através dos acoplamentos não mínimos Fd e 5=b , onde d e b são os vetores constantes responsáveis pela introdução da LV. Assumimos que o campo fermiônico tem massa muito grande, e integramos a ação efetiva no campo do férmion, obtendo então como correção quântica de uma laço uma interação efetiva a baixa energia entre o campo do fóton e o campo do ALP, que resulta ser do mesmo tipo de interação que tem sido investigado em pesquisas experimentais atuais. Em seguida, estudamos outras consequências da interação Fd por meio correções quânticas de um laço, agora exclusivamente no setor de fóton. Mostramos que tal interação LV é responsável por gerar na ação efetiva operadores LV com derivadas superiores. Dentre as correções quânticas geradas consideramos a correção até primeira ordem no parâmetro LV d, juntamente com as correções não lineares de mais baixa ordem, e investigamos efeitos da LV na propagação de ondas eletromagnéticas em uma região contendo um campo magnético forte e constante. Por fim investigamos consequências físicas adicionais da interação Fd por meio das interações entre fontes externas intermediadas pelo campo eletromagnético, onde discutimos os principais fenômenos físicos que emergem dessa teoria e que não são contemplados na teoria de Maxwell usual. / Higher derivatives operators are not included in the Standard Model Extension (SME) and they can have relevance in the search by a theory which operates in the Planck energy scale. In this PhD thesis we investigate some physical consequences in the low energy regime due to LV which was generated by this kind of operators. We start with a model in the high energy regime that is constituted by the charged massive fermionic field , by the photon field A and by the axion-like-particle (ALP) field . The LV appear in our model due to the two couplings Fd and 5=b , where d and b are the constant vectors responsible for introducing the LV. We assume the fermion mass to be very high and we integrate the effective action in the fermion field, obtaining as one-loop quantum correction an effective interaction in the low energy regime between the photon field and ALP field, which we show to be of the same form as the one studied in current experimental searches. Then, we study other physical consequences of the interaction Fd through one-loop quantum corrections in the pure photon sector. We show that such LV interaction generates in the effective action Lorentz violating higher derivatives operators. Among the generated quantum corrections we consider the ones of the first order in the LV parameter d; together with the lowest order non-linear corrections, and we investigate the effects of the LV in the electromagnetic wave propagation in a region with a strong, constant magnetic field. To finish, we investigate additional physical consequences of the interaction Fd through interactions between external sources intermediated by the electromagnetic field, where we discuss the main physical phenomena that emerge of this theory which have no counterpart in Maxwell theory.

The lack of direct evidence for physics beyond the SM at the LHC has led some to reevaluate the need for such physics to solve the hierarchy problem. Instead, the notion that the SM, or something like it, is valid up to the Planck scale and that technical naturalness is sufficient for solving the hierarchy problem has been suggested. This thesis examines minimal extensions of the SM that address its phenomenological and theoretical shortcomings while avoiding new physics between the electroweak and Planck scales that introduces a hierarchy problem. This thesis first studies two issues with the vMSM - an extension of the SM by three right-handed neutrinos - and their possible solutions. The first issue is the tension between dark matter production in the nuMSM and constraints from the Lyman-alpha forest data. To avoid this tension, the vMSM is extended by a Higgs singlet &Phi; and neutrino dark matter is produced through the decays of &Phi; rather than through left-right neutrino mixing. It is shown that the hierarchical parameters of this model can arise from symmetries broken at or near the Planck scale for two specific examples: one in which &Phi; stabilizes the electroweak vacuum and one in which &Phi; is a light inflaton. The second issue pertains to Higgs &xi;-inflation. In the vMSM, a large non-minimal coupling &xi; of the Higgs to gravity gives inflation but leads to a possible violation of perturbative unitarity below the inflationary scale. A study of Higgs &xi;-inflation with M_h &simeq; 125-126 GeV, for which the Higgs self-coupling &lambda; runs to small values near the Planck scale, is carried out. It is shown that small &lambda; can significantly reduce &xi; required for inflation, but &xi; cannot be small enough to address the possible unitarity issue. For small &lambda;, a new region of Higgs &xi;-inflation with a large tensor-to-scalar ratio r that is consistent with BICEP2 is discovered. This thesis then studies the technical naturalness and cosmology of a model that addresses the strong CP problem. It is shown that a classically scale invariant DFSZ invisible a&xi;on model with a Peccei-Quinn scalar S, whose couplings to the SM are ultra-weak, can solve the strong CP problem and generate electroweak symmetry breaking via the Coleman-Weinberg mechanism. The ultra-weak couplings of S are natural due to an underlying appro&xi;mate shift symmetry. The model contains a light pseudo-Goldstone dilaton that can be consistent with cosmological bounds while the a&xi;on can be the dark matter of the universe. Finally, a summary of the thesis is presented and future research topics are suggested.