13 research outputs found

    Leptogenesis and Type I See-Saw Mechanism in the Out-of-equilibrium Quantum Field Theory

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    Um dos problemas mais importantes que precisa ser resolvido, tanto pela f√≠sica de part√≠culas como pela cosmologia, √© a exist√™ncia de assimetria bari√īnica. Entre os cen√°rios mais atrativos para a gera√ß√£o din√Ęmica da assimetria bari√īnica (Bariog√™nese) encontra- se a denominada Leptog√™nese. Nesse cen√°rio, cria-se uma assimetria lept√īnica que ser√° convertida em assimetria bari√īnica por processos n√£o perturbativos mediados por sphalerons. Na realiza√ß√£o mais simples da Leptog√™nese, que ser√° estudada nesta disserta√ß√£o, neutrinos pesados de m√£o direita, produzidos termicamente, decaem violando CP, gerando um assimetria lept√īnica nesses decaimentos. O principal atrativo deste cen√°rio √© que conecta duas escalas aparentemente diferentes: a escala da gera√ß√£o de assimetria lept√īnica e a escala das massas e oscila√ß√Ķes dos neutrinos ativos mediante o mecanismo de See-Saw. O estudo usual da Leptog√™nese utiliza equa√ß√Ķes de Boltzmann para determinar a evolu√ß√£o temporal da assimetria. Por√©m, a equa√ß√£o de Boltzmann √© uma equa√ß√£o semicl√°ssica, dado que envolve, por um lado, uma fun√ß√£o cl√°ssica no espa√ßo de fases, a fun√ß√£o de distribui√ß√£o, mas, por outro, os termos de colis√£o envolvem quantidades obtidas na teoria qu√Ęntica de campos √† temperatura nula. Em particular, a formula√ß√£o de Boltzmann n√£o permite descrever fen√īmenos qu√Ęnticos como oscila√ß√Ķes coerentes e efeitos de deco√™rencia e interfer√™ncia. Uma descri√ß√£o qu√Ęntica completa da evolu√ß√£o da assimetria lept√īnica na leptog√™nese deve, de fato, ser obtida no contexto da teoria qu√Ęntica de campos fora do equil√≠brio t√©rmico. O formalismo de Schwinger-Keldysh permite realizar isso. Nesta disserta√ß√£o descreveremos a leptog√™nese no formalismo de Schwinger-Keldysh para o caso em que s√£o adicionados ao espectro de part√≠culas do Modelo Padr√£o tr√™s neutrinos de m√£o direita, sem fazer qualquer suposi√ß√£o sobre a hierarquia de massas.One of the most important problems that is needed to solve by the Elementary Particle Physics as well as by the Cosmology is the existence of baryonic asymmetry. Among the most attractive scenarios of dynamic generation of baryonic asymmetry (Baryogenesis) is the so-called Leptogenesis. In that scenario, a leptonic asymmetry is treated in such a way that it will be converted in baryonic asymmetry by non-perturbative processes mediated by sphalerons. In the simplest realization of Leptogenesis, that will be studied in this disertation, heavy right-handed neutrinos, produzed thermally, decay violating CP generating a leptonic asymmetry in these decays. The principal attractive of this scenario is that it connects two apparently different scales, the scale of leptonic asymmetry generation and the scale of masses and oscillations of the active neutrinos through the See-Saw mechanism. The usual study of the leptogenesis uses Boltzmann equations in order to determine the temporal evolution of the asymmetry. However, the Boltzmann equation is a semiclassical equations, since, on one side, it is formulated for a classical function in phases space, the distribution function, but, on the other hand, the collision term involves quantities obtained in the Quantum Field Theory at zero temperature. In particular, Boltzmann formulation does not allow to describe quantum phenomena such coherent oscillations and effects of decoherence and interference. Indeed, a proper quantum description of the evolution of the leptonic asymmetry must be obtained in the context of the Non-Equilibrium Quantum Field Theory. The Schwinger-Keldysh formalism allows to perform this. In this dissertation, leptogenesis is described using the Schwinger-Keldysh formalism for the case in which there are three right-handed neutrinos without a definite mass hierarchy

    Neutrinos Massivos: Consequências fenomenológicas e cosmológicas

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    The XX century witnessed the quantum and relativistic revolutions in physics. The development of these two theories, namely, Quantum Mechanics and Relativity, was the inception of many crucial discoveries and technological advances. Among them, one stands out due to its uniqueness, the neutrino discovery. However, several neutrino properties are still obscure. Neutrinos are the only fundamental particles whose nature is currently unknown. Such fermions can either be different from their antiparticles, i.e., Dirac fermions, or be their own antiparticles, that is, Majorana fermions. On the other hand, the smallness of neutrino masses is a problem seemingly related to the neutrino nature; thus, as essential task consists in addressing the phenomenologically viable models in both cases. Furthermore, it is important to search for other physical process in which the neutrino nature may manifest through different experimental signatures. A rather difficult but promising method corresponds to the detection of the cosmic neutrino background, viz. neutrinos which are relics from the Big Bang. Previous works have shown that detection rates for Dirac and Majorana neutrinos can give different results. Nevertheless, this distinction was obtained considering the Standard Model framework only. Therefore, it is important to understand the consequences of having Non-Standard Interactions contributing to the detection of neutrinos from the cosmic background. Another remarkable relic predicted by Cosmology is the unidentified Dark Matter, composing ~25% of the Universe. All searches regarding the Weakly Interacting Massive Particle, one of the principal candidates for Dark Matter, have given negative results; this has compelled experiments to increase their sensitivity. Notwithstanding, neutrinos may stand in the way of such experimental searches given that they may constitute an irreducible background. In this thesis, we will address these three different phenomena, neutrino mass models, detection of the cosmic neutrino background and the neutrino background in Dark Matter searches, by considering the different characteristics in each case. In the study of neutrino mass models, we will consider models for both Majorana and Dirac neutrinos; specifically, we will probe the neutrinophilic two-Higgs-doublet model. Regarding the detection of relic neutrinos, we will analyse the consequences of the existence of the beyond Standard Model physics in the capture rate by tritium. Finally, we will scrutinize the impact of neutrinos in Direct Detection WIMP searches, by considering Standard Model plus additional interactions in the form of simplified models.Ao longo do s√©culo XX testemunhamos as revolu√ß√Ķes qu√Ęntica e relativista que aconteceram na F√≠sica. O desenvolvimento da Mec√Ęnica qu√Ęntica e da teoria da relatividade foi o prel√ļdio de in√ļmeras descobertas e avan√ßos tecnol√≥gicos fundamentais; em particular, a descoberta dos neutrinos. No entanto, a sua total compreens√£o ainda √© um mist√©rio para a f√≠sica de part√≠culas. Entendidos como part√≠culas fermi√īnicas fundamentais, os neutrinos possuem sua natureza desconhecida. Podendo ser diferentes de suas antipart√≠culas, denominadas f√©rmions de Dirac, ou tamb√©m podendo ser as suas pr√≥prias antipart√≠cula, sendo conhecidas como f√©rmions de Majorana. Por outro lado, o valor de sua massa continua sendo um problema em aberto, supostamente relacionado √† sua natureza. Portanto, √© importante estudarmos modelos fenomenol√≥gicos vi√°veis para as duas naturezas poss√≠ves dos neutrinos. Al√©m disso, √© necess√°rio procurar outros processos f√≠sicos cujos resultados experimentais sejam distintos de acordo com a natureza do neutrino. Um m√©todo bastante dif√≠cil, mas promissor, corresponde √† detec√ß√£o do fundo de neutrinos c√≥smicos, isto √©, os neutrinos rel√≠quia do Big Bang. An√°lises pr√©vias mostraram que as taxas de detec√ß√£o para neutrinos de Dirac e de Majorana resultam em valores distintos. Por√©m, este resultado foi obtido supondo como base o Modelo Padr√£o; assim, √© crucial entender as poss√≠veis consequ√™ncias da exist√™ncia de intera√ß√Ķes desconhecidas na detec√ß√£o dos neutrinos da radia√ß√£o c√≥smica de fundo. Outra rel√≠quia not√°vel prevista pela Cosmologia √© a desconhecida Mat√©ria Escura, que comp√Ķe ~25% do Universo. Todas as buscas por WIMPs (do ingl√™s Weakly Interactive Massive Particles), um dos principais candidatos a Mat√©ria Escura, tem dado resultados negativos. Isto tem for√ßado a cria√ß√£o de experimentos cada vez mais sens√≠veis. Contudo, os neutrinos poder√£o ser um obst√°culo nessas buscas experimentais, pois estes convertir-se-√£o em um fundo irredut√≠vel. Na presente tese, abordaremos estes tr√™s fen√īmenos diferentes, modelos de massa para os neutrinos, a detec√ß√£o do fundo de neutrinos c√≥smicos e o fundo de neutrinos em experimentos de detec√ß√£o direta de Mat√©ria Escura, considerando as distintas caracter√≠sticas em cada caso. No estudo dos modelos de massa para os neutrinos consideraremos modelos para neutrinos de Majorana e Dirac; exploraremos modelos neutrinof√≠licos com dois dubletos de Higgs. Enquanto √† detec√ß√£o dos neutrinos rel√≠quia, analisaremos as consequ√™ncias da presen√ßa de f√≠sica al√©m do Modelo Padr√£o na taxa de captura pelo tr√≠tio. Finalmente, examinaremos o impacto dos neutrinos em experimentos de detec√ß√£o direta de WIMPs, supondo as intera√ß√Ķes do Modelo Padr√£o junto com intera√ß√Ķes adicionais na forma de modelos simplificados

    Neutrinos Massivos: Consequências fenomenológicas e cosmológicas

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    The XX century witnessed the quantum and relativistic revolutions in physics. The development of these two theories, namely, Quantum Mechanics and Relativity, was the inception of many crucial discoveries and technological advances. Among them, one stands out due to its uniqueness, the neutrino discovery. However, several neutrino properties are still obscure. Neutrinos are the only fundamental particles whose nature is currently unknown. Such fermions can either be different from their antiparticles, i.e., Dirac fermions, or be their own antiparticles, that is, Majorana fermions. On the other hand, the smallness of neutrino masses is a problem seemingly related to the neutrino nature; thus, as essential task consists in addressing the phenomenologically viable models in both cases. Furthermore, it is important to search for other physical process in which the neutrino nature may manifest through different experimental signatures. A rather difficult but promising method corresponds to the detection of the cosmic neutrino background, viz. neutrinos which are relics from the Big Bang. Previous works have shown that detection rates for Dirac and Majorana neutrinos can give different results. Nevertheless, this distinction was obtained considering the Standard Model framework only. Therefore, it is important to understand the consequences of having Non-Standard Interactions contributing to the detection of neutrinos from the cosmic background. Another remarkable relic predicted by Cosmology is the unidentified Dark Matter, composing ~25% of the Universe. All searches regarding the Weakly Interacting Massive Particle, one of the principal candidates for Dark Matter, have given negative results; this has compelled experiments to increase their sensitivity. Notwithstanding, neutrinos may stand in the way of such experimental searches given that they may constitute an irreducible background. In this thesis, we will address these three different phenomena, neutrino mass models, detection of the cosmic neutrino background and the neutrino background in Dark Matter searches, by considering the different characteristics in each case. In the study of neutrino mass models, we will consider models for both Majorana and Dirac neutrinos; specifically, we will probe the neutrinophilic two-Higgs-doublet model. Regarding the detection of relic neutrinos, we will analyse the consequences of the existence of the beyond Standard Model physics in the capture rate by tritium. Finally, we will scrutinize the impact of neutrinos in Direct Detection WIMP searches, by considering Standard Model plus additional interactions in the form of simplified models.Ao longo do s√©culo XX testemunhamos as revolu√ß√Ķes qu√Ęntica e relativista que aconteceram na F√≠sica. O desenvolvimento da Mec√Ęnica qu√Ęntica e da teoria da relatividade foi o prel√ļdio de in√ļmeras descobertas e avan√ßos tecnol√≥gicos fundamentais; em particular, a descoberta dos neutrinos. No entanto, a sua total compreens√£o ainda √© um mist√©rio para a f√≠sica de part√≠culas. Entendidos como part√≠culas fermi√īnicas fundamentais, os neutrinos possuem sua natureza desconhecida. Podendo ser diferentes de suas antipart√≠culas, denominadas f√©rmions de Dirac, ou tamb√©m podendo ser as suas pr√≥prias antipart√≠cula, sendo conhecidas como f√©rmions de Majorana. Por outro lado, o valor de sua massa continua sendo um problema em aberto, supostamente relacionado √† sua natureza. Portanto, √© importante estudarmos modelos fenomenol√≥gicos vi√°veis para as duas naturezas poss√≠ves dos neutrinos. Al√©m disso, √© necess√°rio procurar outros processos f√≠sicos cujos resultados experimentais sejam distintos de acordo com a natureza do neutrino. Um m√©todo bastante dif√≠cil, mas promissor, corresponde √† detec√ß√£o do fundo de neutrinos c√≥smicos, isto √©, os neutrinos rel√≠quia do Big Bang. An√°lises pr√©vias mostraram que as taxas de detec√ß√£o para neutrinos de Dirac e de Majorana resultam em valores distintos. Por√©m, este resultado foi obtido supondo como base o Modelo Padr√£o; assim, √© crucial entender as poss√≠veis consequ√™ncias da exist√™ncia de intera√ß√Ķes desconhecidas na detec√ß√£o dos neutrinos da radia√ß√£o c√≥smica de fundo. Outra rel√≠quia not√°vel prevista pela Cosmologia √© a desconhecida Mat√©ria Escura, que comp√Ķe ~25% do Universo. Todas as buscas por WIMPs (do ingl√™s Weakly Interactive Massive Particles), um dos principais candidatos a Mat√©ria Escura, tem dado resultados negativos. Isto tem for√ßado a cria√ß√£o de experimentos cada vez mais sens√≠veis. Contudo, os neutrinos poder√£o ser um obst√°culo nessas buscas experimentais, pois estes convertir-se-√£o em um fundo irredut√≠vel. Na presente tese, abordaremos estes tr√™s fen√īmenos diferentes, modelos de massa para os neutrinos, a detec√ß√£o do fundo de neutrinos c√≥smicos e o fundo de neutrinos em experimentos de detec√ß√£o direta de Mat√©ria Escura, considerando as distintas caracter√≠sticas em cada caso. No estudo dos modelos de massa para os neutrinos consideraremos modelos para neutrinos de Majorana e Dirac; exploraremos modelos neutrinof√≠licos com dois dubletos de Higgs. Enquanto √† detec√ß√£o dos neutrinos rel√≠quia, analisaremos as consequ√™ncias da presen√ßa de f√≠sica al√©m do Modelo Padr√£o na taxa de captura pelo tr√≠tio. Finalmente, examinaremos o impacto dos neutrinos em experimentos de detec√ß√£o direta de WIMPs, supondo as intera√ß√Ķes do Modelo Padr√£o junto com intera√ß√Ķes adicionais na forma de modelos simplificados

    Highly-parallelized simulation of a pixelated LArTPC on a GPU

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    The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10310^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

    The DUNE Far Detector Vertical Drift Technology, Technical Design Report

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    International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

    Highly-parallelized simulation of a pixelated LArTPC on a GPU