The discovery of the Higgs boson in the 8 TeV run of the LHC [1, 2] marks one of the most important milestones in particle physics. Its mass is already known rather precisely: mh = 125.09 ± 0.21 (stat.) ±0.11 (syst.) GeV [3], and the signal strength of various LHC searches has been found consistent with the SM predictions. While this completes the Standard Model (SM) particle-wise, several questions still remain open, for example: (i) Is it possible to include the SM in a grand unified theory where all gauge forces unify? (ii) Is there a particle physics explanation of the observed dark matter relic density? (iii) What causes the hierarchy in the fermion mass spectrum and why are neutrinos so much lighter than the other fermions? What causes the observed mixing patterns in the fermion sector? (iv) What stabilizes the Higgs mass at the electroweak scale? Supersymmetric model address several of these questions and consequently the search for supersymmetry (SUSY) is among the main priorities of the LHC collaborations. Up to now no significant sign for physics beyond SM has been found. The combination of the Higgs discovery with the (yet) unsuccessful searches has led to the introduction of a model class called ‘natural SUSY’ [4–15]. Here, the basic idea is to give electroweak-scale masses only to those SUSY particles giving a sizeable contribution to the mass of the Higgs boson, such that a too large tuning of parameters is avoided. All other particle masses are taken at the multi-TeV scale. In particular, masses of the order of a few hundred GeV up to about one TeV are assigned to the higgsinos (the partners of the Higgs bosons), the lightest stop (the partner of the top-quark) and, if the latter is mainly a left-stop, also to the light sbottom In addition the gluino and the heavier stop masses should also be close to at most a few TeV. Neutrino oscillation experiments confirm that at least two neutrinos have a non-zero mass. The exact mass generation mechanism for these particles is unknown, and both the SM and the MSSM remain agnostic on this topic. Although many ways to generate neutrino mass exist, perhaps the most popular one is the seesaw mechanism [16–21]. The main problem with the usual seesaw mechanisms lies on the difficulty in testing its validity. In general, if Yukawa couplings are sizeable, the seesaw relations require Majorana neutrino masses to be very large, such that the new heavy states cannot be produced at colliders. In contrast, if one requires the masses to be light, then the Yukawas need to be small, making production cross-sections and decay rates to vanish. A possible way out of this dilemma lies on what 3 is called the inverse seesaw [22], which is based on having specific structures on the mass matrix (generally motivated by symmetry arguments) to generate small neutrino masses. This, at the same time, allows Yukawa couplings to be large, and sterile masses to be light. We consider here a supersymmetric model where neutrino data are explained via a minimal inverse seesaw scenario where the gauge-singlet neutrinos have masses in the range O(keV) to O(100 GeV). We explore this with a parametrization built for the standard seesaw, and go to the limit where the inverse seesaw emerges, such that Yukawas and mixings become sizeable. Although non-SUSY versions of this scenario can solve the dark matter and matter-antimatter asymmetry problems [23–25], we shall make no claim on these issues in our model. In view of the naturalness arguments, we further assume that the higgsinos have masses of O(100 GeV), whereas the gaugino masses lie at the multi-TeV scale (see [26] for an example of such a scenario). In addition, we assume all squarks are heavy enough such that LHC bounds are avoided, and play no role in the phenomenology within this work1. In contrast we allow for fairly light sleptons and investigate the extent to which current LHC data can constrain such scenarios. This paper is organized as follows: in the next section we present the model. Section III summarizes the numerical tools used and gives an overview of the LHC analysis used for these investigations. In Section IV we present our findings for the two generic scenarios which differ in the nature of the lighest supersymmetric particle (LSP): a Higgsino LSP and a sneutrino LSP. In Section V we draw our conclusions. Appendices A and B give the complete formulae for the neutrino and sneutrino masses. / Tesis

Se presenta mediciones polarimétricas de fases geométricas generadas en la evolución de la polarización de fotones a lo largo de trayectorias no‐geodésicas en la esfera de Poincaré.El núcleo del arreglo polarimétrico consiste de siete placas retardadoras. Este arreglo permite realizar cualquier transformación unitaria del grupo SU(2) en el espacio de polarización. Haciendo uso de la invariancia gauge de las fases geométricas bajo transformaciones locales U(1), es posible anular la contribución dinámica a la fase total, con lo cual se logra que esta última coincida con la fase geométrica. Como la fase total es accesible a las mediciones experimentales, la fase geométrica se torna así también accesible a las mismas. Se demuestra que nuestro dispositivo es robusto frente a diversas perturbaciones que usualmente afectan arreglos interferométricos, ya que utilizamos un solo haz de fotones. Nuestro arreglo polarimétrico de muestra ser una herramienta sumamente versátil que podría ser utilizada para someter a prueba la robustez de las fases geométricas frente a varias fuentes de decoherencia. / Tesis

Orientador: Bruto Max Pimentel Escobar / Mestre

Neste trabalho é feito um estudo comparativo entre diferentes métodos de solução da equação do transporte de nêutrons aplicados ao problema de criticalidade da placa plana. São comparados os valores obtidos pelo método de Case e pelo método PN àqueles obtidos pelos recentemente desenvolvidos métodos LTPN e LTSN, cujo cálculo é feito pela primeira vez. / This work is a comparative study about different methods oi solution of the Neutron Transport Equation applied to the critical slab problem. Results obteined at the first time by the recently developed LTPN and LTSN Methods to the critical slab problem are compared to those obteined by Case's Method and PN Method.

En el presente trabajo el campo de neutrones producido por una fuente de neutrones de 241Am-Be es evaluado experimentalmente, debido que actualmente en el Perú no existe un laboratorio de Calibración de neutrones que preste servicios de calibración de equipos y detectores de neutrones térmicos. Además se describe los instrumentos y equipos utilizados en el proceso de detección de neutrones térmicos. La evaluación experimental se realiza en etapas, se usa varios elementos moderadores tales como parafina borada, polietileno y Cadmio a su vez se termalizan en diferentes geometrías como se muestran en la figuras 14, 15, 19 y 20. Mediante diferentes métodos tales como hojuelas Au197, CR-39 y TLD se obtienen flujos y dosis provenientes de la fuente isotópica, además mediante una serie de cálculos experimentales y teóricos (MCNP-4b) se determinan las características de la fuente isotópica Am-Be y del espectro gamma obtenido de un detector semiconductor de GeHP se puede determinar la energía gamma promedio. Se procede a realizar pruebas de reproducibilidad con las diferentes técnicas para obtener un mayor grado de precisión en los datos. Esta evaluación permite obtener datos para futuras calibraciones de equipos y/o detectores tales como CR-39, TLD y BF3 para monitoreo de personal expuesto a fuentes de neutrones provenientes de reactores nucleares, aceleradores lineales y fuentes portátiles así como para el monitoreo ambiental en caso de riesgo radiológico. Además se pretende con esta evaluación diseñar, construir, estudiar materiales para el blindaje, un sistema de irradiación de neutrones guardando todos los sistemas de seguridad que pide la AEIA. / Trabajo de suficiencia profesional

Neste trabalho é feito um estudo comparativo entre diferentes métodos de solução da equação do transporte de nêutrons aplicados ao problema de criticalidade da placa plana. São comparados os valores obtidos pelo método de Case e pelo método PN àqueles obtidos pelos recentemente desenvolvidos métodos LTPN e LTSN, cujo cálculo é feito pela primeira vez. / This work is a comparative study about different methods oi solution of the Neutron Transport Equation applied to the critical slab problem. Results obteined at the first time by the recently developed LTPN and LTSN Methods to the critical slab problem are compared to those obteined by Case's Method and PN Method.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2016. / Made available in DSpace on 2016-10-19T13:22:40Z (GMT). No. of bitstreams: 1 342538.pdf: 914685 bytes, checksum: e3056a236d2293ab499aa52a38b496c5 (MD5) Previous issue date: 2016 / Apresentamos seções de choque rotacionais para espalhamento de pósitrons de baixa energia por moléculas de H2 abaixo do limiar de formação de positrônio ( ). As seções de choque rotacionais foram calculadas na Aproximação Rotacional Adiabática a partir do cálculo a núcleo fixo realizado com o método Schwinger Multicanal. Realizamos a comparação com outros resultados teóricos similares e a partir destes verificamos que para a transição Ji=0 -> Jf=2 as seções de choque rotacionais são fortemente afetadas pela metodologia usada para modelar os efeitos de correlação-polarização.<br> / Abstract : We present rotational excitation cross sections for low energy scattering of positrons by H2, below positronium formation threshold ( ). The cross sections were computed from fixed-nuclei scattering amplitudes generated with the Schwinger multichannel method using the adiabatic rotational approximation. Comparison with other similar theoretical results shows that the magnitude of the cross section associated to the transition Ji=0 -> Jf=2 is strongly affected by the methodology used to model the correlation-polarization effects.

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Made available in DSpace on 2014-06-11T19:32:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-10-03Bitstream added on 2014-06-13T19:42:33Z : No. of bitstreams: 1 santos_as_dr_ift.pdf: 2147503 bytes, checksum: 5d62e5e2b0ada118a28a666128ee6e93 (MD5) / Modelosque preveem a existência de dimensões espaciais extras são estudados desde as primeiras décadas do século XX. São modelos que podem incorporar a gravitação à estrutura que descreve as demais interações e podem apresentar uma série de características interessantes como, por exemplo, candidatos à matéria escura. Nesse trabalho exploramos as consequências do modelo de Dimensões Extras Universais (UED) buscando pela produção de partículas de Kaluza-Klein cuja cadeia de decaimento leva à assinaturaµ±µ±+jatos+ET/ . O conjunto de dados analisados corresponde a uma luminosidade total integrada de 7,3 fb−1 coletada pelo detector DØ a partir de colisões próton-antipróton com energia de centro-de-massa de 1,96 TeV geradas pelo anel de colisão Tevatron do Fermilab. Uma vez que nenhum excesso foi observado nos dados, pode-se obter um limite inferior de 260 GeV para a escala de compactificaçãoR−1 do modelo. Este é o primeiro estudo a obter um limite direto para o modelo mínimo de UED / Models that predict the existence of extra spatial dimensions have been studied since the beginning of the 20th century. These models can incorporate gravity in the framework that describes the other interactions and they can present a number of interesting features such as a dark matter candidate. In this work, we explore the consequences of the Universal Extra Dimensions (UED) model by searching for the production of Kaluza-Klein particles whose decay chain leads to signatureµ±µ±+jets+ET/ . We employ the data set corresponding to an integrated luminosity of 7.3 fb−1, collected by the DØ detector at ap¯p collider at a center of mass energy of 1.96 TeV. Since no excess was observed in the data, we were able to set a lower limit on the compactification scale ofR−1> 260 GeV in the model. This is the first study to impose a direct limit on the minimal UED model

Orientador: Sérgio Ferraz Novaes / Coorientador: Pedro Galli Mercadante / Banca: Arthur Marques Moraes / Banca: Arthur Kós Antunes Maciel / Banca: Ricardo D'Elia Matheus / Banca: Leandro Salazar de Paula / Resumo: Modelosque preveem a existência de dimensões espaciais extras são estudados desde as primeiras décadas do século XX. São modelos que podem incorporar a gravitação à estrutura que descreve as demais interações e podem apresentar uma série de características interessantes como, por exemplo, candidatos à matéria escura. Nesse trabalho exploramos as consequências do modelo de Dimensões Extras Universais (UED) buscando pela produção de partículas de Kaluza-Klein cuja cadeia de decaimento leva à assinaturaµ±µ±+jatos+ET/ . O conjunto de dados analisados corresponde a uma luminosidade total integrada de 7,3 fb−1 coletada pelo detector DØ a partir de colisões próton-antipróton com energia de centro-de-massa de 1,96 TeV geradas pelo anel de colisão Tevatron do Fermilab. Uma vez que nenhum excesso foi observado nos dados, pode-se obter um limite inferior de 260 GeV para a escala de compactificaçãoR−1 do modelo. Este é o primeiro estudo a obter um limite direto para o modelo mínimo de UED / Abstract: Models that predict the existence of extra spatial dimensions have been studied since the beginning of the 20th century. These models can incorporate gravity in the framework that describes the other interactions and they can present a number of interesting features such as a dark matter candidate. In this work, we explore the consequences of the Universal Extra Dimensions (UED) model by searching for the production of Kaluza-Klein particles whose decay chain leads to signatureµ±µ±+jets+ET/ . We employ the data set corresponding to an integrated luminosity of 7.3 fb−1, collected by the DØ detector at ap¯p collider at a center of mass energy of 1.96 TeV. Since no excess was observed in the data, we were able to set a lower limit on the compactification scale ofR−1> 260 GeV in the model. This is the first study to impose a direct limit on the minimal UED model / Doutor