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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

A search for strong gravity effects with the ATLAS experiment

Moeller, Victoria January 2013 (has links)
No description available.
62

Models and Constraints for New Physics at the Energy, Intensity, and Cosmic Frontiers

Barello, Gregory 27 October 2016 (has links)
The modern era of particle physics is driven by experimental anomalies. Experimental efforts have become increasingly diverse and are producing enormous volumes of data. In such a highly data-driven scientific environment theoretical models are necessary to understand this data and to help inform the development of new experimental approaches. In this dissertation I present two significant contributions to this effort relevant to the energy, intensity, and cosmic frontiers of modern particle physics research. Part 1 of this dissertation discusses methods to understand modern dark matter direct detection results. In particular I present an analysis under the hypothesis of inelastic dark matter, which supposes that dark matter must scatter inelastically, i.e. that it must gain or loose mass during a collision with atomic nuclei. This hypothesis is attractive because it can alleviate otherwise contradictory results from a number of dark matter detection facilities. The main conclusion of this work is a presentation of the analytical tools, along with a mathematica package that can be used to run the analysis, and the discovery that there are regions of inelastic dark matter parameter space which are consistent with all current experimental results, and constraints. Part 2 of this dissertation discusses a phenomenon of modern interest called kinetic mixing which allows particles from the standard model to spontaneously transform into particles which experience a new, as of yet undiscovered, force. This phenomenon is relatively common and well motivated theoretically and has motivated significant experimental effort. In this work, I present an analysis of a general case of kinetic mixing, called nonabelian kinetic mixing. This work shows that, In general, kinetic mixing predicts the existence of a new particle and that, under certain conditions, this particle could be detected at modern particle colliders. Furthermore, the mass of this particle is related to the strength of kinetic mixing. This relationship suggests novel ways to constrain kinetic mixing parameter space, and if observed would provide a very striking indication that such a model is realized in nature.
63

Prospects for charged Higgs Boson searches at the Large Hadron Collider with early ATLAS data

Lane, Jenna Louise January 2010 (has links)
No description available.
64

Search for chargino and neutralino production using final states with two soft leptons in pp collisions at √s = 13 TeV / 重心系エネルギー 13 TeVの陽子陽子衝突における 2つの低運動量レプトンを用いたチャージーノとニュートラリーノの探索

Akatsuka, Shunichi 25 May 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22626号 / 理博第4615号 / 新制||理||1663(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)教授 中家 剛, 准教授 WENDELL Roger, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
65

φ photoproduction on the proton at Eγ=1.5-2.9 GeV / Eγ=1.5-2.9 GeVにおける陽子標的を用いたφ中間子光生成

Mizutani, Keigo 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20913号 / 理博第4365号 / 新制||理||1626(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)教授 永江 知文, 教授 鶴 剛, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
66

Rare Weak Decays of the Omega Baryon

Mommers, Cornelis Johannes Gerardus January 2022 (has links)
We study rare decays of the Omega baryon using SU(3) chiral perturbation theory, a successfuleffective field theory of quantum chromodynamics at low energies. At leading-order, we calculatethe branching fractions of the decay Ω− → Ξππ for all possible combinations of pions. For onechannel we find an order-of-magnitude discrepancy between theory and experiment. This tension isknown to exist in the non-relativistic limit, and we confirm that it remains when using a relativisticframework. Fairly independent of the values of our low energy constants we establish lower limitsfor the branching fractions, which reaffirm the gap between theory and experiment. A possibleexplanation for the gap is that the ∆I = 1/2 rule does not hold for nonleptonic Omega decays.If this were the case, fully differential distributions would be crucial to improving the theory.Here, as a baseline we present the conservative result based on the ∆I = 1/2 rule. Furthermore,at next-to-leading order we calculate the decay Ω− → Ξ0µ−νµ. We show that fully differentialdistributions will provide access to low-energy constants needed in the axial-vector transitions froma decuplet to octet baryon. The data for these rare three-body Omega decays are scarce (fullydifferential data are nonexistent), and we recommend that they be remeasured at running andupcoming experiments, such as BESIII, Belle-II, PANDA and LHCb.
67

Calcul Ab-initio de propriétés de résonances hadroniques légères / Ab-initio determination of light hadronic resonance properties

Frison, Julien 13 December 2012 (has links)
Il est établi depuis maintenant 40 ans que l'interaction nucléaire forte peut être décrite par la Chromodynamique Quantique (QCD). Le confinement des quarks dans cette théorie masque cependant ses degrés de liberté élémentaires dans les processus de basse énergie, qui doivent être calculés non-perturbativement. La QCD sur réseau est à ce jour la seule méthode permettant de mener à bien de tels calculs, et arrive dorénavant à maturité. Cependant, et alors que le spectre des hadrons stables est calculée avec précision, l'étude des désintégrations reste délicate. Nous présentons ici l'application du formalisme de Lüscher au calcul des propriétés de résonances se désintégrant sous l'interaction forte, ainsi qu'un calcul avec précision de la largeur de désintégration dans le cas particulier du meson rho. / It has been established for now 40 years that the strong nuclear interaction can be described by Quantum Chromodynamics (QCD). However, the confinement of quarks in this theory hides its elementary degrees of freedom in low-energy processes, which have to be computed non-pertubatively. Lattice QCD is, to date, the only method allowing to go through such a computation, and is now reaching maturity. However, although the spectrum of stable hadrons is computed with precision, the study of decays is still delicate. We hereby present the application of Lüscher's formalism to the study of strong-decaying resonance properties, along with a precise computation of the decay width in the particular case of the rho meson.
68

Search for S=+1 exotic baryon in [gamma]p--]K⁺K⁻[pi]⁺(n)

Guo, Lei, January 1900 (has links)
Thesis (Ph. D. in Physics)--Vanderbilt University, May 2004. / Title from title screen. Includes bibliographical references.
69

Fotoprodução difrativa do bóson de Higgs em colisões ultraperiféricas

Silveira, Gustavo Gil da January 2011 (has links)
das partículas elementares ainda é um método a ser estabelecido na Física de Partículas, o que poderia ser confirmado com a descoberta do bóson de Higgs. Após diversas propostas para mecanismos de produção, este bóson ainda não foi observado experimentalmente, sendo sua detecção esperada no Grande Colisor de Hádrons. Esta tese propõe um mecanismo de produção central exclusiva difrativa do bóson de Higgs pela fotoprodução, inspirado na abordagem do grupo de Durham para a produção deste bóson por meio da Troca Dupla de Pomerons. A ideia empregada neste mecanismo é combinar as vantagens encontradas na proposta do grupo de Durham com aquelas observadas nas Colisões Ultraperiféricas. O mecanismo de fotoprodução envolve a produção do bóson de Higgs no subprocesso p em alta energia por meio da Troca Dupla de Pomerons, onde a interação difrativa ocorre entre o dipolo de cor proveniente da flutuação do fóton inicial e o conteúdo platônico do próton. Como a massa do bóson de Higgs determina a escala dura da interação, é possível empregar a Cromodinâmica Quântica perturbativa e modelar a interação pela troca de glúons no canal t. Esse mecanismo permite introduzir o vértice de fusão de glúons para a produção do bóson de Higgs, o qual é dominante para a produção do bóson de Higgs em um largo intervalo de massa. Ademais, introduz-se parâmetros fenomenológicos para suprimir a radiação de glúons, bem como predizer corretamente a seção de choque de produção incluindo a Probabilidade de Sobrevivência da Lacuna de Rapidez. Com isso, aplica-se este modelo de interação p em Colisões Ultraperiféricas entre prótons e núcleos usando a Aproximação de Fóton Equivalente para o fluxo de fótons. A seção de choque de produção do bóson de Higgs é estimada para as energias do Tevatron e do LHC, comparando nossas predições com outras obtidas em diferentes propostas na literatura. Além disso, a distribuição em rapidez do bóson de Higgs é estudada, mostrando a centralidade da produção. Como resultado, obtém-se uma taxa de eventos em colisões pp da mesma ordem daquela estimada pelo grupo de Durham, na faixa de 1−6 femtobarn. Contudo, efetuando-se uma análise para inserção da Probabilidade de Sobrevivência da Lacuna de Rapidez no mecanismo de fotoprodução, os resultados se tornam competitivos com aqueles previstos pelos mecanismos de produção eletromagnética e de Troca Dupla de Pomerons, mostrando a fotoprodução difrativa como um meio promissor para a detecção do bóson de Higgs no LHC. Como resultado desta abordagem, as predições para a seção de choque em processos pA demonstra um incremento significativo em relação `as predições anteriores, estimando a seção de choque em colisões pPb da ordem de 1 picobarn. Este resultado é duas ordens de grandeza maior que em colisões pp, contudo a luminosidade e o tempo de operação com colisões pPb será muito menor que em colisões pp. Ainda assim, os eventos serão muito limpos, livres de interações superpostas que ocorrem em alta luminosidades na operação em colisões pp. / After several years of scientific development, the mass generation mechanism for elementary particles is still to be established in particle physics, which would be confirmed with the discovery of a Higgs boson. After many proposals for the production mechanisms, this boson has not yet been observed experimentally, and its detection at the Large Hadron Collider is expected. Here I propose a mechanism of central exclusive diffractive production of the Higgs boson by photoproduction, inspired by the approach of the Durham group for Higgs boson production by Double Pomeron Exchange. The idea employed in this mechanism is to combine the advantages found in the proposal of the Durham group, and those related to ultraperipheral collisions. The photoproduction mechanism involves Higgs boson production in the p subprocess at high energy by Double Pomeron Exchange, where the diffractive interaction occurs between the color dipole resulting from the fluctuation of the initial photon, and the parton content of the proton. As the Higgs boson mass determines the hard scale of the interaction, it is possible to apply perturbative Quantum Chromodynamics, and to describe the interaction by the exchange of gluons in the t-channel. This mechanism allows the introduction of the gluon fusion vertex for Higgs boson production, which is the leading mechanism for a wide range of masses. Moreover, phenomenological parameters are introduced to suppress gluon radiation, and correctly predict the production cross section including the rapidity gaps survival probability. Thus, this mechanism is applied to the p subprocess in ultraperipheral collisions between protons and nuclei using the Equivalent Photon Approximation for the photon flux. The cross section is estimated for Higgs boson production at the Tevatron and LHC energies, comparing these predictions to those from previous work. The Higgs boson rapidity distribution is also predicted to show the production centrality. As a result, the event rate in pp collisions is found to be of the same order as that estimated by the Durham group, in the range 1−6 femtobarn. However, evaluating an analysis to include the rapidity gap survival probability in the photoproduction mechanism, the results become competitive with those predicted by the electromagnetic and Double Pomeron Exchange mechanisms, showing the diffractive photoproduction to be a promising production channel for Higgs boson detection at the LHC. The predictions for the cross section in pA processes show a significant enhancement in comparison to previous estimates, resulting in a cross section for pPb collisions of the order of 1 picobarn. This is two orders of magnitude higher than in pp collisions, however both the luminosity and the running time with pPb collisions will be much lower than in pp ones. Nevertheless the events are going to be very clean, free of the pile-up present in high luminosities pp runnings.
70

Difração em colisões hadrônicas altamente energéticas

Machado, Mairon Melo January 2011 (has links)
Apresento as investigações realizadas durante estes quatro anos de doutorado no Grupo de Fenomenologia de Partículas de Altas Energias (GFPAE). Foi desenvolvido um estudo teórico/fenomenológico baseado em QCD perturbativa para processos difrativos em colisões hadrônicas e nucleares, considerando diferentes estados finais como observáveis. Este estudo tem como ponto principal a aplicação das chamadas correções de múltiplos espalhamentos de Pomerons no modelo de Ingelman-Schlein, e desta forma, fazer predições para a taxa de produção difrativa de vários tipos de partículas. Temos como ponto inicial o estudo dos eventos de espalhamento profundamente inelástico (DIS), onde a colisão lépton-próton permite estudar o conteúdo de pártons na estrutura interna dos nucleons. Estes processos são verificados no colisor HERA, dando excelentes informações sobre a subestrutura do próton. No caso de colisões hadrônicas, existe uma ampla variedade de partículas de interesse no estado final, e neste trabalho, apresento resultados para a produção difrativa de quarks pesados, quarkonia e o bóson de Higgs. O estudo fenomenológico desses processos é fundamental para entendermos como os hádrons são constituídos, além de como podemos descrever o Pomeron (partícula virtual portadora dos números quânticos do vácuo), servindo também como base para os experimentos desenvolverem seus aparatos e formas de medidas. Os processos difrativos possuem um sinal de fácil detecção no experimento, tendo como principal característica a verificação de uma região do detector onde nenhuma partícula ´e encontrada, região esta chamada lacuna de rapidez. O formalismo de Ingelman-Schlein (IS) é considerado para estudar o processo difrativo. Nele, o Pomeron ´e o responsável pela origem dessa lacuna, com o mesmo possuindo subestrutura. Desta forma, utilizo uma recente função para a distribuição de pártons no Pomeron, bem como o fator de probabilidade de sobrevivência da lacuna de rapidez (correções de múltiplos espalhamentos). Realizamos então estimativas teóricas para a taxa de produção difrativa de J/ , _, c¯c, b¯b e Higgs em colisões hadrônicas, com energias de centro de massa ps para o Large Hadron Collidr (LHC) de ps = 14 TeV, sendo que também foi realizado o estudo de produção de quarks pesados para colisões nucleares, no caso Chumbo-Chumbo (Pb-Pb) e Cálcio-Cálcio (Ca-Ca), com energias de psPb−Pb = 5.5 TeV e psCa−Ca = 6.3 TeV respectivamente, para os processos de difração simples e central. Os resultados obtidos são os primeiros na literatura a considerar a aplicação do modelo Ingelman-Schlein com correções para os observáveis citados em energias de LHC. As estimativas para a razão difrativa de produção de tais observáveis servem como uma ferramenta teórica para futura verificação e comparação com os dados a serem extraídos do colisor LHC, tendo como consequência a confirmação da validade do formalismo empregado para processos de difração dura (escala típica maior que 1 GeV) na região de altas energias. / An theoretical/phenomenological study was developed based on perturbative QCD for diffractive processes in nuclear and hadronic collisions, considering different final states as observables. This study had as main goal the application of the Pomeron Multiple Scattering corrections to the Ingelman-Schlein model, and in this way, obtaining predictions for the rate of diffractive production for several produced particles. We begin studying events of Deep Inelastic Scattering (DIS), where the lepton-proton collisions allow to verify the parton content of inner structure of the nucleons. These processes are currently studied at HERA collider, giving excelent information about the proton substructure. In the hadronic collisions, there is a huge variety of particles that can be of interest in the final state, and in this work we present results for the diffractive production of heavy quarks, quarkonia and Higgs boson. The phenomenological study of these processes is fundamental to understand how the hadrons are constituted and how we can describe the Pomeron (a virtual particle that carries the vacuum quantum numbers), being as well as a baseline to the that experiments develop their apparatus and measurements. The diffractive processes have a signal easy to be detected in the experiment, with the main characteristic being the verification of a region in the detector where low multiplicity of particles is found, this called rapidity gap. The Ingelman-Schlein (IS) formalism is considered to study the diffractive process. In this formalism, the Pomeron is responsible by the gap, with this particle having substructure. In this content, recent parton distribution functions for the Pomeron are considered, as well as the gap survival probability factor (multiple scattering corrections) are taken into account. Theoretical estimates are made for the rates of diffractive production of J/ , , c¯c, b¯b and Higgs in hadronic collisions, for the center-of-mass energy ps = 14 TeV that is the LHC energy. A study of single and central diffraction heavy quarks production in nuclear collisions was made for Lead-Lead (Pb-Pb) and Calcium-Calcium (Ca-Ca) collisions, both for LHC energies. The results obtained consider the Ingelman-Schlein application with corrections for the referred observables in the LHC energies. The estimations for the diffractive ratio for the production of these observables could be a theoretical tool for future investigations and comparison to experimental data, testing the validity of the formalism considered for hard diffraction processes (high momentum) in the high energy region.

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