The current state of supersymmetric models of elementary particle physics is reviewed. Full calculations of the differential cross sections for the production of squarks and gluinos are performed, and the results folded with parton distributions to give total cross sections for pp and pp processes. The gluino production rate is used together with an analysis of its decay, taking proper account of the transverse momentum distribution of the decay products, to derive limits on the gluino mass from existing beam dump experiments; this limit is rather weak, typically mg > 3 GeV (the exact results depend on the details of the supersymmetric model). The production of squarks and sleptons in ep processes is considered, allowing for gaugino-Higgsino mixing, and the prospects for using these processes to extract information about the gaugino-Higgsino mixing parameters are discussed. Finally we consider the production of squarks or sleptons in association with a photino; although of order of ϰ³ in perturbation theory, this process has a characteristic signature and may be where squarks or sleptons are first discovered if they are too heavy to be pair produced at LEP.

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Howard Baer, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains xiii, 132 pages. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-24Bitstream added on 2014-06-13T21:03:31Z : No. of bitstreams: 1 senisejunior_cr_dr_ift.pdf: 712685 bytes, checksum: 85898bebce02636a9c79fbd037306fe2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A ação efetiva e o potencial efetivo são objetos fundamentais no estudo de quebra de simetrias. Em teorias de campo supersimétricas, o cálculo destes objetos propicia uma ferramenta para a análise de como a supersimetria é quebrada, e a relação desta quebra com outras simetrias, como a simetria R. Desta forma, o estudo de correções radiativas para a ação efetiva e o potencial efetivo em modelos que realizam a quebra de supersimetria, tal como o modelo de O’Raifeartaigh e suas generalizações, é de extrema importância quando deseja-se estudar o efeito das correções quânticas para o potencial clássico destes modelos e como estas correções modificam suas características clássicas. Desenvolver métodos de somar as contribuições de uma determinada classe de diagramas de Feynman para estes modelos é fundamental para a obtenção de resultados de caráter não perturbativo. Para o estudo de processos supersimétricos, tais métodos de ressoma podem ser desenvolvidos utilizando um formalismo claro, compacto e elegante, que é o formalismo de supercampos. Neste formalismo, os diagramas de Feynman e, assim, as correções radiativas, são calculados utilizando-se as técnicas de cálculo no super-espaço, que reduz drasticamente a quantidade de diagramas a serem calculados em um determinado processo / The effective action and the effective potential are fundamental objects in the study of symmetries breaking. In supersymmetric field theories, the calculation of these objects provides a tool for the analysis of how supersymmetry is broken, and the relation of these breaking with other symmetries, such asR symmetry. In this way, the study of radiactive corrections for the effective action and the effective potential in models which accomplish the supersymmetry breaking, such as the O’Raifeartaigh model and its generalizations, is of extreme importance when one wishes to study the effect of quantum corrections for the classical potential of these modelsandhowthese corrections modifyitsclassical features. Developing methods tosumup the contributions of a determined class of Feynman diagrams for these models is fundamental to obtain results of nonperturbative character. For the study of supersymmetric processes, such ressumation methods can be developed using a clear, compact and elegant formalism, known as the superfield formalism. In this formalism, the Feynman diagrams and, henceforth, the radiactive corrections, are calculated using the techniques of superspace calculus, which drastically reduce the amount of diagrams to be calculated in a determined process

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Wong Chun Wing. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. [166]-169). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

One of the most popular extensions of the SM is Supersymmetry (SUSY). It is a symmetry relating fermions and bosons and also the only feasible extension to the symmetries of spacetime. With SUSY it is then possible to explain some of the open questions left by the SM while at the same time opening the possibility of gauge unification at a high scale. SUSY theories require the addition of new particles, in particular an extra Higgs doublet and at least as many new scalars as fermions in the SM. Much in the same way that the Higgs boson breaks SU (2)L symmetry, these new scalars can break any symmetry for which they carry a charge through spontaneous symmetry breaking. Let us assume there is a local minimum of the potential that reproduces the correct phenomenol- ogy for a parameter point of a given model. By exploring whether there are other deeper minima with VEVs that break symmetries we want to conserve, like SU (3)C or U (1)EM , it is possible to exclude regions of parameter space where that happens. The local minimum with the correct phenomenology might still be metastable, so it is also necessary to calculate the probability of tunneling between minima. In this work we propose and apply a framework to constrain the parameter space of models with many scalars through the minimization of the one-loop eff e potential and the calculation of tunneling times at zero and non zero temperature.After a brief discussion about the shortcomings of the SM and an introduction of the basics of SUSY, we introduce the theory and numerical methods needed for a successful vacuum stability analysis. We then present Vevacious, a public code where we have implemented our proposed framework. Afterwards we go on to analyze three interesting examples. For the constrained MSSM (CMSSM) we explore the existence of charge- and color- breaking (CCB) minima and see how it constraints the phenomenological relevant region of its parameter space at T = 0. We show that the regions reproducing the correct Higgs mass and the correct relic density for dark matter all overlap with regions suffering from deeper CCB minima. Inspired by the results for the CMSSM, we then consider the natural MSSM and check the region of parameter space consistent with the correct Higgs mass against CCB minima at T /= 0. We find that regions of parameter space with CCB minima overlap significantly with that reproducing the correct Higgs mass. When thermal eff are considered the majority of such points are then found to have a desired symmetry breaking minimum with very low survival probability. In both these studies we find that analytical conditions presented in the literature fail in dis- criminating regions of parameter space with CCB minima. We also present a way of adapting our framework so that it runs quickly enough for use with parameter fit studies. Lastly we show a different example of using vacuum stability in a phenomenological study. For the BLSSM we investigate the violation of R-parity through sneutrino VEVs and where in parameter space does this happen. We find that previous analyses in literature fail to identify regions with R-parity conservation by comparing their results to our full numerical analysis. / Eine der populärsten Erweiterungen des SM ist die Supersymmetrie (SUSY). Dies ist eine Symmetrie, die Bosonen und Fermionen in Beziehung setzt und auch die einzige machbare Erweiterung der Raumzeitsymmetrien. SUSY kann einige offene Fragen des SM erklären und eröffnet die Möglichkeit einer Vereinheitlichung der Eichwechselwirkungen bei einer hohen Skala. Supersymmetrische Theorien erfordern das Hinzufügen neuer Teilchen, insbesondere eines zusätzlichen Higgs-Dubletts und zumindest eines Skalars für jedes Fermion im SM. So wie im SM das Higgs-Boson die SU (2)L-Symmetrie bricht, können diese neuen Skalare jede Symmetrie, deren Ladung sie tragen, spontan brechen. Angenommen, es gibt ein lokales Minimum des Potentials, das die korrekte Phänomenologie für einen Parameterraumpunkt eines Modells erzeugt: Durch die Suche nach anderen tieferen Minima mit Vakuumerwartungswerten, die gewünschte Symmetrien wie SU (3) oder U (1)EM brechen, ist es möglich Parameterraumpunkte, in denen dies passiert, auszuschliessen. Das lokale Minimum mit der korrekten Phänomenologie kann immernoch metastabil sein, weshalb es auch notwendig ist, die Tunnelwahrscheinlichkeit zwischen zwei Minima zu berechnen. In dieser Arbeit legen wir eine Prozedur vor und wenden sie an, um den Parameterraum von Modellen mit vielen Skalaren durch die Minimierung des effektiven Ein-Schleifen-Potentials und durch die Berechnung seiner Lebensdauer sowohl bei T = 0 und bei T /= 0 einzuschränken. Nach einer kurzen Diskussion der Unzulänglichkeiten des SM und Einführung der Grundlagen von SUSY erläutern wir die Theorie und die die nötigen numerischen Methoden für eine erfolgreiche Analyse der Vakuumstabilitaet. Danach präsentieren wir Vevacious, ein öffentliches Programmpaket, in das wir unsere Prozedur implementiert haben. Daraufhin analysieren wir drei interessante Beispiele. Für das Constrained MSSM (CMSSM) untersuchen wir die die Existenz von Minima, in denen die Farb- oder elektrische Ladung nicht erhalten ist (CCB-Minima), und wie dessen phänomenologisch relevante Region des Parameter- raums dadurch bei T = 0 eingeschränkt wird. Wir zeigen, dass die Regionen, die die korrekte Higgsmasse und die richtige Relikt-Dichte für die Dunkle Materie reproduzieren, mit Regionen, die tiefere CCB-Minima aufweisen, überlappen. Inspiriert durch die Ergebnisse für das CMSSM betrachten wir dann das Natural MSSM und prüfen die Parameterraumregion mit der korrekten Higgsmasse auf CCB-Minima bei T /= 0.Wir finden, dass die Region des Parameterraums mit CCB-Minima deutlich mit denen mit einer korrekten Higgsmasse überlappt. Bei Berücksichtigung von thermalen Effekten hat ein Großteil der bei T = 0 langlebigen Punkte ein gewünschtes symmetriebrechendes Minimum mit einer sehr geringen Überlebenswahrscheinlichkeit bei T /= 0. In beiden Studien finden wir, dass die analytischen Bedingungen, die bisher in der Literatur präsentiert wurden, nicht ausreichen, um Bereiche des Parameterraums mit CCB-Minima auszuweisen. Wir präsentieren einen Weg, unsere Prozedur für die Nutzung in Parameterraum-Fit-Studien zu beschleunigen. Zuletzt zeigen wir ein weiteres Beispiel. Für das BLSSM untersuchen wir die Verletzung der R-Parität durch Sneutrino- VEVs und in welchen Parameterraumbereichen dies geschieht. Wir stellen durch Vergleich mit unserer kompletten numerischen Analyse heraus, dass frühere Analysen in der Literatur darin fehlschlagen, diese Bereiche mit Erhaltung der R-Parität zu identifizieren.