Aspects of supersymmetric field theories in four and six dimensions

PhDSupersymmetry is an important concept in modern high energy physics. It has found many applications in theoretical considerations of supersymmetric gauge theories as well as in phenomenological approaches to physics beyond the Standard Model. In this report we discuss some recent progress in supersymmetric eld theories in four and six dimensions. After introducing basic ideas and properties of supersymmetry we review the concept of scattering amplitudes in maximally supersymmetric theories in four dimensions before constructing a related framework in six dimensions. Here, the spinor helicity formalism and on-shell superspace were recently developed for six-dimensional gauge theories with (1,1) supersymmetry. We combine these two techniques with (generalised) unitarity, which is a powerful technique to calculate scattering amplitudes in any massless theory. As an application we calculate one-loop superamplitudes with four and ve external particles in the (1,1) theory and perform several consistency checks on our results. Within the area of phenomenological applications of supersymmetric gauge theories, we brie y review basic properties of supersymmetry breaking and gauge mediation in four dimensions. An important recent development has been the concept of theories with broken supersymmetry and metastable vacua. By using the advances of Seiberg duality, we examine a metastable N = 1 Macroscopic SO(N) SQCD model of Intriligator, Seiberg and Shih (ISS). We introduce various baryon and meson deformations, including multitrace operators. In this setup, direct fundamental messengers and the symmetric pseudomodulus messenger mediate supersymmetry breaking to a minimal supersymmetric Standard Model. We compute gaugino and sfermion masses and compare them for each deformation type. We also explore reducing the rank of the magneti

Direct Mediation and Metastable Supersymmetry Breaking for SO(10)

We examine a metastable $\mathcal{N}=1$ Macroscopic SO(N) SQCD model of Intriligator, Seiberg and Shih (ISS). We introduce various baryon and meson deformations, including multitrace operators and explore embedding an SO(10) parent of the standard model into two weakly gauged flavour sectors. Direct fundamental messengers and the symmetric pseudo-modulus messenger mediate SUSY breaking to the MSSM. Gaugino and sfermion masses are computed and compared for each deformation type. We also explore reducing the rank of the magnetic quark matrix of the ISS model and find an additional fundamental messenger.Comment: 43 pages, Latex. Version to appear in JHEP

(De)Constructing a Natural and Flavorful Supersymmetric Standard Model

Using the framework of deconstruction, we construct simple, weakly-coupled supersymmetric models that explain the Standard Model flavor hierarchy and produce a flavorful soft spectrum compatible with precision limits. Electroweak symmetry breaking is fully natural; the mu-term is dynamically generated with no B mu-problem and the Higgs mass is easily raised above LEP limits without reliance on large radiative corrections. These models possess the distinctive spectrum of superpartners characteristic of "effective supersymmetry": the third generation superpartners tend to be light, while the rest of the scalars are heavy.Comment: 36 pages, 4 figures ; v2: references added, expanded discussion of FCNC

Rare meson decays into very light neutralinos

We investigate the bounds on the mass of the lightest neutralino from rare meson decays within the MSSM with and without minimal flavor violation. We present explicit formulae for the two-body decays of mesons into light neutralinos and perform the first complete calculation of the loop-induced decays of kaons to pions and light neutralinos and B mesons to kaons and light neutralinos. We find that the supersymmetric branching ratios are strongly suppressed within the MSSM with minimal flavor violation, and that no bounds on the neutralino mass can be inferred from experimental data, i.e. a massless neutralino is allowed. The branching ratios for kaon and B meson decays into light neutralinos may, however, be enhanced when one allows for non-minimal flavor violation. We find new constraints on the MSSM parameter space for such scenarios and discuss prospects for future kaon and B meson experiments. Finally, we comment on the search for light neutralinos in monojet signatures at the Tevatron and at the LHC.Comment: 35 pages, 12 figures (including 3 in color); replacement is published version, including extra references, clarifications and some rescaling of some figure

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How Do Children Make Sense of their Parent's Mental Health Difficulties:A Meta-Synthesis

Children of parents who experience mental health difficulties (COPE-MHD) consistently demonstrate numerous negative outcomes, including risks of intergenerational continuity of mental health difficulties (MHD). Numerous studies have analysed the experiences and understanding of parents’ MHD from the perspective of COPE-MHD. This metasynthesis aims to capture, across available literature, the way in which COPE-MHD make sense of their parent’s MHD and how this perception impacts their life. For inclusion in the review, research articles were required to be published in peer-reviewed journals, apply qualitative methods of data collection and analysis and report on the direct accounts of COPE-MHD regarding their understanding or experience of their parents’ MHD. Five electronic databases were used; Academic Search Complete, CINAHL, MEDLINE, PsycINFO and Child Development and Adolescent Studies. Fourteen studies were included. Analysis produced three overarching themes. The findings illustrate children’s sophisticated biopsychosocial conceptualisation of the cause and process of their parent’s MHD. It also highlights how they utilise this understanding to manage the day-to-day concerns associated with their parent’s experience of MHD. Clinical implications highlight a need for services working with children, parents and families to more frequently enquire about parents’ MHD and to consider the outcomes of such enquiry in the psychological formulation of children and young peoples’ mental health and development. Limitations and recommendations for future research are presented