Related papers: Flavor changing neutral current constraints on sta…
Supersymmetry solves the gauge hierarchy problem of the Standard Model if the masses of supersymmetric partners of the SM particles are close to the weak scale. In this thesis, we argue that the supersymmetric Standard Model, while avoiding…
We consider six-dimensional supergravity with gauge group $SO(10)\times U(1)_A$, compactified on the orbifold $T^2 / \mathbb{Z}_2$. Three quark-lepton generations arise as zero modes of a bulk $\bf16$-plet due to magnetic flux of the…
We study gaugino-mediated supersymmetry breaking in a six-dimensional SO(10) orbifold GUT model where quarks and leptons are mixtures of brane and bulk fields. The couplings of bulk matter fields to the supersymmetry breaking brane field…
The Two Higgs Doublet model and its phenomenological implications are discussed. A brief survey on the present status of this model is given. In particular, we concentrate on the Two Higgs Doublet Model with Flavor Changing Neutral…
We consider supersymmetric extensions of the standard model with general non-universal soft breaking terms. We analyse in a model-independent way the constraints on these terms at the electroweak energy scale coming from gluino mediated…
A supersymmetric Pati-Salam model with wrapping number equal to 5 has been constructed in Type IIA orientifolds on $\mathbf{T}^6/(\mathbb{Z}_2\times \mathbb{Z}_2)$ with intersecting D6-branes recently. In particular, the string-scale gauge…
In supersymmetric grand-unified models, the lepton mixing matrix can possibly affect flavor-changing transitions in the quark sector. We present a detailed analysis of a model proposed by Chang, Masiero and Murayama, in which the…
We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10) grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We introduce…
We construct an extension of the Standard Model (SM) which is based on grand unification with Pati-Salam symmetry. The setup is supplemented with the idea of spontaneous flavour symmetry breaking which is mediated through flavon fields with…
Constraints from flavour changing neutral currents are discussed in the context of predictive Grand Unified Supersymmetric Theories. Uncertainties in the estimation of their amplitudes are minimized by using a successful mass matrix ansatz…
We provide a study of the phenomenology of orbifold compactifications of the heterotic string within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop…
We examine the infra-red structure of soft supersymmetry breaking masses of the squarks and sleptons in supersymmetric (SUSY) strong unification schemes where $\alpha_{GUT}\sim 0.2-1$. We show that combinations of soft masses approach fixed…
Flavor symmetry has been widely studied for figuring out the masses and mixing angles of standard-model fermions. In this paper we present a framework for handling flavor symmetry breaking where the symmetry breaking is triggered by…
In the context of the field theory limit of superstrings, we consider an almost realistic model of supersymmetry breaking by gaugino condensation which includes, through nonperturbative corrections to the K\"ahler potential, dilaton…
We discuss a scenario in which the supergravity induced soft terms, conventionally used for breaking supersymmetry, also lead to non-zero Majorana neutrino masses. The soft terms lead to the spontaneous violation of the lepton number at the…
We define a new class of Z' models with neutral flavour-changing interactions at tree level in the down-quark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavoured U(1)' gauge…
We present a new geometric approach to the flavour decomposition of an arbitrary soft supersymmetry-breaking sector in the MSSM. Our approach is based on the geometry that results from the quark and lepton Yukawa couplings, and enables us…
Soft supersymmetry breaking terms involving heavy singlet sneutrinos can be the dominant source of leptogenesis. The relevant range of parameters is different from standard leptogenesis: a lighter Majorana mass, M < 10^9 GeV (allowing a…
We explore the possibility that lepton family numbers and baryon number are such good symmetries of Nature because they are the global remnant of a spontaneously broken gauge symmetry. An almost arbitrary linear combination of these…
We derive predictions for Yukawa coupling ratios within GUTs generated from operators with mass dimension four and five. These relations are a characteristic property of unified flavour models and can reduce the large number of free…