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This thesis considers the low-energy effective field theory of a new technicolor extension. The extension preserves the Standard Model Higgs boson and introduces a chirally symmetric technifermion sector, in the framework of the gauged linear sigma model. In the nearly conformal limit, the considered extension leads to a common origin of the Higgs- and Technisigma vacuum expectation values, relate
New stable particles with fairly low masses could exist if the coupling to the Standard Model is weak, and with suitable parameters they might be possible to produce at the LHC. Here we study a selection of models with the new particles being charged under a new gauge group, either U(1) or SU(N). In the Abelian case there will be radiation of gammavs, which decay back into the SM. In the non-Abeli
In this thesis, a holographic model for quantum chromodynamics (QCD) is used to estimate the electromagnetic contribution to the kaon mass difference. The principal ideas of the model are inspired by the AdS/CFT correspondence, which is believed to be exact. The calculation is first performed theoretically, highlighting the expansion of the result into a diagrammatic structure referred to as Witte
This thesis will investigate the possibility to have SU(2) gauge fields as the source to the Cosmic Inflation and/or to the Dark Energy. It will be explained that, under certain conditions, the Universe can be filled with vector fields without violating its isotropy. Those conditions are naturally fulfilled within the SU(2) gauge theory. Both Einstein's equations and the equations of motion
Chiral perturbation theory is an efficient effective theory to describe meson-meson scattering at low energy. An effective theory naturally introduces low energy constants and they are used, for example, to solve the ultraviolet divergences. The aim of this master thesis is to focus on meson-meson scattering to find some theoretical bounds on the coupling constants, based mainly on arguments from
One approach to understanding the observed hierarchy in quark masses is by using the Froggatt-Nielssen mechanism. In this model new exotic (and presumable yet undetected) particles are introduced. By forcing the particles of the Standard Model to interact with the postulated particles it is possible to create a mass suppression mechanism which can explain the observed quark mass relations. The me
The thesis treats the construction of a supersymmetric model, inspired by an E8 unfication scenario. Via the introduction of adjoint representation chiral superfields, in combination with the inclusion of a global generation symmetry, the Standard Model fermion candidates are protected from gaining any mass until electroweak symmetry breaking. In addition, an accidental global baryon symmetry proh
In this thesis a chirally symmetric technicolor model is investigated as an extension to the Standard Model. The extension is based on low-energy QCD, with a linear sigma model used to induce the additional degrees of freedom corresponding to the lightest particles of the new techni-sector. The main goal is to incorporate the Standard Model Higgs into the new model, as to explain its vacuum expect
High energy particle collisions involve complex physics, beyond analytical control. Instead, Monte Carlo event generators like Pythia have been used to simulate particle collisions since decades. A study of the production of heavy quarks (namely, charm and bottom) is presented for two different scenarios: lepton (e+e−) and hadron (pp) collisions. Electron- positron collisions at the Z0 resonance a
In this thesis a method for decomposing QCD colour structures into multiplet bases is described. The method is applicable for any number of gluons and quarks. To achieve the decomposition requires the knowledge of group theoretical weights, so-called Wigner 3j and 6j coefficients. The number of required coefficients have been calculated for up to 12 external gluons, and been shown to scale well in
We take a look at the properties of scalar fields in anti--de--Sitter space in five dimensions. More specifically we define bulk--to--boundary and bulk--to--bulk propagators for a five--dimensional scalar field and use these to calculate four--point functions. Finally we take a look at two--point functions and three--point functions and numerically calculate masses, residues and decay constants fo
The black hole information paradox is of central importance in the study of quantum gravity. The paradox states that quantum fields surrounding a black hole behave in ways that run into conflict with the unitarity of quantum mechanical time evolution. In the course of the past two years, new theoretical discoveries have made progress towards the paradox’s resolution, suggesting that unitarity can
Some of the shortcomings of the Standard Model of particle physics are the 'unnatural' value of the mass of the Higgs boson and the fact that the model cannot account for the process of baryogenesis - a mechanism which generates the observed asymmetry between matter and anti-matter in the Universe. The former is related to the fundamental scalar nature of the Higgs boson, connected to quad
In this thesis, we consider a 2-Higgs-doublet model with a gauged Froggatt-Nielsen mechanism as an extension of the standard model. We assume that (i) the theory at the electroweak scale is the low energy limit of a theory defined at a scale $\Lambda_{FN}$ (ii) the Yukawa couplings at $\Lambda_{FN}$ are generated by the Froggatt-Nielsen mechanism. The first assumption is enforced by requiring that
The Einstein-Hilbert Lagrangian for gravity is non-renormalizable at loop level. However, it can be treated in the effective field theory framework which means that gravity as an effective theory can be renormalized when a proper expansion of the effective Lagrangian is made. At the same time, the Feynman rules for gravity are very complicated, although the resulting amplitudes do not have the sam
We investigated the performance of basic jet subtraction, by the utilization of jet reconstruction generally used at the Large Hadron Collider (LHC). This was done by studying Z-bosons, in the dielectron decay channel, and the associated jet correlation in pp, pPb and PbPb collisions, using datasets generated by the Monte Carlo generator PYTHIA8. The PbPb collisions at $\sqrt{s_{NN}} = 2.76$ TeV a
Throughout this work we investigate a trinification-based grand unification theory (GUT) with a global family symmetry, as a radiative origin of the Standard Model (SM). We show that after spontaneous symmetry breaking of the trinification gauge group, we can in theory construct an effective left-right symmetric model (LRSM) which breaks to the SM gauge group through radiative breaking induced by
In recent years, the BaBar, Belle and LHCb experiments have observed an excess of $B\to D^{(*)}\tau\nu$ decays compared to Standard Model predictions. In this thesis, we investigate if it is possible to explain this excess with a two Higgs doublet model using the Froggatt-Nielsen framework. Two Higgs doublet models allow new decays at tree-level and the Froggatt-Nielsen mechanism gives an explanat
