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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
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
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 Master thesis, two directions have been explored to improve the current parton shower algorithm of the event generator Pythia. Firstly, three choices of transverse-momentum-ordered evolution variable have been studied for final-state radiation in order to allow more flexibility within the algorithm. These three choices turn out to be valid but they lead to more technical implementations th
We study the key properties of the quantum SU(2) Yang-Mills ground state and its possible role in the early Universe, in particular, as a driver of Cosmic Inflation. Using the effective action approach and separating the Yang-Mills field potential into homogeneous (condensate) and inhomogeneous (fluctuations) components, we reproduce the conformal-time solutions for the two different types of the
An analysis of two-particle angular correlations was recently performed on measurements taken from pp collisions at $\sqrt{s}$ = 7 TeV by ALICE at the LHC. The correlations for mesons are in good agreement with simulations performed in Monte Carlo event generators such as PYTHIA and PHOJET, but there is a significant difference for baryons. We here investigate particle production mechanisms in PYT
We review the factorization theorem for the production of a heavy color-neutral final state with a transverse momentum much smaller than its invariant mass in the framework of soft collinear effective field theory (SCET). This phase space region is plagued by large logarithms of widely separated scales, including large logarithms of rapidity ratios, that need to be resummed for sensible results. I
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
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
The possibility to have a strongly first order electroweak phase transition, which is one of the Sakharov conditions for electroweak baryogenesis together with $\mathcal{CP}$ violation and baryon number violation, in general Two-Higgs-Doublet Models (2HDMs) is here investigated. Different kinds of $\mathbb{Z}_{2}$ breaking beyond standard assumptions are studied, in particular by allowing it to be
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 we investigate the properties of a specific two Higgs Doublet Model (2HDM) that can be used to explain the data on B->Dtu and B->D*tu, which deviate from the Standard Model (SM) by 3.4 sigma. The 2HDM is the simplest extension of the Standard model scalar sector. Phenomenologically it is very rich with 4 new Higgs bosons: 2 neutral and an electromagnetic charged pair. The 2HDMs exhi
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
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
