Sökresultat

We present our studies of four-jet double parton scattering production in proton-nucleus collisions within the framework of the pythia8 event generator. We demonstrate that double absorptive processes in pA generated by the Angantyr model in pythia8 give an enhancement of the total double parton scattering cross section similar to the predictions by Strikman and Treleani in 2001. Additionally, we

In this paper the Poisson bracket algebra for the open massless relativistic string in the one-space-and one-time-dimensional case is considered. In order to characterize the orbit of the system the directrix function, i.e., the orbit of one of the endpoints of the string, is used. It turns out that the Poisson bracket algebra is of a very simple form in terms of the parameters of the directrix fu

Top quark pairs production and decay are considered in the framework of the smeared-mass unstable particles model. The results are in good agreement with the previous ones in the literature. Suggested approach significantly simplifies calculations compared to the standard perturbative one.

We calculate cross-section of the near-threshold three-boson production at the ILC with an account of their instability and a principal part of NLO corrections. The calculations are fulfilled within the framework of the model of unstable particles with smeared mass. We show that the contribution of finite width (instability) is large in the resonance Higgs-mass range and should be taken into accou

In this work, we consider expressions for the masses and decay constants of the pseudoscalar mesons in SU(3) chiral perturbation theory. These involve sunset diagrams and their derivatives evaluated at p2=mP2 (P=π, K, η). Recalling that there are three mass scales in this theory, mπ, mK and mη, there are instances when the finite part of the sunset diagrams do not admit an expression in terms of e

I present higher loop order results for several calculations in Chiral perturbation Theory. 1) Two-loop results at finite volume for hadronic vacuum polarization. 2) A three-loop calculation of the pion mass and decay constant in two-flavour ChPT. For the pion mass all needed auxiliary parameters can be determined from lattice calculations of ππ-scattering. 3) Chiral corrections to neutron-anti-ne

The recent experimental measurement of the muon g−2 at Fermilab National Laboratory, at a 4.2σ tension with the Standard Model prediction, highlights the need for further improvements on the theoretical uncertainties associated to the hadronic sector. In the framework of the operator product expansion in the presence of a background feld, the short-distance behaviour of the hadronic light-by-light

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

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

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

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

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 Schwarzschild metric and the Kerr metric describe the gravitational fields around static and rotating black holes, respectively. Here, we derive the Kerr metric in a simpler way than how it was derived originally and determine the stability of the Schwarzschild metric. The Kerr metric was derived by using the Einstein-Hilbert action as well as directly from the Einstein field equations. In ord

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

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

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

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