Precise predictions for Higgs physics in a singlet extension of the standard model

Media type: E-Book; Thesis

Title: Precise predictions for Higgs physics in a singlet extension of the standard model

Contributor: Boggia, Michele [Author]

Published: Freiburg, April 2018

Extent: 1 Online-Ressource (223 Seiten); Diagramme

Language: English

DOI: 10.6094/UNIFR/15866

Identifier:

Keywords: Higgs-Teilchen > Quantenchromodynamik > Renormierung > Monte-Carlo-Simulation > Higgs-Mechanismus > Standardmodell > Elementarteilchenphysik > Dunkle Materie
Standardmodell > Higgs-Mechanismus > Higgs-Teilchen

Origination:

University thesis: Dissertation, Albert-Ludwigs-Universität Freiburg, 2018

Footnote:

Description: Abstract: The experiments at the LHC are studying the fundamental interactions of the elementary constituents of matter, in particular in order to understand how the electroweak symmetry breaking mechanism is realized in nature. The hope is to find traces of new physics by observing deviations from the Standard Model (SM) expectations. For the interpretation of the experimental data, precise theoretical predictions are needed, both within the SM and its extensions. In this thesis, we consider a Singlet Extension of the SM with a Z2 -symmetric singlet sector in the Lagrangian and non-vanishing vacuum expectation values (vevs) both for the scalar doublet and singlet fields. The model predicts the presence of two Higgs bosons, and the non-vanishing vev for the scalar singlet leads to mixing between the two bosons. We parametrize the scalar sector of the model by a mixing angle α, a scalar self-coupling λ12 and the masses of the two Higgs bosons of the model. Considering the lightest of the two scalars of the theory to be the Higgs boson with mass about 125 GeV discovered at the LHC, we discuss theoretical constraints from perturbativity of the couplings and vacuum stability in order to find valid input values for the unknown parameters of the theory. We renormalize the theory adopting two schemes, which includes MS renormalization conditions for the parameters of the theory that are not directly accessible by experiments and on-shell renormalization conditions for all the other parameters. We investigate the conversion of the input parameters between the two schemes, finding potentially large effects. For some scenarios proposed in the literature, we compute next-to-leading-order electroweak and QCD corrections to the decays h → WW/ZZ → 4 fermions of the light Higgs boson and compare the results obtained in the two renormalization schemes. We solve the renormalization-group equations for the parameters α and λ12 , which are defined by MS renormalization conditions, and study the dependence of the h→4f decay widths on the renormalization scale. The inclusion of next-to-leading-order corrections reduces the (unphysical) scale dependence of the results drastically. For each scenario, the total decay width for the process h→4f is computed as a function of the mixing angle and compared to the SM result, finding relative deviations below 10%. Differential distributions do not show significant distortions by effects beyond the SM. The calculation are imp ...

Access State: Open Access

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