Family symmetries and radiative corrections in multi-scalar extensions of the Standard Model

Jonas Wessén

Research output: ThesisDoctoral Thesis (compilation)

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The four articles contained in this thesis all concern aspects of model building beyond the Standard Model (BSM). While Paper I mainly serves as a ``tool paper'' in which the results can be used to simplify certain calculations of one-loop effects from new heavy particles, Paper II--IV all deal with consequences of family symmetries in several BSM scenarios.

Paper I. We derive expressions for any number of derivatives of the Coleman-Weinberg potential in a general renormalisable four-dimensional field theory with arbitrary number of fields with spin~$\leq$~1. These correspond to the one-loop contributions to scalar $n$-point functions neglecting external momenta. The results are applied to two singlet extensions of the Standard Model, where we study the one-loop effects on the triple-Higgs coupling from the new exotic heavy states.

Paper II. In this paper we study a non-supersymmetric trinification theory where a novel $\mathrm{SU}(3)_F$ family symmetry is imposed on the model. The tree-level scalar potential often has a global minimum where the trinification gauge group is broken to a Left-Right symmetric gauge group, and after integrating out all particles with masses of the order of the grand unification scale we show that the renormalisation group is able to trigger a radiative breaking down to the Standard Model gauge group with light Higgs doublets still remaining in the spectrum.

Paper III. This paper is about a supersymmetrised version of the $\mathrm{SU}(3)_F$ symmetric trinification model of Paper II. The absence of an appropriate scalar potential minimum is rectified by adding novel gauge adjoint chiral superfields. The resulting superpotential allows for a breaking of the grand unification symmetry, while all subsequent symmetry breaking scales are given by soft supersymmetry breaking parameters. The tree-level mass spectrum resulting from this soft breaking of supersymmetry is discussed.

Paper IV. A three Higgs doublet model is introduced with a $\mathrm{U}(1) \times \mathrm{U}(1)$  family symmetry that simultaneously enforces a Cabibbo quark mixing under charged current interactions and forbids tree-level flavour changing neutral currents. Furthermore, a hierarchy in the vacuum expectation values of the three doublets produces a SM-like Higgs boson and hierarchical fermion masses, and also causes the exotic scalar states to couple most strongly to the second quark family. A search strategy for the lightest charged scalar boson in the model is proposed that utilises the $c \bar{s}$ fusion channel, and is shown to be capable of probing a large portion of the model's parameter space. This is formulated in a model independent manner such that it can be directly applied to any model with the same discovery channel.
Original languageEnglish
Awarding Institution
  • Lund University
  • Pasechnik, Roman, Supervisor
  • Rathsman, Johan, Assistant supervisor
Award date2018 May 18
Place of PublicationLund
ISBN (Print)978-91-7753-671-0
ISBN (electronic) 978-91-7753-672-7
Publication statusPublished - 2018

Bibliographical note

Defence details
Date: 2018-05-18
Time: 13:00
Place: Hall K404, Department of Physics, Sölvegatan 14A, Lund
External reviewer(s)
Name: Porod, Werner
Title: Prof. Dr.
Affiliation: Theoretische Physik II, Universität Würzburg, Germany

Subject classification (UKÄ)

  • Subatomic Physics


  • Beyond the Standard Model
  • Trinification
  • Grand Unification
  • Three Higgs doublet models
  • Coleman-Weinberg potential, Supersymmetry, Left-Right symmetry
  • Fysicumarkivet A:2018:Wessén


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