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

Jonas Wessén

Research output: ThesisDoctoral Thesis (compilation)

## Abstract

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 language English Doctor Lund University Pasechnik, Roman, SupervisorRathsman, Johan, Assistant supervisor 2018 May 18 Lund Lund University, Faculty of Science, Department of Astronomy and Theoretical Physics 978-91-7753-671-0 978-91-7753-672-7 Published - 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
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## Subject classification (UKÄ)

• Subatomic Physics

## Keywords

• 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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• ### Heavy charged scalars from cs¯ fusion: a generic search strategy applied to a 3HDM with U(1) × U(1) family symmetry

Camargo-Molina, J. E., Mandal, T., Pasechnik, R. & Wessén, J., 2018 Mar 1, 2018, 3, 24.

Research output: Contribution to journalArticlepeer-review

Open Access
7 Citations (SciVal)
• ### Reviving trinification models through an E6 -extended supersymmetric GUT

Camargo-Molina, J. E., Morais, A. P., Ordell, A., Pasechnik, R., Sampaio, M. O. P. & Wessén, J., 2017 Apr 1, 95, 7, 075031.

Research output: Contribution to journalArticlepeer-review

20 Citations (SciVal)
• ### All one-loop scalar vertices in the effective potential approach

Camargo-Molina, J. E., Morais, A. P., Pasechnik, R., Sampaio, M. O. P. & Wessén, J., 2016 Aug 1, 2016, 8, 73.

Research output: Contribution to journalArticlepeer-review

Open Access
18 Citations (SciVal)