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Typical working day..

Roman Pasechnik

Senior lecturer

Typical working day..

Phenomenology in multi-scalar extensions of the Standard Model


  • Astrid Ordell

Summary, in English

This thesis is composed of four papers, which all treat various extensions to the Standard Model (SM). The first two papers concern a particular supersymmetric, grand-unified theory (GUT), while in the latter two, we classify anomaly-free implementations of two-Higgs doublet models (2HDM) with a gauged abelian symmetry.

Paper I. In this paper, we present an alternative solution for avoiding GUT-scale lepton masses in so-called trinification based GUT-models (T-GUTs). Rather than introducing several copies of the tri-triplets, which is the conventional approach, we solve the issue by embedding the symmetries into an E8 group.

Paper II. This paper involves a more detailed study of the model proposed in Paper I. Some of its features is an absence of the mu-problem and a universal Yukawa coupling for all chiral fermions.

Paper III. Here, we classify all anomaly-free implementations of a 2HDM with a gauged Abelian symmetry and the SM fermion content. The resulting 11 models are then compared under a range of experimental bounds, from which we identify the most promising ones.

Paper IV. In this paper, we again classify and compare all anomaly-free implementations of a 2HDM with a gauged Abelian symmetry, but this time around also including two generations of right-handed neutrinos. The right-handed neutrinos are incorporated to provide a mechanism for the neutrinos to obtain a mass, here via a type-I seesaw mechanism. In total, there are 16 valid models, which are all compared, both for normal- and inverted ordering. Two models are identified as the most promising candidates for future studies.


  • Theoretical Particle Physics

Publishing year




Document type



Lund University


  • Subatomic Physics


  • BSM, 2HDMs
  • BSM, 2HDMs




  • Roman Pasechnik


  • ISBN: 978-91-7895-570-1
  • ISBN: 978-91-7895-571-8

Defence date

18 September 2020

Defence time


Defence place

Lundmarksalen, Sölvegatan 27, Lund. Join via zoom: Lösenord: 497457


  • David Miller (Dr.)