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Abstract

Abstract In this thesis, we systematically study neutrino mass models that only generate
the dimension-5 Weinberg operator at loop-level. After an introduction to representation
theory, fermion masses and see-saw mechanisms, we search for radiative neutrino
mass models with a minimal number of new multiplets which do not require a new symmetry
beyond the Standard Model gauge group. New coloured fields are also allowed. It
can be shown that there is no radiative neutrino mass model with only two new fermionic
multiplets. In addition, there exists a unique model with three new fermionic multiplets.
A subsequent discussion of potential dark matter candidates present in some of the models
reveals that all of them decay too quickly to account for dark matter. In the three-fermion
model, they even decay too quickly to lead to displaced vertex signatures at the Large
Hadron Collider (LHC). In addition, a connection between coloured neutrino mass models
and B-physics anomalies is discussed. Furthermore, we consider radiative neutrino
mass models from a SU(5) grand unified theory perspective and study their compatibility
with unification and proton decay bounds. We were able to find out that for a group of
models with new vector-like fermion unification in agreement with proton decay bounds
is possible.