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Abstract

In this thesis, the type I and type II see-saw models are considered separately as the mechanism to generate small neutrino masses and the radiative corrections to the Higgs mass induced by these models are studied. Especially, the influence of imposing naturalness is tested. As the naturalness criterion, it is assumed that quantum corrections should not be larger than the Higgs mass. Imposing this condition, limits on the new mass scale introduced in each model can be set, so that no hierarchy problem arises. For the type I, it is found that the mass of the right-handed neutrino could take values up to O(107 GeV) without generating large corrections. For the type II, the parameter space of the extended scalar potential is first restricted by imposing vacuum stability, unitarity of scattering processes and experimental constraints, before testing the influence of imposing naturalness. Only small values of the triplet vacuum expectation value, O(eV), which give rise to sizeable Yukawa couplings, are considered. In this scenario, there exist a large parameter space satisfying the vacuum stability, unitarity and experimental constraints. Of this parameter space, all sets of parameters satisfy the naturalness condition for triplet masses below 1 TeV and a large subset satisfies naturalness for masses between 1 TeV and 3 TeV. If the triplet mass were located in this energy range, as preferred by naturalness, new particles corresponding to the triplet might be detectable at the Large Hadron Collider or future colliders and also lead to significant signals in lepton flavour violation experiments.