MECHANISMS OF MASS GENERATION FOR NEUTRINOS IN NON- SUPERSYMMETRIC GUTS BASED ON SU(5)

The strong, weak and electromagnetic forces, which are the three fundamental forces in nature other than gravity, form the Standard Model (SM) gauge theory. Since it is not possible to combine the electromagnetic and weak interaction constants under SM with the strong interaction constant at high energies, Grand Unification Theories have begun to be developed. The Georgi-Glashow model is the first major unification theory that put forward by adding the strong interaction to the electromagnetic and weak interactions that are possible to combine in the SM, aiming to transform it into a single interaction constant. The three fundamental forces mentioned in Georgi-Glashow (GG) SU(5) gauge theory continue to not coalesce at high energies (1015-16 GeV). The mass of neutrinos, which are known to have mass today, cannot be explained in a natural way in the SM gauge theory, and neutrinos continue to be massless in the GG model. Another shortcoming of the GG model is that the mass ratios of charged leptons and quarks are not compatible with the experiments. In this thesis, a non-supersymmetric and renormalizable model will be constructed by adding scalars and fermions in the 45 and two 75 representations in SU(5), respectively, to the GG model. While correcting the mass ratios of charged lepton and quark with 45 scalar fields, at least two neutrino masses will be calculated with two 75 fermion fields, and it will be revealed whether the neutrino mass relations have normal or inverted hierarchy. Neutrino masses will be explained by the Type-1 seesaw mechanism. Since the 75 fermion fields are a real representation, our model does not contain anomalies. The split multiplet in the 45 scalar representation with the same quantum numbers as the Higgs in SM makes our model a two-Higgs-doublet model. Interaction constants that do not unify in the SM and GG model will be provided to do by the inclusion of scalars and fermions in the 45 and 75 representations in the flow at different intermediate scales using mass relations. Constraints from proton decay experiment to GUT scale and from cosmological calculations to neutrino masses will be considered.