UC Riverside

In this thesis I will summarize the research and the work I have contributed with, during the years of my PhD pursue. The focus of research includes the mysterious origin of Neutrino masses, the nature of Dark Matter, relation between existence of Dark Matter and the character of Neutrino mass mechanism, origin of the Pontecorvo$–$Maki$–$Nakagawa$–$Sakata (PMNS) matrix, CP violation in the leptonic sector and their relation to physics at high energy scale. Models simultaneously explaining several of the above have been developed. Study of these models' phenomenology and possible discovery channels at Large Hadron Collider (LHC) and International Linear Collider (ILC) in the future have been performed as well. Study of new models unifying all fundamental forces have been also pursued, leading to the prediction of new exotic particles interacting through new forces of nature.