Phenomenology of neutrinos and possible SO(10) origins of fermion masses and mixings

Important but yet unanswered questions in neutrino physics are the neutrino mass hierarchy, precision determination of mixings and CP violation. A widely studied mixing scheme upon which many models are based is tri-bimaximal mixing. We emphasize the importance of alternative mixing schemes and confront their predictions with current data on neutrino mixings. Where necessary we show how perturbations of the leading order predictions can result in viable schemes. Further we study the prospects to test the inverted hierarchy with neutrinoless double beta decay. We find that the lower limit of the effective neutrino mass relevant for this process and hence the prospects to experimentally exclude the inverted hierarchy are highly sensitive to the neutrino mixing angle θ12. We further take into account uncertainties from nuclear physics. Next we analyze the possibility to explain the origin of fermion masses and mixings as well as the baryon asymmetry within renormalizable Grand Unified Theories based on SO(10), including effects of renormalization group evolution. Models with different Higgs representations are considered. After constraining the model parameters with experimental data we give the model predictions for undetermined observables; for the leptonic CP violating phase we also show the ranges allowed at 68% C.L.