Some Studies On Two Typical Neutrino Flavor Symmetries

In the Standard Model,neutrinos are strictly massless.However,a large number of experiments on neutrino oscillations have shown that neutrinos are massive and lepton flavors are mixed,which indicates that the Standard Model is incomplete.The seesaw mechanism is widely accepted because it naturally explains the minuscule mass of neutrinos.At the same time,the seesaw mechanism also offers the leptogenesis mechanism which can explain the baryon asymmetry of the Universe.Before its value was experimentally determined,the extreme possibility of ?₁₃being van-ishingly small was popularly conjectured,then the tribimaximal(TBM)mixing pattern and the-interchange symmetry were proposed.However,the experimental observation of a rela-tively large ?₁₃of the Daya Bay motivates us to forsake or modify these corresponding flavor symmetries.The first trimaximal neutrino(TM1)mixing and ?-? reflection symmetry attract people's attention because they can explain the current neutrino oscillation data.In this thesis,we make some studies on the two typical neutrino flavor symmetries:TM1mixing and ?-? reflection symmetry.In the first work,in the general seesaw framework,we explore the special textures of M_Dthat can naturally yield TM1 mixing in the basis of M_R being diagonal and their phenomenological implications.TM1 mixing will be achieved if the three columns of_Dare proportional to(2,-1,1)^T,(x,1+x,1-x)^T and (y,1+y,1-y)^T,respectively.Our analysis is limited to the case that three elements in the same column in_Dhave the same phase.Then we gradually take some special values for all the free parameters,so that M_Dhas simpler textures.And we study the influence of these phenomenologically-viable special structures on neutrino parameters and leptogenesis.In the second work,we make an attempt to embed the ?-? reflection symmetry in the Friedberg-Lee neutrino model(which employs a translational flavor symmetry and keeps one neutrino mass vanishing)and study the consequences of such a combination.