Some Phenomenological Aspects In Neutrino Oscillations

Neutrino oscillation is one of the most important achievements in particle physics in last ten years. Compelling evidences of neutrino flavor transformations are obtained in many experiments, such as solar neutrino experiments(SNO), atmospheric neutrino experiments(SK), reactor neutrino experiments(KamLAND) and accelerator neutrino experiments(K2K,MINOS), which indicate that neutrinos have non-zero masses and non-trivial mixing. Now the standard picture of neutrino masses and mixing is three neutrinos with sub-eV masses and bi-large mixing.The main parts of this dissertation include three topics on different aspects of neu-trino oscillation and neutrino masses. The first one is devoted to the discussion of tribimaxmal pattern of neutrino mixing. We investigate three different methods of the deviation of the tribimaxmal mixing matrix, including charged lepton section correc-tions, radiative corrections and right-handed sector corrections. Before this, in chap-ter 2, we also discussed the main fundamentals of the standard model(SM) in particle physics and the Seesaw mechanism of neutrino mass generation.The second topic is about neutrino oscillation theory in quantum field theory(QFT). In chapter 3, after we reviewed the standard treatment of neutrino vacuum oscillation, we introduce two different models of neutrino oscillation in QFT, one is used to de-fine process-dependent flavor states and another proposed by Blasone and Vitiello(BV) is focused on the construction of flavor Fock states from mixing. Using these flavor states in the latter model, We check the consistency of the two models by calculating the amplitudes of interaction vertex in SM. We find that, at tree level, flavor changing charge(CC) current interactions emerge even if we carry out everything correctly. This means that we cannot define a neutrino flavor by the flavor of associated charged lepton and results in contradictions.We discuss the matter effects and statistical analysis of solar neutrinos as our third topic. In chapter 4, we discuss the resonance enhancement mechanism(MSW effect) which happens when neutrino propagates inside the Sun. After derived this effect in two-neutrino mixing approximation and in-three neutrino mixing, we discuss in de-tail the MSW effect with the generic mixing of three active neutrinos and Ns sterile neutrinos. We employ both analytical and numerical analysis to check the accuracy of our results. We also take into account the earth re-generation effects of solar neu- trinos at the end of this chapter. In chapter 5, we present our data analysis results of solar neutrino and reactor(KamLAND) neutrino experiments by using the least squares methods. In two-neutrino approximation, we give the global fit of the two oscillation parameters(△m2 and tan2θ), which exhibits the main feature of the LMA-MSW solu-tion of solar neutrino problem. In three-neutrino mixing hypothesis, we focus on the possible hint of non-zeroθ13. Our results give a significance of 1.2σ.Conclusions and future prospects are summarized in chapter 6.