Narrow Results

In this paper we obtain the exact mass-eigenstates of the Majorana physical neutrinos. We start by taking into account a general 3 × 3 mass matrix (ignoring any CP-phase violation). It is then diagonalized by exactly solving an appropriate set of equations. The solution provides straightforwardly the mass eigenvalues depending on the diagonal entries and mixing angles. Finally, the consequences of these analytical expressions are discussed assuming certain restrictions such as the global lepton number L = L_e - L_μ - L_τ (rigorously conserved or softly broken) and the μ - τ interchange symmetry. The minimal absolute mass in the neutrino sector is also obtained since the two plausible scenarios invoked above are employed.

Loop corrections induce a dependence on the momentum squared of the coefficients of the Standard Model Lagrangian, making highly nontrivial (or even impossible) the diagonalization of its quadratic part. Fortunately, the introduction of appropriate counterterms solves this puzzle.

An attempt is made to generate the bimaximal mixings of the three species of neutrinos from the textures of the right-handed Majorana neutrino mass matrices. We extend our earlier work in this paper for the generation of the nearly degenerate as well as the inverted hierarchical models of the left-handed Majorana neutrino mass matrices using the non-diagonal textures of the right-handed Majorana neutrino mass matrices and the diagonal form of Dirac neutrino mass matrices, within the framework of the see-saw mechanism in a model independent way. Such Majorana neutrino mass models are important in explaining the recently reported result on the neutrinoless double beta decay (0νββ) experiment, together with the earlier established data on LMA MSW solar and atmospheric neutrino oscillations.

The neutrino mixing matrix has been measured to be of a form consistent with tribimaximal mixing, while the quark mixing matrix is almost diagonal. A scheme based on flavour A₄ symmetry for understanding these patterns simultaneously is presented.

Various experiments use secondary neutrino beams produced by accelerators to study neutrino oscillations. In this article, we will review oscillation results from a number of those experiments (MINOS, OPERA), and focus more on results from T2K. This long baseline off-axis experiment uses a beam of muon neutrinos produced in J-PARC in Japan to study muon neutrino disappearance in order to measure atmospheric parameters, as well as studying electron neutrino appearance to measure the 13 mixing angle. We will present in particular very recent results of those measurements obtained by MINOS and T2K.