The three modified neutrino mass matrices in the SU(5) × U(2) model are studied focusing on the neutrino oscillation experiments. The model could be reconcile with the data of LSND. In the case of 〈φ1〉 6 = 0, the heaviest neutrino could be the hot dark matter; m3 ≥ 1eV, which means that CHORUS/NOMAD will find neutrino oscillations. In the special case of a = 1, which is a coefficient of 22 entr...

We discuss a six dimensional mass generation for the neutrinos. Active neutrinos live on a three-brane and interact via a brane localized mass term with a bulk sixdimensional standard model singlet (sterile) Weyl fermion, the two dimensions being transverse to the three-brane. We derive the physical neutrino mass spectrum and show that the active neutrino mass and Kaluza–Klein masses have a log...

In this brief note, we suggest that the accumulating neutrino data [1–3], including the recent results from KamLAND [4] and K2K [5], point to a relatively simple neutrino mass matrix. The data can be explained by oscillations between three active neutrinos with the atmospheric neutrino and K2K data explained by oscillation between the muon and the tauon neutrinos, and the solar neutrino and Kam...

Our present knowledge of neutrinos can be summarized in terms of the “standard neutrino scenario”. Phenomenology of this scenario as well as attempts to uncover physics behind neutrino mass and mixing are described. Goals of future studies include complete reconstruction of the neutrino mass and flavor spectrum, further test of the standard scenario and search for new physics beyond it. Develop...

We discuss neutrino mass and mixing in the framework of the classic seesaw mechanism, involving right-handed neutrinos with large Majorana masses, which provides an appealing way to understand the smallness of neutrino masses. However, with many input parameters, the seesaw mechanism is in general not predictive. We focus on natural implementations of the seesaw mechanism, in which large cancel...

We consider the simplest model which solves the solar and atmospheric neutrino puzzles, in the sense that it contains the smallest amount of beyond the Standard Model ingredients. The solar neutrino data is accounted for by Planck-mass effects while the atmospheric neutrino anomaly is due to the existence of a single righthanded neutrino at an intermediate mass scale between 109 GeV and 1014 Ge...

One of the most important tasks in neutrino physics is to determine the neutrino mass scale to distinguish between hierarchical and degenerate neutrino mass models and to clarify the role of neutrinos as dark matter particles in the universe. The current tritium β decay experiments at Mainz and Troitsk are reaching their sensitivity limit. The different options for a next generation direct neut...

If the tau neutrino is as heavy as 10 MeV which may have certain astrophysical implications, the neutrino mass pattern is studied so as to accommodate the new oscillation observations. It predicts that the electron neutrino has Marjorana mass around 0.05 eV. A supersymmetric model is described to realize the above scenario.

Neutrino oscillation experiments reveal that neutrinos have very small but finite masses. Since neutrinos have no masses in the standard model, we need to extend the standard model to induce the neutrino masses which coincide with the results of the neutrino oscillation experiments. It is possible that neutrino can have both of Dirac mass and Majorana mass. Majorana mass has the feature that it...

If a primordial magnetic field was present during photon decoupling and afterward, a finite neutrino mass could affect the Cosmic Microwave Background (CMB). In previous work [1], we studied the effect of a neutrino mass on the vector and tensor modes of the CMB power spectra. In this work, we also calculated the scalar mode and found that a neutrino mass also has a large effect on it. We decom...