Beta decay in external field and neutrino mass

The results of the investigation of electromagnetic field effects on the process of beta decay are used for analyzing experimental data on direct neutrino mass search.Comment: 7 pages, 7 figures, late

On the Effective Mass of the Electron Neutrino in Beta Decay

In the presence of mixing between massive neutrino states, the distortion of the electron spectrum in beta decay is, in general, a function of several masses and mixing angles. For $3\nu$-schemes which describe the solar and atmospheric neutrino data, this distortion can be described by a single effective mass, under certain conditions. In the literature, two different definitions for the effective mass have been suggested. We show that for quasi-degenerate mass schemes (with an overall mass scale $m$ and splitting $\Delta m^2$) the two definitions coincide up to $(\Delta m^2)^2/m^4$ corrections. We consider the impact of different effective masses on the integral energy spectrum. We show that the spectrum with a single mass can be used also to fit the data in the case of $4\nu$-schemes motivated, in particular, by the LSND results. In this case the accuracy of the mass determination turns out to be better than $(10 - 15)$.Comment: 15 pages, Version to appear in Phys. Lett.

Non-Oscillation Searches of Neutrino Mass in the Age of Oscillations

We focus on the implications of the oscillations for the shape of nuclear beta-spectrum (=direct search for nu mass). This is of interest because of the existing bound, m_(nu_e)<2.2 eV, that could improve by one order of magnitude with future experiments. We stress important connections with the results of Liquid Scintillator Neutrino Detector, nu_e disappearance experiments, supernova neutrinos and neutrinoless double beta decay.Comment: 3 pages, 1 figure. Matches the version to appear in the Proceedings of NOW 2000 Worksho

Testing Lorentz invariance violations in the tritium beta-decay anomaly

We consider a Lorentz non-invariant dispersion relation for the neutrino, which would produce unexpected effects with neutrinos of few eV, exactly where the tritium beta-decay anomaly is found. We use this anomaly to put bounds on the violation of Lorentz invariance. We discuss other consequences of this non-invariant dispersion relation in neutrino experiments and high-energy cosmic-ray physics.Comment: 11 pages, 2 figures, elsart style. Some references added. Final version to appear in Physics Letters

Neutrino Mass^2 Inferred from the Cosmic Ray Spectrum and Tritium Beta Decay

An earlier prediction of a cosmic ray neutron line right at the energy of the knee of the cosmic ray spectrum was based on the speculation that the electron neutrino is a tachyon whose mass is reciprocally related to the energy of the knee, $E_k$. Given the large uncertainty in $E_k$, the values of ${m_\nu}^2$ corresponding to it are consistent with values recently reported in tritium beta decay experiments.Comment: Published as Phys. Lett. B 493 (2000) 1-

Probing Neutrino low energy and mass scales

Low energy neutrino processes are ideal probes for new Physics beyond the Standard Model. Cosmological observations and rare nuclear processes can test neutrino mass scales and give definite answers to unsolved basic questions like the Majorana/Dirac nature of the neutrino.Comment: 6 Pages, summary of the ``Probing low energy and mass scales'' session during the Neutrino Oscillation Workshop NOW2006, Otranto, Italy, September 9-16 200