Tritium beta decay, neutrino mass matrices, and interactions beyond the standard model - art. no. 093013

The interference of charge changing interactions, weaker than the V-A stand ard model (SM) interaction and having a different Lorentz structure, with t hat SM interaction, can, in principle, produce effects near the end point o f the tritium beta decay spectrum which are of a different character from t hose produced by the purely kinematic effect of neutrino mass expected in t he simplest extension of the SM. We show that the existence of more than on e mass eigenstate can lead to interference effects at the end point that ar e stronger than those occurring over the entire spectrum. We discuss these effects both for the special case of Dirac neutrinos and the more general c ase of Majorana neutrinos and show that, for the present precision of the e xperiments, one formula should suffice to express the interference effects in all cases. Implications for "sterile" neutrinos are noted.