Can electron capture tell us the mass of the neutrino?

Abstract

The neutrino masses are one of the most important open problems in particle physics. Presently major efforts are underway to measure the electron antineutrino-mass by the triton beta decay [] and the effective Majorana neutrino mass by the double beta decay []. The best way to determine the neutrino mass by electron capture was assumed to be in . The total decay energy of the excited daughter atom has for all excitations the same upper energy limit of the Q-value minus the mass of the electron neutrino. Recently Robertson [] claimed, that the excitation of the two-hole states makes the determination of the neutrino mass by this method practically impossible. But Faessler and Simkovic [] showed, that the influence of the two-hole states is less than 1% near the Q-value, the area relevant for the determination of the neutrino mass. Even weaker are the contributions of the three-hole states []. The upper end of the calorimetric deexcitation spectrum of Dy is dominated by the highest energy one-hole resonance. With a Lorentzian profile of this resonance one has to fit after including the experimental sensitivity four parameters: (1) the neutrino mass, (2) the Q-value, (3) the width of the resonance and (4) its strength. This contribution discusses the problems of the determination of the neutrino mass by electron capture in . The conclusion of this work is, that the determination of the electron neutrino mass by electron capture in is difficult, but (probably) not impossible.