Measurement of the Mass of the Electron Neutrino Using Electron Capture in 163Ho

The mass of the electron neutrino has been recently investigated using electron capturing isotopes including 163Ho [1,2,3], 193pt [4] and so on. There are two ways to measure mνe; one proposed by A. De Rujula [5] of CERN which is essentially based on three body phase space in radiative electron capture process, and another that utilizes the mνe-dependence of. the electron capture rate, which was discussed by Bennett et al. [6]. Considerations of the intensity of internal bremsstrahlung at electron capture in a 163Ho source, indicate that the first approach is very difficult [7,8]. Therefore, for the time being, we decided to pursue the second approach [9].