Parametrization of the Energy Spectrum in the Tritium Beta Decay

Taking into account mixings among neutrino states, the end of the energy spectrum of the electron in the tritium beta decay is investigated. It is shown that for real energy resolutions of a spectrometer, $\Delta E > 0.08$ eV, the effective electron neutrino mass should [not] be taken in the form $m_\beta^{(1)} = \sqrt{\sum|U_{ei}|^2 m_i^2} [m_\beta^{(2)} = \sum|U_{ei}|^2 m_i$.