Newest results from the Mainz Neutrino Mass Experiment

The Mainz neutrino mass experiment investigates the endpoint region of the tritium β decay spectrum with a MAC-E spectrometer to determine the mass of the electron antineutrino. By the recent upgrade the former problem of dewetting T ₂ films has been solved and the signal-to-background-ratio was improved by a factor of 10. The latest measurement leads to m_v² = -3.7 ± 5.3 _stat ± 2.1 _sys eV ²/c ⁴, from which an upper limit of m_v < 2.8 eV/c ² (95 % C.L.) is derived. Some indication for the anomally, reported by the Troitsk group, was found, but its postulated half year period is contradicted by our data. To push the sensitivity on the neutrino mass below 1 eV/c ² a new larger MAC-E spectrometer is proposed. Besides its integrating mode it could run in a new non-integrating operation MAC-E-TOF mode.