The Mainz neutrino mass experiment

The Mainz neutrino mass experiment is investigating the endpoint region of the tritium β decay spectrum to determine the mass of the electron antineutrino. With its recently improved setup data were taken over more than 7 month in 1998 and 1999. For these measurements two different analyses are presented leading to m2ν = +0.6 ± 2.8 ± 2.1 eV2/c4 and m2ν = -1.6 ± 2.5 ± 2.1 eV2/c4, from which upper limits of mν < 2.8 eV/c2 (95 % C.L.) and mν < 2.2 eV/c2 (95 % C.L.) are derived. Only in one of six data sets was a clear indication for the anomaly, reported by the Troitsk group, found, and its postulated half year period is contradicted by our data. To push the sensitivity on the neutrino mass below 1 eV/c2 a new larger MAC-E spectrometer is proposed. Besides its integrating mode it could operate in a new non-integrating MAC-E-TOF mode