Direct neutrino mass measurements

Direct neutrino mass experiments are complementary to searches for neutrinoless double β-decay and to analyses of cosmological data. The previous tritium beta decay experiments at Mainz and at Troitsk have achieved upper limits on the neutrino mass of about 2 eV/c2 . The KATRIN experiment under construction will improve the neutrino mass sensitivity down to 200 meV/c2 by increasing strongly the statistics and—at the same time—reducing the systematic uncertainties. Huge improvements have been made to operate the system extremely stably and at very low background rate. The latter comprises new methods to reject secondary electrons from the walls as well as to avoid and to eject electrons stored in traps. As an alternative to tritium β-decay experiments cryo-bolometers investigating the endpoint region of 187Re β-decay or the electron capture of 163Ho are being developed. This article briefly reviews the current status of the direct neutrino mass measurements.