Direct neutrino mass measurements

Direct neutrino mass measurements are based on high precision spectroscopy studies close to the kinematic end-point of low-energy β-emitters such as 3H and 187Re. Relying only on energy-momentum conservation in β-decay, they offer the only model-independent method to measure the absolute ν-mass scale with sub-eV sensitivity. The two most sensitive detection principles, electrostatic retarding spectrometers and microbolometers, are complementary to each other, and two experiments are currently being prepared to explore ν-masses down to m(ν) = 200 meV. β-spectroscopy will thus allow to constrain the role of neutrino hot dark matter in structure formation, as well as to explore the parameter region of ν-mass scenarios with quasi-degenerate pattern. The MARE project will investigate the β-decay of 187Re with bolometers based on metallic Re and AgReO4 in a two-staged approach: in a phase-I set-up a sensitivity of m(ν) = 2 eV is expected, forming the basis for a later sub-eV phase-II. The Karlsruhe Tritium Neutrino (KATRIN) experiment is currently being set-up on the site of Tritium Laboratory at KIT. The experiment will combine an ultra-luminous windowless gaseous tritium source with a high resolution electrostatic spectrometer and offer an unprecedented precision in β-decay studies, pushing this technique to its technological limits. First KATRIN measurements with 3H after successful system integration are expected for mid-2011. This contribution gives a status report and outlook for both experiments and discusses the impact of direct ν-mass experiments on astroparticle physics.