The Status of the MARE Experiment with 187 Re and 163 Ho Isotopes

Neutrino oscillation experiments have proved that neutrinos are massive particles but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. The laboratory experiments dedicated to effective electron-neutrino mass determination are the ones based on the study of single beta decay or electron capture (EC) decay. Exploiting only on energy-momentum conservation, this kinematic measurement is the only one which permits to estimate neutrino masses without theoretical assumptions on neutrino nature and it is truly model-independent. To date the most competitive isotopes for a calorimetric measurement of the neutrino mass are 187Re and 163Ho. While the first decays beta, the latter decays via electron capture, and both have a Q-value around 2.5 keV. The measurement of 163Ho EC is an appealing alternative to the 187Re beta decay measurement because few nuclei are needed and it is a self-calibrating measurement. In this context the MARE project, based on rhenium thermal detectors has been born.