Calorimetric approach to the direct measurement of the neutrino mass: The MARE project

Abstract

The direct kinematic measurement of the electron anti-neutrino mass is one of the tools available in order to assess the neutrino absolute mass scale. Due to the difficulty of this kind of measurements it is important to have more than one experiment involved in this search. In particular the calorimetric approach can be alternative and complementary to the "traditional" tritium end-point study performed with beta spectrometers. In this context the MARE experiment, which is based on the study of the beta spectrum of a 187Re source embedded in a low temperature microcalorimeter, will play a crucial role. The MARE project will be realized thanks mainly to the convergence of three experiences, matured within the MANU (Genova), MIBETA (Milano) and Wisconsin-NASA groups. In this talk, I will present the status of the MARE experiment and I will show the potential of the calorimetric approach, giving an estimate of the present and foreseen statistical sensitivity on neutrino mass and illustrating which the possible sources of systematic uncertainty are. I will mainly focus on the activities in progress to reach 2 eV sensitivity, using arrays of semiconductor thermistors and AgReO4 absorbers. The results so far obtained in this sector will be presented and discussed. The final aim of the MARE project is to reach a statistical sensitivity of about 0.2 eV, the same predicted for the next generation spectrometric experiment KATRIN. As I will discuss, this result can be achieved thanks to a further implementation of the detector technologies (under study), a multiplication of the read-out channels and a complete understanding of all sources of systematic uncertainty.