Investigating the Majorana nature of neutrinos, Galactic Dark Matter and Solar Axions Searches using thermal detectors in low background observatories

Neutrinos were proposed by W. Pauli as a remedy to explain nuclear beta decay. Now they are essential in our understanding of the Universe. In this talk I will show how Neutrino-less Double Beta Decay has a key role in determining the Majorana versus Dirac nature of neutrinos and as confirmation of neutrino mass values different from zero, as proofed by neutrino oscillation experiments. Neutrino-less Double Beta Decay studies require, in particular, the use of high-energy resolution detectors such as thermal detectors in low background observatories. The large detector mass of some thermal detector, the low energy threshold of a few keV and low background environment make such a kind of experiment well suited for direct detection of galactic Dark Matter particles and solar Axions.