Double Beta Decay
Ezio Previtali (INFN, Italy)
The existence of neutrino oscillations demonstrates that neutrinos
have a finite mass and mixing. However some relevant characteristics
of neutrinos are not accessible to oscillation experiments. Only
experiments sensible to the linear combination of neutrino masses have
the capabilities to fix the neutrino mass scale and, for a non
vanishing neutrino masses, also its nature, Dirac or Majorana, became
important information. In this framework neutrinoless double beta
decay is worldwide considered the most powerful tool to establish
neutrino properties. This rare decay will be observed only if
neutrinos are massive Majorana particles and it can determine the
particle mass scale Many experiments was made in the past to observe
this decay but no clear evidence was found. Actually a very strong
effort is devoted to prepare the next generation double beta decay
experiments using more sensitive approaches. The present status of
experiments for neutrinoless double beta decay will be reviewed. Next
generation experiments designed to reach mass scale value of the order
of few tens of eV will be discussed.