Neutrinoless Double Beta Decay in Theories Beyond the Standard Model
  Neutrinoless double beta decay pops up almost in any extension of the standard model. It is perhaps the only process, which can unambiguously determine whether the massive neutrinos are Majorana or Dirac type particles. In addition from the lifetime of this decay, combined with sufficient knowledge of the relevant nuclear matrix elements, one can set a constraint involving the neutrino masses. Furthemore, if one incorporates the recent results of the neutrino oscillation experiments, one can determine or set a stringent limit on the neutrino mass scale. In addition one may obtain usefull information regarding the presence of right handed currents and the right handed neutrino mass scale. One can also constrain the parameters of supersymmetry and, in particular, set limits in of R-parity violating couplings as well as get information about extra dimensions. 
J.D. Vergados