Observable Majoron Emission in Neutrinoless Double Beta Decay
  We consider a class of simplest Majoron models where neutrino- majoron couplings can be in the range $g \sim 10^{-5}-10^{-3}$ leading to the observability of neutrinoless double beta decay with majoron emission. The majoron is a singlet of the electroweak gauge symmetry, thus avoiding conflict with the LEP data on Z decay, which rules out the triplet and doublet majoron models. 
Z Berezhiani, A Yu Smirnov and J W F Valle