Constraints on Neutrino Mixing Parameters By Observation of Neutrinoless   Double Beta Decay
  Assuming positive observation of neutrinoless double bata decay together with the CHOOZ reactor bound, we derive constraints imposed on neutrino mixing parameters, the solar mixing angle \theta_{12} and the observable mass parameter < m >_{\beta} in single beta decay experiments. We show that 0.05 eV < < m >_{\beta} < 2 eV at the best fit parameters of the LMA MSW solar neutrino solution by requiring the range of the parameter < m >_{\beta \beta} deduced from recently announced double beta decay events at 95 % CL with +/- 50 % uncertainty of nuclear matrix elements. 
Hisakazu Minakata and Hiroaki Sugiyama (Tokyo Metropolitan U.)