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Abstract

We consider the possibility to gain information on the lepton mixing matrix element |U(e3)| from an improved experimental limit on the effective neutrino mass governing neutrino-less double beta decay. We show that typically a lower limit on |U(e3)| can be set. Furthermore, we give the values of the sum of neutrino masses and |U(e3)| which are allowed and forbidden by an experimental upper limit on the effective mass. Alternative explanations for neutrino-less double beta decay or Dirac neutrinos would be required if future measurements showed that the values lie in the respective regions. Moreover, we argue that a measurement of |U(e3)| from neutrino-less double beta decay is very difficult due to the expected errors on the effective mass and the oscillation parameters.