Ruling out the inverted neutrino hierarchy with neutrinoless double beta
decay experiments is possible if a limit on the effective mass below the
minimal theoretically possible value is reached. We stress that this lower
limit depends strongly on the value of the solar neutrino mixing angle: it
introduces an uncertainty of a factor of 2 within its current 3 sigma range. If
an experiment is not background-free, a factor of two in effective mass
corresponds to a combined factor of 16 improvement for the experimental
parameters running time, detector mass, background level and energy resolution.
Therefore, a more precise determination of theta(12) is crucial for the
interpretation of experimental results and the evaluation of the potential and
requirements for future experiments. We give the required half-lifes to exclude
(and touch) the inverted hierarchy regime for all double beta decay isotopes
with a Q-value above 2 MeV. The nuclear matrix elements from 6 different groups
and, if available, their errors are used and compared. We carefully put the
calculations on equal footing in what regards various convention issues. We
also use our compilation of matrix elements to give the reachable values of the
effective mass for a given half-life value.Comment: 26 pages, 6 figures. v2: error corrected (misprint in paper we took a
value from), slightly modifying the result
