Double beta decay in the generalized-seniority scheme

We employ a generalized-seniority-based truncation scheme to calculate double beta decay rates in 76Ge, 82Se, 128Te, and 130Te, avoiding problems associated with other shell-model calculations and the quasiparticle random phase approximation (QRPA). Our two-neutrino matrix elements are small, reflecting a suppression mechanism first observed in the QRPA. The new results should be most accurate for neutrinoless decay because the closure approximation is reliable and the matrix elements less suppressed. We set limits on the Majorana mass of the neutrino that differ only by factors of two or three from those of previous methods, suggesting that major difficulties in predicting double beta decay are restricted to the two-neutrino process. (orig.)