Weak-interaction and nuclear-structure aspects of nuclear double beta decay

Weak-interaction and nuclear-structure aspects of double beta decay are reviewed. Starting from effective electroweak lagrangians, decay rates for the two-neutrino and neutrinoless modes of the nuclear double beta decay transitions are defined and second-order perturbative expressions for the nuclear decay amplitudes are given. Nuclear matrix elements of the relevant operators are presented, as extracted from data and from shell-model and QRPA calculations as well as from other theoretical approximations. The analysis is performed both for the two-neutrino and neutrinoless modes of the decay. The expressions for ground-state-to-ground-state and ground-state-to-excited-state transitions are presented. Updated experimental and theoretical information on beta(-)beta(-) decays in Ca-48, Ge-76, Se-82, Zr-96, Mo-100, Cd-116, Sn-124, Te-128, Te-130, Xe-136, Nd-150, and on beta(+)beta(+), beta(+) EC and double EC decays in Kr-78, Mo-92, Ru-96, Cd-106, Xe-124, Ba-130, Ce-136 is analyzed and compared with theoretical results. The relevance of single-beta-decay transitions feeding some of the nuclei where double-beta-decay transitions occur is pointed out. The systematics of various phase-space factors and extracted matrix elements is presented. (C) 1998 Elsevier Science B.V. All rights reserved