Generator Coordinate Method framework for Double Beta Decay
  We propose a consistent prescription for the derivation of the particle number and angular momentum projected QRPA (PQRPA) equation in the Generator Coordinate Method (GCM) framework for calculation of NME's of double-beta decay of axially deformed nuclei. We derive closed formulae for the calculation of excitation energies and wave functions of the intermediate nucleus. 
Andrzej Bobyk, Wies{\l}aw A. Kami\'nski
nucl-th