Nuclear moments for the neutrinoless double beta decay

Abstract

A derivation of the neutrinoless double beta decay rate, specially adapted for nuclear structure calculations, is presented. It is shown that the Fourier-Bessel expansion of the hadronic currents, jointly with angular momentum recoupling, leads to very simple final expressions for the nuclear form factors. This greatly facilitates the theoretical estimate of the half-life. Our approach does not require the closure approximation, which, however, can be implemented if desired. The method is exemplified for ββ decay 48Ca → 48Ti, both within the QRPA and a shell-model like model.