Neutrinoless double beta decay in heavy deformed nuclei

Abstract

The zero-neutrino mode of the double beta decay in heavy deformed nuclei is investigated in the framework of the pseudo-SU(3) model, which has provided an accurate description of collective nuclear structure and predicted half-lives for the two-neutrino mode in good agreement with experiments. In the case of 238U the calculated zero-neutrino half-life is at least three orders of magnitude greater than the two-neutrino one, giving strong support of the identification of the radiochemically determined half-life as being the two-neutrino double beta decay. For 150Nd the zero-neutrino matrix elements are of the order of magnitude of, but lesser than, those evaluated using the QRPA. This result confirms that different nuclear models produce similar zero-neutrino matrix elements, contrary to the two-neutrino case. Using these pseudo-SU(3) results and the upper limit for the neutrino mass we estimate the ββ 0 ν half-lives for six nuclei. An upper limit for majoron coupling constant is extracted from the experimental data.