Double beta decay in pn-QRPA model with isospin and SU(4) symmetry constraints

The transition matrix elements for the 0+ → 0+ double beta decays are calculated for 48 Ca, 76 Ge, 82 Se, 90 Mo, 128 Te and 130 Te nuclei, using a δ-interaction. The particle-particle interaction parameters within the T = 1, S = 0 and T = 0, S = 1 channels have been fixed by invoking the isospin and Wigner SU(4) symmetries, respectively. With this recipe, the measured 2ν half lives of 48 Ca, 82 Se, 128 Te and 130 Te, are fairly well reproduced, whereas those of 76 Ge and 90 Mo are overestimated by an order of magnitude. The upper limit for the effective neutrino mass, as obtained from the theoretical estimated of 0ν matrix elements, is < mν >∼ 1 eV. Simple analytic expressions for 0ν and 2ν - ββ moments, in terms of particle-particle interaction parameters, are proposed within the framework of QRPA. (author)