Effects of perturbation of the transition operator in double-β decay on nuclear matrix elements, effective axial-vector current coupling, and half-life

AbstraktAbstract

We calculate the nuclear matrix element (NME), effective axial-vector current coupling geffA, and half-life of double-β (ββ) decay using the transition operator perturbed by the nuclear interaction. The correction terms for the NME are obtained by extending the hadron sector to a higher order in terms of the Rayleigh-Schrödinger perturbation theory. The NME calculations are performed for the neutrinoless ββ (0vββ) and the two-neutrino ββ (2vββ) decays of 136Xe. The nuclear wave functions are calculated by the quasiparticle random-phase approximation (QRPA) with the Skyrme, the Coulomb, and the contact pairing interactions. Sufficiently large single-particle valence spaces are used. The correction terms for the NME are comparable with the leading term in absolute value, and the sum of the corrections has the opposite sign compared to that of the leading term. The geff A's for the ββ NME are calculated by a few methods depending on the truncation of the NME and the half-life referred to. Similarities are found between some of these geffA's, including those of the 0vββ NME. This leads to the conclusion that the value of geff A can indeed be determined by the perturbed transition operator. It is in a comparable range of the gA for the 2vββ NME. The perturbation effect on the 2vββ half-life is discussed by comparing the calculated half-lives with the different gA's and the NME components.

We calculate the nuclear matrix element (NME), effective axial-vector current coupling geffA, and half-life of double-β (ββ) decay using the transition operator perturbed by the nuclear interaction. The correction terms for the NME are obtained by extending the hadron sector to a higher order in terms of the Rayleigh-Schrödinger perturbation theory. The NME calculations are performed for the neutrinoless ββ (0vββ) and the two-neutrino ββ (2vββ) decays of 136Xe. The nuclear wave functions are calculated by the quasiparticle random-phase approximation (QRPA) with the Skyrme, the Coulomb, and the contact pairing interactions. Sufficiently large single-particle valence spaces are used. The correction terms for the NME are comparable with the leading term in absolute value, and the sum of the corrections has the opposite sign compared to that of the leading term. The geff A's for the ββ NME are calculated by a few methods depending on the truncation of the NME and the half-life referred to. Similarities are found between some of these geffA's, including those of the 0vββ NME. This leads to the conclusion that the value of geff A can indeed be determined by the perturbed transition operator. It is in a comparable range of the gA for the 2vββ NME. The perturbation effect on the 2vββ half-life is discussed by comparing the calculated half-lives with the different gA's and the NME components.