Development and application of nuclear structure models to calculate double beta decay matrix elements
Final Report Abstract
The main conclusions obtained in the present DFG-project can be summarized as follows: By making use of experimental 2vßß decay rates within the QRPA to adjust the most relevant parameter gpp, the calculated Ovßß decay matrix elements get essentially independent of the size of the single-particle basis and of the choice of the residual interaction. Furthermore, the matrix elements also become rather stable with respect to the possible quenching of the axial vector coupling constant gA. This way of fixing gpp within the QRPA is now becoming a standard among the theoretical groups calculating Mov. Furthermore, by allowing for the strong quenching g A < 1, we have shown for the first time that three independent lifetime data 2vßß, EC, ß- (in the cases when all these data exist) can be accurately reproduced by means of two free parameters (gpp, gA). A method to calculate the double beta decay matrix elements M2v and Mov within the continuum-QRPA has been formulated for the first time. As a first step, a version of the cQRPA with nucleon pairing realized only on a discrete basis has been applied. The M2v are almost unaffected when the single-particle continuum is taken into account. In contrast, we find a regular suppression of the Ovßß amplitude that can be associated with additional ground state correlations owing to collective states in the continuum which are naturally described within the cQRPA. Thus, the calculated Mov,s actually provide lower limits for the matrix elements within the cQRPA and it is expected that future inclusion of nucleon pairing in the single-particle continuum will somewhat compensate the observed suppression of Mov values. It will allow to test the stability of the calculated Mov, discussed in the previous paragraph, in the entire single-particle space.
Publications
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Assessment of uncertainties in QRPA 0νββ0νββ-decay nuclear matrix elements. Nuclear Physics A, Vol. 766. 2006, pp. 107–131.
Erratum to: “Assessment of uncertainties in QRPA -decay nuclear matrix elements” [Nucl. Phys. A 766 (2006) 107] Nuclear Physics A, Volume 793.2007, Issues 1–4, pp. 213-215. (Siehe online unter: arXiv:0706.4304 [nucl-th])http://arxiv.org/abs/0706.4304
V. A. Rodin, A. Faessler, F. Simkovic and P. Vogel
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K. Amos, A. Faessler and V. Rodin, Phys. Rev. C 76 (2007). (Siehe online unter: arXiv:nuclth/ 0702016)
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S. Y. Igashov, V. A. Rodin, M. H. Urin and A. Faessler, proceedings of International Conference on Fundamental Problems of Nuclear Physics, Atomic Power Engineering and Nuclear Technologies (Nucleus 2007, Voronezh, Russia, 25-29 Jun 2007). (Siehe online unter: arXiv:0711.4751 [nucl-th])
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V. Rodin and A. Faessler, Phys. Rev. C 77 (2008). (Siehe online unter: arXiv:0707.2742 [nucl-th])
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V. Rodin and A. Faessler, Prog. Part: Nucl. Phys. 57 (2006). (Siehe online unter: arXiv:nucl-th/0602005)
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V. Rodin, A. Faessler, F. Simkovic and P. Vogel, Czech. J. Phys. 56 (2006). (Siehe online unter: arXiv:nucl-th/0503063 ; arXiv:nuclth/ 0602004)
