Measurement of the ββ2ν decay of 76Ge

Balysh, A.; Beck, M.; Belyaev, S. T.; Bensch, F.; Bockholt, J.; Demehin, A.; Gurov, A.A.; Heusser, G.; Klapdor‐Kleingrothaus, H. V.; Kondratenko, I.P.; Kotelnikov, D. V.; Lebedev, V. I.; Maier, B.; Müller, Axel; Petry, F.; Piepke, A.; Pronsky, A.; Strecker, H.; Völlinger, M.; Zuber, Κ.

doi:10.1016/0370-2693(94)91103-7

Cited by 34 publications

(20 citation statements)

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“…The coefficients of the decay rate formula derived from the OEM + QRPA calculation are similar to those obtained previously [15], and, combined with experimental data [33], lead to sharp limits on the effective neutrino mass and right-handed parameters, it seems after all that neutrinoless double beta decay remains a sensitive tool to probe physics beyond the standard model. This study is supported in part by a Grant-in-Aid for Scientific Research (05243204) from the Ministry of Education, Science and Culture (Monbusho).…”

Section: Discussionmentioning

confidence: 66%

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Extended operator expansion method for neutrinoless double beta decay

Hirsch

Kadowaki

Klapdor‐Kleingrothaus

et al. 1995

Z. Physik A - Hadrons and Nuclei

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Abstract. Reliable calculations of nuclear matrix elements are a prerequisite for the determination of the effective neutrino mass and other particle physics parameters from neutrinoless double beta decay. Here, the operator expansion method is improved by including Coulomb, tensor and central interactions simultaneously. Furthermore, the formalism of the OEM is extended to those matrix elements necessary to extract the right-handed parameters (2) and (r/) from Ovflfl decay. OEM includes the dependence of the nuclear matrix elements on the intermediate states implicitly and can therefore be understood as a step beyond the closure approximation. Numerical studies are carried out for the isotope 76Ge combining the OEM expressions with ground-state wave functions calculated within a proton-neutron quasiparticle Random Phase Approximation (pn-QRPA) model. The influence and relative importance of central, tensor and Coulomb interactions is investigated. Within the OEM, contributions from the Coulomb force are found to be negligible in Ovflfi decay, while the tensor force leads to a moderate change of the results, of the order of (10-30) %, giving a better agreement between sets of calculations which employ different NN-interactions. Generally, results of the OEM + QRPA calculation are similar to previous calculations of Ovflfl decay matrix elements, indicating that Ovfifl decay is not sensitive to model approximations and might therefore be more accurately calculated than the strongly suppressed 2vfifi decay matrix elements.

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Section: Discussionmentioning

confidence: 66%

“…Due to the similarity of the matrix elements, naturally also the decay rate coefficients are found to be very close to each other. Taking the lower limit of the 0v/3/3 decay half-life for 76Ge [33], the following upper limits for ( my ), ( 2 ) …”

Section: Numerical Resultsmentioning

confidence: 99%

Extended operator expansion method for neutrinoless double beta decay

Hirsch

Kadowaki

Klapdor‐Kleingrothaus

et al. 1995

Z. Physik A - Hadrons and Nuclei

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“…3). Our results are 0.12 6 0.07 and 0.12 6 0.06 MeV 21 , respectively (a combined value of 0.12 6 0.05 MeV 21 ), while the experimental value of this matrix element (using g A 1.26) is 0.14 6 0.01 MeV 21 [5]. However, shell model calculations of ordinary b decay consistently suggest that g A is renormalized to 1.0 in the nuclear medium [4], in which case the experimental matrix element is 0.…”

mentioning

confidence: 78%

“…We first calculate the decay of 48 Ca in the complete pf shell and validate our method against direct diagonalization. We then present results for the decay of 76 Ge, one of the few nuclei where the 2nbb decay has been precisely measured and where the best limits on the 0n decay have been obtained [5]. Our calculation in the complete ͑0f 5͞2 , 1p, 0g 9͞2 ͒ orbitals, which is impractical using traditional shell model methods, is the first of 2nbb decay in such a large model space.…”

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confidence: 99%

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Shell Model Monte Carlo Method for Two-Neutrino Double Beta Decay

et al. 1996

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Shell model Monte Carlo techniques are used to calculate two-neutrino double beta decay matrix elements. We test the approach against direct diagonalization for 48 Ca in the complete pf shell using the KB3 interaction. The method is then applied to the decay of 76 Ge in the ͑0f 5͞2 , 1p, 0g 9͞2 ͒ model space using a newly calculated realistic interaction. Our result for the matrix element is 0.12 6 0.05 MeV 21 , in reasonable agreement with the experimental value.PACS numbers: 21.60. Cs, 21.60.Ka, 27.40.+z, The double beta (bb) decay of a nucleus is a rare second order weak process [1,2]. The as-yet unobserved neutrinoless mode is of fundamental interest, as it would signal a neutrino mass, lepton number nonconservation, or admixtures of right handed weak currents. In contrast, the existence of the 2n mode has been firmly established (see the review in Ref. [2]). The ability to accurately describe this latter process is an important element in the interpretation of limits on neutrinoless decays. Unfortunately, it seems that 2n matrix elements are highly suppressed and so depend sensitively on small, poorly determined parts of the nuclear wave functions.Most recent calculations of 2nbb matrix elements for nuclei heavier than 48 Ca rely on the quasiparticle random phase approximation (QRPA) [2]. While this approach is computationally simple and includes many features of the two-body interaction known to be relevant for bb decay, the calculated matrix elements are uncertain because of their great sensitivity to the J 1 1 , T 0 particleparticle interaction [3]. The interacting shell model offers a more microscopic approach to the problem. Complete 0hv shell model calculations [4] not only recover more quenching of Gamow-Teller (GT) transitions than QRPA calculations, but also are in agreement with observations (after the universal renormalization of g A to 1.0). However, computational limitations have restricted shell model calculations of the 2nbb decay matrix element to 48 Ca, the lightest of all bb candidates.In this Letter we show how shell model Monte Carlo (SMMC) methods can be used to calculate 2nbb decay matrix elements. We first calculate the decay of 48 Ca in the complete pf shell and validate our method against direct diagonalization. We then present results for the decay of 76 Ge, one of the few nuclei where the 2nbb decay has been precisely measured and where the best limits on the 0n decay have been obtained [5]. Our calculation in the complete ͑0f 5͞2 , 1p, 0g 9͞2 ͒ orbitals, which is impractical using traditional shell model methods, is the first of 2nbb decay in such a large model space.The 2nbb matrix elements between the 0 1 ground states of the initial and final even-even nuclei is given by [6]Here, j0 ͘ and E an average energy denominator. As there is no prescription for choosing the average energy denominator (and even the closure matrix element is usually calculated in a severely truncated basis), the uncertainty in this approximation is difficult to estimate.To calculate the exact 2nbb...

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Radioisotopes

Helmer

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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Radioisotopes, also called nuclides or radionuclides, are not stable, but rather decay to more stable elements or other atoms by emission of high energy radiation. Study of radioisotopes has led to increased understanding of the forces of nature, especially those forces such as those prevalent in nuclei binding exhibited solely in the microscopic world. Naturally occurring radioisotopes are used to determine the ages of materials, as radiopharmaceuticals or radiation sources or tracers in medicine, for nondestructive evaluation, for the tracking of groundwater or air flow, and for scientific analysis. The nuclear physic properties of radioisotopes and the various radiation particles are summarized, including half‐lives, decay constants, angular momentum, and parities. The modes of nuclear decay and the accompanying radiation are described, as are combined nuclear and atomic processes, and atomic decays and corresponding radiations. Decay data for useful radioisotopes are given.

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Measurement of the ββ2ν decay of 76Ge

Cited by 34 publications

References 11 publications

Extended operator expansion method for neutrinoless double beta decay

Extended operator expansion method for neutrinoless double beta decay

Shell Model Monte Carlo Method for Two-Neutrino Double Beta Decay

Radioisotopes

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