Neutrinoless double-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>decay of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>48</mml:mn></mml:msup></mml:math>Ca in the shell model: Closure versus nonclosure approximation

Sen'kov, R. A.; Horoi, Mihai

doi:10.1103/physrevc.88.064312

Cited by 89 publications

(189 citation statements)

References 25 publications

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“…Expressions for the Gamow-Teller (GT), the Fermi (F), and the tensor (T) cases are described in detail in Refs. [11,14]. The other three potentials are presented here in a form similar to Eq.…”

Section: Discussionmentioning

confidence: 99%

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Analysis of mechanisms that could contribute to neutrinoless double-beta decay

Horoi

Neacsu

2016

Phys. Rev. D

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Neutrinoless double-beta decay, is a beyond the Standard Model process that would indicate that neutrinos are Majorana fermions and the lepton number is not conserved. It could be interesting to use the neutrinoless double-beta decay observations to distinguish between several beyond Standard Model mechanisms that could contribute to this process. Accurate nuclear structure calculations of the nuclear matrix elements necessary to analyze the decay rates could be helpful to narrow down the list of contributing mechanisms. We investigate the information one can get from the angular and energy distribution of the emitted electrons, and from the half-lives of several isotopes, assuming that the right-handed currents exist. For the analysis of these distributions we calculate the necessary nuclear matrix elements using shell model techniques, and we explicitly consider interference terms.

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Section: Discussionmentioning

confidence: 99%

“…[7] shows some of these NME for isotopes of immediate experimental relevance. Here we describe the status of the shell model calculations of these NME [6][7][8][9][10][11][12][13][14][15], and their relevance for discriminating possible competing mechanisms that may contribute to the neutrinoless double-beta decay process.…”

Section: Introductionmentioning

confidence: 99%

Analysis of mechanisms that could contribute to neutrinoless double-beta decay

Horoi

Neacsu

2016

Phys. Rev. D

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“…However, there exists a non-closure calculation in the framework of the ISM in [57] for the 0νββ decay of the light nucleus 48 Ca.…”

Section: Nuclear Model and The Two-stage Fitting Proceduresmentioning

confidence: 99%

Impact of the quenching of gA on the sensitivity of 0νββ experiments

Suhonen

2017

Phys. Rev. C

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Detection of the neutrinoless ββ (0νββ) decay is of high priority in the particle-and neutrinophysics communities. The detectability of this decay mode is strongly influenced by the value of the weak axial-vector coupling constant gA. The recent nuclear-model analyses of β and ββ decays suggest that the value of gA could be dramatically quenched, reaching ratios of g free A /gA ≈ 4, where g free A = 1.27 is the free, neutron-decay, value of gA. The effects of this quenching appear devastating for the sensitivity of the present and future 0νββ experiments since the 4th power of this ratio scales the 0νββ half-lives. This, in turn, could lead to some two orders of magnitude less sensitivity for the 0νββ experiments. In the present article it is shown that by using a consistent approach to both the two-neutrino ββ and 0νββ decays by the proton-neutron quasiparticle random-phase approximation (pnQRPA), the feared two-orders-of-magnitude reduction in the sensitivity of the 0νββ experiments actually shrinks to a reduction by factors in the range 2 − 6. This certainly has dramatic consequences for the potential to detect the 0νββ decay.PACS numbers: 21.60.Jz, 23.40.Hc, 27.50.+e, 27.60.+j Keywords: Detectability of the neutrinoless double beta decay, nuclear matrix elements, quenching of the axial-vector coupling strength, sensitivity of the double-beta experiments

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“…The neutrino potentials depend on the relative distance between the two decaying nucleons, r, the mass number A, and the closure energy µ. The radial forms are given explicitly [10]. For the heavy-neutrino exchange, the potential does not depend on µ and it looks like a smeared-out delta function [1], [5].…”

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confidence: 99%

“…[10], [11] and references therein) that these energies are small compared to the neutrino exchange energy, and therefore the widely used closure approximation replaces these energies by a constant value and sums-out the contribution of the intermediate states. It was shown [10], [12], [11] that this approximation provides matrix elements about 10% smaller, but we recently found [10], [12] optimal closure energies for which the nuclear matrix elements in both approaches are the same (see e.g. Fig.…”

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confidence: 99%

Nuclear Structure Aspects of Neutrinoless Double-βDecay

2014

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We decompose the neutrinoless double-beta decay matrix elements into sums of products over the intermediate nucleus with two less nucleons. We find that the sum is dominated by the J π = 0 + ground state of this intermediate nucleus for both the light and heavy neutrino decay processes. This provides a new theoretical tool for comparing and improving nuclear structure models. It also provides the connection to two-nucleon transfer experiments.PACS numbers: 23.40. Bw, 21.60.Cs, 23.40.Hc, 14.60.Pq Neutrinoless double beta decay 0νββ is one of the most important current topics in physics that provides unique information on the neutrino properties [1], [2], [3]. The 0νββ decay process and the associated nuclear matrix elements (NME) were investigated by using several approaches including the quasiparticle random phase approximation (QRPA) [1], the interacting shell model [4], [5], the interacting boson model [6], [7], the generator coordinate method [8], and the projected Hartree-Fock Bogoliubov model [9]. It is critical to assess which nuclei are the best candidates for experimental study.Since the experimental decay rate is proportional to the square of the calculated nuclear matrix elements, it is important to calculate these matrix elements with high accuracy to be able to extract the neutrino effective mass which can be used to determine the absolute scale of neutrino masses. However, the theoretical methods used give results that differ from one another by factors of up to 2-3. It is important to understand the nuclear structure aspects of these matrix elements and why the models give differing results. In this Letter we present a new theoretical tool for understanding 0νββ matrix elements by expanding them in terms of a summation over states in the nucleus with two less nucleons (A − 2). We show that the matrix elements are dominated by the contribution through the ground state of the (A − 2) intermediate nucleus. We also show that the lightneutrino matrix elements are dominated by the GamowTeller type operator that is proportional to a schematic interaction of the form σ 1 · σ 2 /r. This opens up new ways of comparing theoretical models and improving the accuracy of the NME for 0νββ decay.The 0νββ process can be naturally described in 2 nd order perturbation theory, in which the energies of the virtual states of the intermediate nucleus obtained by a single beta decay of the parent nucleus enter into the propagator. However, it has been known for some time (see e.g. [10], [11] and references therein) that these energies are small compared to the neutrino exchange energy, and therefore the widely used closure approximation replaces these energies by a constant value and sums-out the contribution of the intermediate states. We will start with the case for the 0νββ decay of 76 Ge that is shown in Fig. 1. Previously, the structure dependence has been analyzed in terms of the "chargeexchange" to intermediate states in 76 As. In contrast, we will show the results for expanding in terms of the intermediate stat...

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Neutrinoless double-βdecay of48Ca in the shell model: Closure versus nonclosure approximation

Cited by 89 publications

References 25 publications

Analysis of mechanisms that could contribute to neutrinoless double-beta decay

Analysis of mechanisms that could contribute to neutrinoless double-beta decay

Impact of the quenching of gA on the sensitivity of 0νββ experiments

Nuclear Structure Aspects of Neutrinoless Double-βDecay

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