GT neutrino–nuclear responses for double beta decays and astro neutrinos

Ejiri, H.; Suhonen, J.

doi:10.1088/0954-3899/42/5/055201

Cited by 42 publications

(106 citation statements)

References 54 publications

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“…Later, the more comprehensive pnQRPA studies [43][44][45] of Gamow-Teller β decays of a wide range of nuclei (A = 62 − 142) predicted heavily quenched values of g A . These values depend on the mass number A and they are depicted for four separate mass ranges as hatched boxes in Fig.…”

Section: Theoretical Backgroundmentioning

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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Section: Theoretical Backgroundmentioning

confidence: 99%

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

Suhonen

2017

Phys. Rev. C

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“…The half-life of 0νββ decay is proportional to the fourth power of the weak axial-vector coupling constant g A [1,2], but it is not quite clear what value to use for it when calculating theoretical predictions for the decay rates [3,4]. Theoretical predictions for the half-lives are crucial when designing optimal experimental setups to detect 0νββ events.…”

Section: Introductionmentioning

confidence: 99%

“…One alternative is the study of β decays, both allowed and forbidden, since experimental data is available to compare with the calculated physical observables. The related quenching of the computed nuclear matrix elements (NMEs) was addressed already for the allowed Gamow-Teller [4] and first-forbidden [3] transitions in medium-heavy even-mass nuclei. In the present work we extend these studies to first-, second-, third-, fourth-and fifth-forbidden β − decays of odd-mass (odd-A) nuclei by studying the shape evolution of the associated electron spectra and by calculating the involved nuclear matrix elements (NMEs) in the framework of the microscopic quasiparticle-phonon model (MQPM).…”

Section: Introductionmentioning

confidence: 99%

Electron spectra in forbiddenβdecays and the quenching of the weak axial-vector coupling constantgA

2017

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Electron spectra in forbidden β decays and the quenching of the weak axial-vector coupling constant gA Kostensalo, Joel; Haaranen, Mikko; Suhonen, Jouni Kostensalo, J., Haaranen, M., & Suhonen, J. (2017). Electron spectra in forbidden β decays and the quenching of the weak axial-vector coupling constant gA. Physical Review C, 95 (4) Evolution of the electron spectra with the effective value of the weak axial-vector coupling constant g A was followed for 26 first-, second-, third-, fourth-and fifth-forbidden β − decays of odd-A nuclei by calculating the involved nuclear matrix elements (NMEs) in the framework of the microscopic quasiparticle-phonon model (MQPM). The next-to-leading-order terms were included in the β-decay shape factor of the electron spectra. The spectrum shapes of third-and fourth-forbidden nonunique decays were found to depend strongly on the value of g A , while first-and second-forbidden decays were mostly unaffected by the tuning of g A . The g A -driven evolution of the normalized β spectra was found to be quite universal, largely insensitive to the small changes in the nuclear mean field and the adopted residual many-body Hamiltonian producing the excitation spectra of the MQPM. This makes the comparison of experimental and theoretical electron spectra, coined "the spectrum-shape method" (SSM), a robust tool for extracting information on the effective values of the weak coupling constants. In this exploratory work two new experimentally interesting decays for the SSM treatment were discovered: the ground-state-to-ground-state decays of 99 Tc and 87 Rb. Comparing the experimental and theoretical spectra of these decays could shed light on the effective values of g A and g V for second-and third-forbidden nonunique decays. The measurable decay transitions of 135 Cs and 137 Cs, in turn, can be used to test the SSM in different many-body formalisms. The present work can also be considered as a (modest) step towards solving the g A problem of the neutrinoless double beta decay.

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“…Thus it is of great importance to have a good understanding of the value of g A when assessing the potential experimental verification of the neutrinoless mode of double β decay (check, e.g., Refs. [6,7]). …”

Section: Introductionmentioning

confidence: 99%

“…The attempts to probe the value of g A have been done mainly in the context of the proton-neutron quasiparticle random-phase approximation (pnQRPA) [6,7,[9][10][11][12][13], the nuclear shell model (NSM) [14][15][16], and the interacting boson approximation (IBA) [17,18]. These studies have compared the measured data with the corresponding computed observables in the context of allowed and first-forbidden unique β decays, as well as two-neutrino double β decays.…”

Section: Introductionmentioning

confidence: 99%

Forbidden nonuniqueβdecays and effective values of weak coupling constants

2016

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Forbidden nonunique β decays and effective values of weak coupling constantsHaaranen, Mikko; Srivastava, P. C.; Suhonen, Jouni Haaranen, M., Srivastava, P. C., & Suhonen, J. (2016 Forbidden nonunique β decays feature shape functions that are complicated combinations of different nuclear matrix elements and phase-space factors. Furthermore, they depend in a very nontrivial way on the values of the weak coupling constants, g V for the vector part and g A for the axial-vector part. In this work we include also the usually omitted second-order terms in the shape functions to see their effect on the computed decay half-lives and electron spectra (β spectra). As examples we study the fourth-forbidden nonunique ground-state-to-ground-state β − decay branches of 113 Cd and 115 In using the microscopic quasiparticle-phonon model and the nuclear shell model. A striking new feature that is reported in this paper is that the calculated shape of the β spectrum is quite sensitive to the values of g V and g A and hence comparison of the calculated with the measured spectrum shape opens a way to determine the values of these coupling constants. This article is designed to show the power of this comparison, coined spectrum-shape method (SSM), by studying the two exemplary β transitions within two different nuclear-structure frameworks. While the SSM seems to confine the g V values close to the canonical value g V = 1.0, the values of g A extracted from the half-life data and by the SSM emerge contradictory in the present calculations. This calls for improved nuclear-structure calculations and more measured data to systematically employ SSM for determination of the effective value of g A in the future.

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GT neutrino–nuclear responses for double beta decays and astro neutrinos

Cited by 42 publications

References 54 publications

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

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

Electron spectra in forbiddenβdecays and the quenching of the weak axial-vector coupling constantgA

Forbidden nonuniqueβdecays and effective values of weak coupling constants

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