Nuclear matrix elements for Majoron-emitting double- β decay (original) (raw)
Related papers
1997
We have developed a formalism, based on the Fourier-Bessel expansion, that facilitates the evaluation of matrix elements involving nucleon recoil operators, such as appear in serveral exotic forms of neutrinoless double beta decay (ββ 0ν). The method is illustrated by applying it to the "charged" majoron model, which is one of the few that can hope to produce an observable effect. From our numerical computations within the QRPA performed for 76 Ge, 82 Se, 100 Mo, 128 T e and 150 Nd nuclei, we test the validity of approximations made in earlier work to simplify the new matrix elements, showing that they are accurate to within 15%. Our new method is also suitable for computing other previously unevaluated ββ 0ν nuclear matrix elements.
Computation of products of phase space factors and nuclear matrix elements for double beta decay *
Chinese Physics C, 2019
Nuclear matrix elements (NME) and phase space factors (PSF) entering the half-life formulas of the double-beta decay (DBD) process are two key quantities whose accurate computation still represents a challenge. In this study, we propose a new approach of calculating these, namely the direct computation of their product as an unique formula. This procedure allows a more coherent treatment of the nuclear approximations and input parameters appearing in both quantities and avoids possible confusion in the interpretation of DBD data due to different individual expressions adopted for PSF and NME (and consequently their reporting in different units) by different authors. Our calculations are performed for both two neutrino ( ) and neutrinoless ( ) decay modes, for five nuclei of the most experimental interest. Further, using the most recent experimental limits for decay half-lives, we provide new constraints on the light mass neutrino parameter. Finally, by separating the factor represen...
Nuclear matrix elements for neutrinoless double-beta decay and double-electron capture
Journal of Physics G: Nuclear and Particle Physics, 2012
A new generation of neutrinoless double beta decay (0νββ-decay) experiments with improved sensitivity is currently under design and construction. They will probe inverted hierarchy region of the neutrino mass pattern. There is also a revived interest to the resonant neutrinoless doubleelectron capture (0νECEC), which has also a potential to probe lepton number conservation and to investigate the neutrino nature and mass scale. The primary concern are the nuclear matrix elements. Clearly, the accuracy of the determination of the effective Majorana neutrino mass from the measured 0νββ-decay half-life is mainly determined by our knowledge of the nuclear matrix elements. We review recent progress achieved in the calculation of 0νββ and 0νECEC nuclear matrix elements within the quasiparticle random phase approximation. A considered self-consistent approach allow to derive the pairing, residual interactions and the two-nucleon short-range correlations from the same modern realistic nucleon-nucleon potentials. The effect of nuclear deformation is taken into account. A possibility to evaluate 0νββ-decay matrix elements phenomenologically is discussed.
Neutrinoless Double Beta Decay The Nuclear Matrix Elements Revisited
Journal of Physics: Conference Series, 2011
We explore the influence of the deformation on the nuclear matrix elements of the neutrinoless double beta decay (NME), concluding that the difference in deformation-or more generally in the amount of quadrupole correlations-between parent and grand daughter nuclei quenches strongly the decay. We correlate these differences with the seniority structure of the nuclear wave functions. In this context, we examine the present discrepancies between the NME's obtained in the framework of the Interacting Shell Model and the Quasiparticle RPA. In our view, part of the discrepancy can be due to the limitations of the spherical QRPA in treating nuclei which have strong quadrupole correlations. We surmise that the NME's in a basis of generalized seniority are approximately model independent, i. e. they are "universal". We discuss as well how varies the nuclear matrix element of the 76 Ge decay when the wave functions of the two nuclei involved in the transition are constrained to reproduce the experimental occupancies. In the Interacting Shell Model description the value of the NME is enhanced about 15% compared to previous calculations, whereas in the QRPA the NME's are reduced by 20%-30%. This diminishes the discrepancies between both approaches. In addition, we update the effects of the short range correlations on the NME's in the light of the recently proposed parametrizations obtained by renormalizing the 0νββ transition operator at the same footing than the effective interaction.
Anatomy of nuclear matrix elements for neutrinoless double-beta decay
Arxiv preprint arXiv: …, 2007
Abstract: We show that, within the Quasiparticle Random Phase Approximation (QRPA) and the renormalized QRPA (RQRPA) based on the Bonn CD nucleon-nucleon interaction, the competition between the pairing and the neutron-proton particle-particle and particle-hole ...
Theoretical bounds for majoron emission from nuclear double-beta decay processes
Journal of Physics G: Nuclear and Particle Physics, 1994
Theoretical upper limits for the neutrino-majoron coupling constant, g , ace exbacted from a systematic calculation of neutrinoless double-beta decay rates for ansitions in %a, '"e, 82Se. '18Te, I3OTe and 136Xe. The nuclear wavefunctions which we have used to compute the theoretical bounds on g have been tested in calculatians involving two-neutrino m d neuainoless double-beta decay rates. The resulting value is of the order of 6 % in good agreement with recently reponed data by lhe Heidelberg-Moscow-LNGS collabomtion.
Charged majoron emission in neutrinoless double beta decay
1996
We examine in detail the predictions of the charged majoron model, introduced recently by Burgess and Cline, for 0 + ! 0 + transitions. The relevant n uclear matrix elements are evaluated, within the quasiparticle random phase approximation, for 76 Ge, 82 Se, 100 Mo, 128 Te and 150 Nd nuclei. The calculated transition rates turn out to be much smaller than the experimental upper limits on possible majoron emission, except in a small region of the model's parameter space.
Arbitrary mass Majorana neutrinos in neutrinoless double beta decay
Physical Review D, 2014
We revisit the mechanism of neutrinoless double beta (0νββ) decay mediated by the exchange with the heavy Majorana neutrino N of arbitrary mass mN, slightly mixed ∼ UeN with the electron neutrino νe. By assuming the dominance of this mechanism, we update the well-known 0νββ-decay exclusion plot in the mN − UeN plane taking into account recent progress in the calculation of nuclear matrix elements within quasiparticle random phase approximation and improved experimental bounds on the 0νββ-decay half-life of 76 Ge and 136 Xe. We also consider the known formula approximating the mN dependence of the 0νββ-decay nuclear matrix element in a simple explicit form. We analyze its accuracy and specify the corresponding parameters, allowing one to easily calculate the 0νββ-decay half-life for arbitrary mN for all the experimentally interesting isotopes without resorting to real nuclear structure calculations.
2016
We analyze the effects that different nuclear structure approximations associated with the short range correlations (SRC), finite nucleon size (FNS), higher order terms in the nucleon currents (HOC) and with some nuclear input parameters, have on the values of the nuclear matrix elements (NMEs) for the neutrinoless double beta (0νββ) decay. The calculations are performed with a new Shell Model(ShM) code which allows a fast computation of the two-body matrix elements of the transition operators. The treatment of SRC, FNS and HOC and the use of quenched or unquenched values for the axial vector coupling constant produces the most important effects on the NMEs values. Equivalent effects of some of these approximations are also possible, which may lead (accidentally) to close final results. We found that the cumulative effect of all these nuclear ingredients on the calculated nuclear matrix elements NMEs is significant. Since the NMEs values are often obtained with different approximations and/or with different input parameters, a convergent view point on their inclusion/neglecting and an uniformization of the calculations are needed, in order to enter in an era of precision concerning the computation of the NMEs for double beta decay.
Calculation of Nuclear Matrix Elements for the Two-Neutrino Double Beta Decay of128,130Te Isotopes
2005
Bu calismada,128,130 Te izotoplarinin iki-notrinolu cift bozunumu (2νββ) icin nukleer matris elemanlari,yuk alisverisli etkilesmeyi parcacik-desik kanalinda dikkate alarak, Tamm-Dancoff Yaklasimi’nin (TDA) eziduler teoremiyle birlikte kullanilmasiyla hesaplandi. Hesaplamalar, kuresel cekirdek durumunda, Hartre Fock Yaklasimi’ni Sykrme-III kuvvetleri ile birlikte kullanarak elde edilen tek parcacik enerjileri bazinda yapildi.. Elde edilen sonuclar bu tip tek parcacik bazinin cift beta bozunumu nukleer matris elemani hesabinda alternatif bir yaklasim olarak kullanilabilecegini gostermektedir.