Analysis of mechanisms that could contribute to neutrinoless double-beta decay (original) (raw)
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Mechanisms of neutrinoless double-beta decay: A comparative analysis of several nuclei
Physics of Atomic Nuclei, 2010
The neutrinoless double beta decay of several nuclei that are of interest from the experimental point of view ( 76 Ge, 82 Se, 100 Mo, 130 Te, and 136 Xe) is investigated on the basis of a general Lorentzinvariant effective Lagrangian describing physics effects beyond the Standard Model. The half-lives and angular-correlation coefficients for electrons are calculated for various decay mechanisms associated, in particular, with the exchange of Majorana neutrinos, supersymmetric particles (with R-parity violation), leptoquarks, and right-handed W R bosons. The effect of theoretical uncertainties in the values of relevant nuclear matrix elements on decay features is considered.
Frontiers in Physics, 2021
Since the experimental discovery of neutrino oscillations, the search for the neutrinoless double beta (0νββ) decay has intensified greatly, as this particular decay mode, if experimentally discovered, could offer a testing ground for Beyond Standard Model (BSM) theories related to the yet hidden fundamental properties of neutrinos and the possibility of violating of some fundamental symmetries. In this work we make a brief review of the nuclear matrix elements and phase space factors calculations performed mainly by our group. Next, using these calculations and the most recent experimental half-life limits, we revise the constraints on the BSM parameters violating the lepton number corresponding to four mechanisms that could contribute to 0νββ decay. Finally, using the values obtained for the BSM parameters from one of the most sensitive double-beta decay experiments, we provide a comparison with the sensitivities of other experiments.
Neutrinoless double beta decay: searching for new physics with comparison of different nuclei
The neutrinoless double beta decay is analyzed using a general Lorentz invariant effective Lagrangian for various decaying nuclei of current experimental interest: 76^{76}76Ge, 82^{82}82Se, 100^{100}100Mo, 130^{130}130Te, and 136^{136}136Xe. We work out the half-lives and angular correlation coefficients of the outgoing electrons in several scenarios for new physics: the left-right symmetric models, the R-parity-violating SUSY and models with leptoquarks. The theoretical uncertainty in the nuclear matrix elements 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.
Shell model calculations for neutrinoless double beta decay
Journal of Physics: Conference Series, 2015
Nuclear matrix elements (NMEs) for neutrinoless double beta decay (0νββ) are computed for the mechanism of exchange of heavy neutrinos. The calculations are performed with a shell model (ShM) code recently developed, for three experimentally interested nuclei, 48 Ca, 76 Ge, and 82 Se. We study the different nuclear effects, such as short range correlations (SRCs), finite nuclear size (FNS) and higher order terms in the nucleon currents (HOC) on the final values of the NMEs, and find that their influence is stronger than in the case of the light neutrino exchange mechanism. We compare our results with similar results from literature and discuss the differences.
Physical Review C, 2018
Weak interaction in nuclei represents a well-known venue for testing many of the fundamental symmetries of the Standard Model. In particular, neutrinoless double-beta decay offers the possibility to test Beyond Standard Model theories predicting that neutrinos are Majorana fermions and the lepton number conservation is violated. This paper focuses on an effective field theory approach to neutrinoless double-beta decay for extracting information regarding the properties of the Beyond Standard Model Lagrangian responsible for this process. We use shell model nuclear matrix elements and the latest experimental lower limits for the half-lives to extract 12 lepton number violating parameters of five nuclei of experimental interest, and lower limits for the energy scales of the new physics. Using the most stringent limits that we obtain for the values of the lepton number violating parameters, we predict new half-life limits for the other nuclei of experimental interest, in the case of 12 neutrino double-beta decay mechanisms. We provide an analysis that could reveal valuable information regarding the dominant neutrinoless double-beta decay mechanism, if experimental half-life data becomes available for different isotopes.
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.
Probing the mechanism of neutrinoless double-beta decay in multiple isotopes
Journal of High Energy Physics
A large experimental program is being mounted to search for neutrinoless double-beta decay over the next decade. Multiple experiments using different target isotopes are being prepared to explore the whole parameter space allowed for inverted-ordered light neutrinos, and have the potential to make discoveries in several other scenarios, including normal-ordered light neutrinos and other exotic mechanisms. We investigate to what extent long-range and exotic short-range contributions may be distinguished by combining measurements of the decay half-life across isotopes in the framework of a global Bayesian analysis. We demonstrate how measurements in two isotopes will constrain the parameter space up to a two-fold degeneracy, and how a further measurement in a third isotope removes such a degeneracy. We also discuss the impact of uncertainties and correlations in nuclear matrix element calculations. Our work motivates an experimental program measuring neutrinoless double-beta decay in ...
Long-range neutrinoless double beta decay mechanisms
Cornell University - arXiv, 2021
Understanding the origin of lepton number violation is one of the fundamental questions in particle physics today. Neutrinoless double beta decay provides a way in which this violation can be tested. In this article, we derive the form of hadronic and leptonic matrix elements for all possible long-range mechanisms of neutrinoless double beta decay. With these, we calculate the numerical values of the nuclear matrix elements (NME) and phase space factors (PSF) by making use of the interacting boson model of the nucleus (IBM-2) for NMEs and of exact Dirac wave functions for the PSFs. We show that: (I) lepton number violation can occur even with zero (or very small) neutrino mass and (II) the angular correlations of the emitted electrons can distinguish between different models of non-standard (NS) mechanisms. We set limits on the coupling constants of some NS models, in particular Left-Right models and SUSY models.
Studying Matrix Elements for the Neutrinoless Double Beta Decay of 150Nd via the
2008
The existence of neutrinoless double beta decay would prove that neutrinos have a Majorana nature and that lepton number is not conserved. To extract information about the neutrino mass scale and hierarchy from 0νβ β decay experimental data, accurate nuclear matrix elements are needed. Such information is also crucial for the design of experiments aimed at detecting neutrinoless double beta decay. Nuclear charge-exchange experiments play an important role in constraining the theories used to predict these matrix elements by providing Gamow-Teller strengths and higher order multipole transition strengths. The charge-exchange group at the NSCL focuses on the measurements of 150 Sm(t, 3 He) 150 Pm* and 150 Nd( 3 He,t) 150 Pm* reactions, which are of relevance for the double beta decay of 150 Nd. The details for the 150 Sm(t, 3 He) 150 Pm* experiment and the upcoming 150 Nd( 3 He,t) 150 Pm* experiment are discussed.