Decay Half-lives Research Articles

Neutrino masses and mass hierarchy: evidence for the normal hierarchy

The latest cosmological constraints on the sum of neutrino masses, in combination with the latest laboratory measurements on oscillations, provide “decisive” Bayesian evidence for the normal neutrino mass hierarchy. We show that this result holds across very different prior alternatives by exploring two extremes on the range of prior choices. In fact, while the specific numerical value for the Evidence depends on the choice of prior, the Bayesian odds remain greater than 140:1 across very different prior choices. For Majorana neutrinos this has important implications for the upper limit of the neutrino-less double beta decay half life and thus for the technology and resources needed for future double beta decay experiments.

A focus on selected perspectives of the NUMEN project

The use of double charge exchange reactions is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay half-life. The strategy adopted in the experimental campaigns performed at INFN - Laboratori Nazionali del Sud and in the analysis methods within the NUMEN project is briefly described, emphasizing the advantages of the multi-channel approach to nuclear reaction data analysis. An overview on the research and development activities on the MAGNEX magnetic spectrometer is also given, with a focus on the chosen technological solutions for the focal plane detector which will guarantee the performances at high-rate conditions.

Theoretical calculations of the alpha decay half-lives of 166−190Pt

Calculations of the α-decay half-lives of Pt isotopes have been carried out using the modified Gamow-like model (MGLM) and deformed Woods-Saxon potential model. In order to see the effect of using deformed nuclear potential on the α-decay half-lives of the Platinum isotopes, the spherical Woods-Saxon potential has also been employed in the computation. When compared with experimental data, all the modelsgive very good descriptions of the experimental half-lives. The comparison also suggests that the calculated half-lives considering deformation give better agreement with the experimental data than the results using spherical configuration. New parameter values were obtained for the MGLM model (termed MGLM2). The MGLM2 model gives better descriptions of the half-lives than the MGLM1 model.

Clustering effect in description of the alpha and heavier decay half-life

We examine the alpha and heavier cluster decay half-lives of the nuclei for 87 ≤ Z ≤ 96 using the analytical formula obtained by the Wentzel-Kramers-Brilliouin (WKB) method within the framework of the cluster model for the modified harmonic oscillator and spherical Coulomb potential. We correlate the clustering effect in the nuclei with the nuclear potential depth only and systematically investigate the alpha and heavier cluster decay half-lives. In addition to half-lives, the branching ratios relative to alpha decay half-lives are also calculated and results are compared with experimental data. The rms deviations of the alpha and cluster decay half-lives show a good agreement with the universal decay law (UDL), Horoi and one single line of universal (UNIV) curve models. Utilizing the optimized cluster model parameters, we also predict the half-lives of 14C, 20O, 24,25Ne, 28,30Mg and 32Si cluster emissions from various isotopes for guiding future experiments.

Decay Characteristics of Neutron Excess Silicon Nuclei

In neutron star mergers, neutron excess nuclei and the r-process are important factors governing the production of heavier nuclear systems. A single-particle model evaluation of silicon nuclei suggests that the heaviest Z = 14 nucleus will have mass 54 with filling of the 1f5/2 neutron shell. A = 43 – 54 silicon isotopes have limited experimental half-life data, but the model predicts beta decay half-lives in the range of 0.442 – 8.06 ms. Based on previous calculations for Z = 9 -13, 20, 26, and 30 systems and comparisons to the 43Si, 44Si, 46Si, and 48Si calculations, summarized in the Japanese Nuclear Data Compilation, the single-particle model results likely overestimate the half-lives of A = 43 – 54 neutron excess silicon nuclei.

Nonlocality effect in α decay of heavy and superheavy nuclei

The $\ensuremath{\alpha}$-decay half-life of heavy and superheavy nuclei has been investigated using a potential barrier penetration model that adapts semiclassical WKB calculations to incorporate a coordinate-dependent effective mass for the $\ensuremath{\alpha}$ particle. This effect is a consequence of a dynamic property of nonlocality in the particle-nucleus interaction, as implemented in the barrier tunneling calculations of [N. Teruya, S. B. Duarte, and M. M. N. Rodrigues, Phys. Rev. C 93, 024606 (2016)]. Calculations have been performed for a recent set of experimental data of 255 $\ensuremath{\alpha}$-emitting nuclides, all selected with angular momentum $\ensuremath{\ell}=0$ experimentally assigned. Results show a good agreement when compared to experimental half-life data, obtaining a standard deviation of $\ensuremath{\sigma}=0.306$ and fully satisfying the universal systematics, namely, new universal plot and universal decay law systematics, of $\ensuremath{\alpha}$ decay. Additionally, the present model has been applied to make half-life predictions for 34 possible new $\ensuremath{\alpha}$-decay cases.

Favored α -decay half-lives of odd- A and odd-odd nuclei using an improved density-dependent cluster model with anisotropic surface diffuseness

We extend the improved density-dependent cluster model (DDCM+) of our recent work [Wang et al., Phys. Rev. C 105, 024327 (2022)] to study the favored $\ensuremath{\alpha}$ decays of odd-$A$ and odd-odd nuclei with $Z\ensuremath{\geqslant}82$. In this work, the effective $\ensuremath{\alpha}$-core interactions are determined using the double-folding potential with a realistic M3Y-Reid nucleon-nucleon interaction plus proton-proton Coulomb interaction, in which a deformation-dependent diffuseness correction is validated to address the surface anisotropy and polarization effects in nucleon density distribution. It is found that calculations within the anisotropic diffuseness would yield longer calculated $\ensuremath{\alpha}$ decay half-lives and suggest larger estimated $\ensuremath{\alpha}$-preformation factors, which is quite consistent with the conclusions obtained for the even-even $\ensuremath{\alpha}$ emitters. Meanwhile, the theoretical half-lives agree very well with the experimental data for the favored $\ensuremath{\alpha}$ decays of the odd-$A$ and odd-odd nuclei with a mean factor of 1.94 and 1.61, respectively. Remarkably, the experimental $\ensuremath{\alpha}$-decay half-life of the new thorium isotope $^{207}\mathrm{Th}$ [Yang et al., Phys. Rev. C 105, L051302 (2022)] is also well reproduced with a factor of about 2.50. Furthermore, we present the quantitative predictions on the favored $\ensuremath{\alpha}$-decay half-lives of $^{293,294}119$ and $^{294,295}120\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}$-decay chains in this work, which are expected to serve as useful references for the synthesis of new isotopes in the future.

Calculation of β -decay half-lives within a Skyrme-Hartree-Fock-Bogoliubov energy density functional with the proton-neutron quasiparticle random-phase approximation and isoscalar pairing strengths optimized by a Bayesian method

Background: For data on radioactive nuclei, $\ensuremath{\beta}$ decay provides some of the most important information, applicable to various fields. However, some $\ensuremath{\beta}$-decay data are not available due to experimental difficulties. For this reason, theoretically calculated results have been embedded in the data on radioactive nuclear $\ensuremath{\beta}$ decay to compensate for the missing information.Purpose: It is necessary to treat various nuclear correlations as precisely as possible for theoretical $\ensuremath{\beta}$-decay calculations. In particular, the pairing correlation is one of the most important factors for reproducing $\ensuremath{\beta}$-decay half-lives correctly. Therefore, we first study the effect of zero- and finite-range isovector pairings on half-lives. Second, we investigate the isoscalar pairing strengths, which are determined through experimental data of half-lives. Finally, we predict the isoscalar pairing strengths and half-lives of neutron-rich nuclei.Methods: To calculate the $\ensuremath{\beta}$-decay half-lives, a proton-neutron quasiparticle random-phase approximation on top of a Skryme energy density functional is applied with an assumption of spherical symmetry. The half-lives are calculated by including the allowed and first-forbidden transitions. The isoscalar pairing strength is estimated by a Bayesian neural network (BNN). We verify the predicted isoscalar pairing strengths by preparing the training data and test data.Results: It was confirmed that the finite-range isovector pairing ensures that the $\ensuremath{\beta}$-decay half-lives are insensitive to the model space, while the zero-range one is largely dependent on it. The half-lives calculated with the BNN isoscalar pairing strengths reproduced most of the experimental data, although those of highly deformed nuclei were underestimated. We also studied the predictive performance on new experimental data that were not used for the BNN training and found that they were reproduced well.Conclusions: Our study demonstrates that the isoscalar pairing strengths determined by the BNN can reproduce experimental data with the same accuracy as other theoretical works. To achieve a more precise prediction, the nuclear deformation is important.

Macroscopic–microscopic calculations of the ground state properties of Z = 120 isotopes and their α-decay chains

One of the substantial successes achieved in nuclear physics in the last two decades was the synthesis of dozens of isotopes of new elements up to [Formula: see text]Og, which closed the seventh row of the periodic table and inspired the ambition of adding more elements. This work aims to study extensively the ground state structure and decay properties of proposed [Formula: see text] isotopes. We employed Macroscopic–microscopic scheme based on the Skyrme energy density functional, the Woods–Saxon single-particle potential and Strutinsky’s method to find the structure properties, in a multidimensional deformation space. The same nucleon–nucleon potential is used to find the [Formula: see text]-decay half-life, within the Preformed Cluster Model. For 45 [Formula: see text]120 isotopes, the total energy surfaces, ground state masses, binding energy, deformations and fissionability are determined. The [Formula: see text]-values of the different competing decays and [Formula: see text]-decay half-lives are investigated based on the obtained structure. The results indicate the [Formula: see text]120 isotopes to be the most bound among the studied isotopes. The smallest fission barriers are indicated for the [Formula: see text]120 isotopes. The [Formula: see text]120 isotopes showed the longer half-lives against [Formula: see text]-decay, with an order of [Formula: see text]. The longest half-lives are estimated for the [Formula: see text]120 ([Formula: see text] and [Formula: see text]120 ([Formula: see text] isotopes. The longest full decay chain ending with the stable [Formula: see text]Pb nucleus is anticipated for the [Formula: see text]120 isotope. The shortest decay chain of [Formula: see text]120 terminates after three [Formula: see text]-decays by the spontaneous fission of [Formula: see text]Fl.

Nuclear 0ν2β decays in B-L symmetric SUSY model and in TeV scale left–right symmetric model

In this paper, we take the B-L supersymmetric standard model (B-LSSM) and TeV scale left–right symmetric model (LRSM) as two representations of the two kinds of new physics models to study the nuclear neutrinoless double beta decays (0ν2β) so as to see the senses onto these two kinds of models when the decays are taken into account additionally. Within the parameter spaces allowed by all the existing experimental data, the decay half-life of the nucleus 76Ge and 136Xe, (76Ge, 136Xe), is precisely calculated and the results are presented properly. Based on the numerical results, we conclude that there is greater room for LRSM type models than for B-LSSM type models in foreseeable future experimental observations on the decays.

Predictive power of theoretical models in cluster radioactivity

Many microscopic and macroscopic models are available in the literature to study the cluster radioactivity. The investigation of appropriate theoretical model to study the cluster decay process is an important aspect. We studied cluster-decay in the atomic and mass number range [Formula: see text] and [Formula: see text] using modified generalized liquid drop model (MGLDM), Coulomb and proximity potential model (CPPM) and generalized liquid drop model (GLDM). The results obtained using macroscopic models are compared with that of microscopic models. There are various mass excess tables available in the literature. But indentification of suitable mass excess table for cluster radioactivity is an also important part of this study. The macroscopic models, such as MGLDM, CPPM and GLDM, were used to analyze cluster-decay half-lives. Along with this, microscopic and semi-empirical relations were also investigated. The standard deviation is evaluated in macroscopic, microscopic and semi-empirical formulae. A detailed investigation shows that among macroscopic model-MGLDM, macroscopic-RMFM and in case of semi-empirical formulae, AZF produces less deviation. Hence, these results give an insight into prediction of cluster decay half-lives in heavy and superheavy region for unknown nuclei.

Beta-decay half-lives of the isotopes close to the neutron drip line and astrophysical implications

In this paper, we examined the β −-decay half-lives of 94 extremely neutron-rich isotopes with Z = 26 − 57 close to the neutron drip line, which are important for the r-process calculations. The half-lives were calculated using four semi-empirical models and compared to those based on the FRDM+QRPA approach and available measured data. The impact of the difference in the models on the half-life predictions was investigated. We found that theoretical calculations for the β-decay half-life have a large deviation, up to 60%, which is mostly similar to that in measurements. The half-lives of the investigated nuclei are ranging from a few to hundreds of milliseconds. The r-process abundances in various astrophysical scenarios were calculated by using the predicted half-lives. The half-life uncertainty due to different models results in a large deviation in the isotopic abundance, specially for the isotopes in the mass range of A > 210. The shell closures in 76Fe is still a doubt due to the discrepancy in the trends of the half-life and paring gap while a closed-shell at N = 82 in 127Rh is possible. The results of this study also notice that it is a challenge for measuring precisely the masses of 106Rb, 116,117Nb, 122Tc, and 128Rh because of their short half-lives.

Enrichment of 150Nd for neutrinoless double-beta decay detection

A 562 nm–627 nm–597 nm three-step resonant photoionization scheme has been studied using the density matrix formalism for the enrichment of 150Nd in weighable quantities for the neutrinoless double-beta decay detection. The effect of bandwidth of the excitation laser and charge exchange collisions, on the production rates and degree of enrichment has also been studied. Optimum conditions for the efficient enrichment of 150Nd isotope have been derived. It has been shown that it might be possible to produce 50 kg of 66% enriched 150Nd isotope in about five months (16 h/day) using the conditions derived through this investigation. This enables to reach the 0νββ decay half-life limit of ≈ 1.8 × 1025 year for the 150Nd isotope.

Systematic study of alpha and cluster preformation probability using new empirical formulae

Cluster preformation probability in heavy nuclei is studied using the empirical formula of Ni and Zhou [Ren. Phys. Rev. C  82 (2010) 24311]. Dong et al. [Eur. Phys. J. A  41 (2009) 197–204], and four new formulae of Santhosh et al. [Indian J. Phys.  95 (2021) 121]. The predictions of these formulae are then compared to the preformation probabilities extracted from the experimental decay half-lives using the generalized liquid drop model (GLDM), density-dependent cluster model (DDCM), and unified fission model (UFM). It has been found that except for the isospin-dependent formula of Santhosh et al., all other formulae predict much larger preformation probability than the experimentally extracted values. Further, we propose four new empirical formulae for the cluster preformation probability in heavy nuclei, and the predictions are compared to the experimentally extracted values using different theoretical models. It is found that the predictions of all the four proposed formulae are in good agreement with the predictions of various theoretical models.

Two-neutrino double- β decay matrix elements based on a relativistic nuclear energy density functional

Nuclear matrix elements (NMEs) for two-neutrino double-beta decay ($2\nu\beta\beta$) are studied in the framework of relativistic nuclear energy density functional (REDF). The properties of nuclei involved in the decay are obtained using the relativistic Hartree-Bardeen-Cooper-Schrieffer theory and relevant nuclear transitions are described using the relativistic proton-neutron quasiparticle random phase approximation based on relativistic energy density functional (REDF-QRPA). Three effective interactions have been employed, including density-dependent meson-exchange (DD-ME2) and point coupling interactions (DD-PC1 and DD-PCX), and pairing correlations are described consistently both in $T=1$ and $T=0$ channels using a separable pairing interaction. The optimal values of $T=0$ pairing strength parameter $V_{0pp}$ are constrained by the experimental data on $\beta$-decay half lives. The $2\nu\beta\beta$ matrix elements and half-lives are calculated for several nuclides experimentally known to undergo this kind of decay: $^{48}$Ca, $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{116}$Cd, $^{124}$Xe, $^{128}$Te, $^{130}$Te, $^{136}$Xe and $^{150}$Nd. The model dependence of the NMEs and their sensitivity on $V_{0pp}$ is investigated, and the NMEs obtained using optimal values of $V_{0pp}$ are discussed in comparison to previous studies. The results of the present work represent an important benchmark for the future applications of the relativistic framework in studies of neutrinoless double-beta decay.

Deep learning approach to nuclear masses and α -decay half-lives

Ab-initio calculations of nuclear masses, the binding energy and the $\alpha$ decay half-lives are intractable for heavy nucleus, because of the curse of dimensionality in many body quantum simulations as proton number($\mathrm{N}$) and neutron number($\mathrm{Z}$) grow. We take advantage of the powerful non-linear transformation and feature representation ability of deep neural network(DNN) to predict the nuclear masses and $\alpha$ decay half-lives. For nuclear binding energy prediction problem we achieve standard deviation $\sigma=0.263$ MeV on 10-fold cross validation on 2149 nuclei. Word-vectors which are high dimensional representation of nuclei from the hidden layers of mass-regression DNN help us to calculate $\alpha$ decay half-lives. For this task, we get $\sigma=0.797$ on 100 times 10-fold cross validation on 350 nuclei on $log_{10}T_{1/2}$ and $\sigma=0.731 $ on 486 nuclei. We also find physical a priori such as shell structure, magic numbers and augmented inputs inspired by Finite Range Droplet Model are important for this small data regression task.

Abstract 2463: 18F-Talazoparib: A novel potential PET imaging agent of PARP

Abstract Background: Poly-(ADP-ribose) polymerases (PARPs) are an enzyme family that catalyze the transfer of ADP-ribose from nicotinamide adenine dinucleotide (NAD+) to an acceptor protein. PARP family members play fundamental roles in single-strand DNA break (SSB) repair, cell signaling of DNA damage and inflammation, cell death, and cellular replication. Various PARP inhibitors have been developed and PARP1 inhibitors are currently used to treat subsets of breast and ovarian cancer patients. Of all the PARP inhibitors studied, Talazoparib (Pfizer), appears to be the most stable in pre-clinical and clinical studies, affords nanomolar affinity to PARP1, and demonstrates the highest affinity trapping of PARP on the DNA-protein complex. Imaging of PARP using a radiolabeled inhibitor has been proposed for patient selection, therapy dose optimization and validation of target engagement. Several PARP imaging agents have been developed and studied as possible tracers, by modifying the structure of an original PARP inhibitor to accommodate an imaging or therapeutic isotope. Herein we used a copper-mediated 18F-radio-fluorination strategy with a novel aryl boronic ester precursor to access 18F-Talazoparib (18F-TZ), a 18F-radiolabeled form of the structurally identical Talazoparib. Methods: A novel boronic ester precursor was synthetized in six steps synthesis with an overall yield of 3.3% and characterized by NMR and mass spectrometry. Radiofluorination was performed using an automatic GE TracerLab system and analytical radioHPLC was used for tracer characterization and for stability analysis. A panel of tumor cell lines representing a variety of PARP expression levels (Hela, SUM149, SUM1315, MDA-MB-436, MDA-MB-231, PSN1, MiaPaca2, Jurkat) were tested for time-dependent uptake and specific binding, utilizing both 4 °C and excess cold TZ blocking. Results: 18F-TZ was synthetized in 5.0±0.80% (n=20) radiochemical yield and a molar activity of 18.9-98.0 GBq/µmol by a copper-mediated radiofluorination of the corresponding pinacolic boronic ester, followed by purification via semi-preparative HPLC and reformulation in ethanol. 18F-TZ was obtained in >99% radiochemical purity, displaying up to 4 hr shelf stability (25 °C and 4 °C) in PBS (10% EtOH). 18F-TZ was also stable in human plasma up to 4 hr at 37 °C. Both shelf and plasma stability tests showed a decrease of the radioHPLC peak consistent with decay half-life, but did not show the formation of secondary species. All cell lines selected for the in cellulo study showed uptake of radioactive 18F-TZ after 30 min of incubation at 37 °C. Cell uptake was blocked >98% by excess cold TZ or incubation of cells at 4 °C. Conclusion: 18F-Talazoparib was synthesized by copper-mediated radiofluorination from the corresponding pinacol ester and demonstrates both uptake and target specificity in PARP-expressing tumor cells. Citation Format: Riccardo Muzzioli, Federica Pisaneschi, Yi Rao, Seth Gammon, David Piwnica-Worms. 18F-Talazoparib: A novel potential PET imaging agent of PARP [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2463.

Improved empirical formulas for α-decay half-lives of heavy and superheavy nuclei

The empirical Royer formulas were readjusted with new set of coefficients using the latest experimental data and the recent evaluated -decay half-lives over a wide range of 573 nuclei between 52 Z 118. The effects of the orbital angular momentum, isospin asymmetry, and parity have been examined in improving the adopted formulas. The modified formulas were tested for their accuracy by comparing with the recent experimental data and other theoretical calculations. The prediction of -decay half-lives of several isotopes of the superheavy nuclei with which have not yet been experimentally synthesized, are presented and compared with other theoretical approaches. The behavior of in relation to the neutron number variation is explored for about 40 isotopes of each element. Based on the minima found in variation with neutron number, we found neutron stability at 190, 196, 200, 202, 204, 210, 216, 218, 220 and 228. The behavior of with neutron variation for heavy and superheavy nuclei is almost the same as that found using more heavy and complicated calculations. The present method can be applied easily to study large number of nuclei.

Probable chances of radioactive decays from superheavy nuclei 120290–304 within a modified generalized liquid drop model with a Q -value-dependent preformation factor

All possible chances of heavy-cluster emissions are predicted for even-even isotopes of $^{290--304}120$ using the modified generalized liquid drop model with a Q-value-dependent preformation factor. We have considered only those cluster emissions with half-life below the measurable limits. We have also estimated the probable heavy cluster emitted from each isotope of $^{290--304}120$ with half-life comparable to $\ensuremath{\alpha}$-decay half-life and the most probable cluster emission with the least half-life among all cluster-daughter combinations possible, and the predicted decays have either magic number of protons or neutrons or near to it. The highest and second highest $\ensuremath{\alpha}$-decay half-life from $^{290--304}120$ corresponds to $^{298}120$ and $^{304}120$, both isotopes with magic or semimagic numbers. Thus, the role of the magic number in stability is highlighted through our paper. The predicted $\ensuremath{\alpha}$ half-lives are compared with other theoretical models and are in agreement. For the first time we explore the possibility of $2\ensuremath{\alpha}$ decay from the superheavy (SH) nuclei. The agreement in theoretical $\ensuremath{\alpha}$-decay half-lives with experimental values for the isotopes in the decay chains of $Z=120$ shows the predictability of the model in the SH region, and so we predict the isotopes $^{290,292}120$ decays by $6\ensuremath{\alpha}$-decay chains and even-even isotopes $^{294--304}120$ decays by $4\ensuremath{\alpha}$-decay chains. Our predictions become particularly important as the predicted half-lives are within experimentally measurable limits and can be detected in the near future.

New behaviors of α-particle preformation factors near doubly magic 100Sn * *Supported by the National Natural Science Foundation of China (12175170, 11675066, 12005303)

The -particle preformation factors of nuclei above doubly magic nuclei Sn and Pb are investigated within the generalized liquid drop model. The results show that the -particle preformation factors of nuclei near self-conjugate doubly magic Sn are significantly larger than those of analogous nuclei just above Pb, and they will be enhanced as the nuclei move towards the line. The proton–neutron correlation energy and two protons–two neutrons correlation energy of nuclei near Sn also exhibit a similar situation, indicating that the interactions between protons and neutrons occupying similar single-particle orbitals could enhance the -particle preformation factors and result in superallowed decay. This also provides evidence of the significant role of the proton–neutron interaction on -particle preformation. Also, the linear relationship between -particle preformation factors and the product of valence protons and valence neutrons for nuclei around Pb is broken in the Sn region because the -particle preformation factor is enhanced when a nucleus near Sn moves towards the line. Furthermore, the calculated decay half-lives fit well with the experimental data, including the recent observed self-conjugate nuclei Te and Xe [Phys. Rev. Lett. 121, 182501 (2018)].