Tue·May 2, 2023Tuesday·May 2, 2023

1. 01*

   A walk along the proton drip-line by $\beta$-decay spectroscopy

   S.E.A. Orrigo🇪🇸 · B. Rubio🇪🇸 · W. Gelletly🇬🇧

   During the last decade we have carried out a systematic study of the $\beta$ decay of neutron-deficient nuclei, providing rich spectroscopic information of importance for both nuclear structure and nuclear astrophysics. We present an overview of the most relevant achievements, including the discovery of a new exotic decay mode in the fp-shell, the $\beta$-delayed $\gamma$-proton decay in ${}^{56}$Zn, the first observation of the 2${}^{+}$ isomer in ${}^{52}$Co and the latest results on the heavier systems ${}^{60}$Ge and ${}^{62}$Ge. We also report on our deduced mass excesses in comparison with systematics and a recent measurement. Finally, we summarise our results on the half-lives of $T_z=$ -1/2, -1 and -2 neutron-deficient nuclides, and analyse their trend.

   nucl-exEPJ Web Conf.(2023)·4 citations
2. 02*

   Hypernuclear event detection in the nuclear emulsion with Monte Carlo simulation and machine learning

   A. Kasagi🇯🇵 · W. Dou🇯🇵 · V. Drozd🇯🇵 · H. Ekawa🇯🇵 · S. Escrig🇯🇵 · Y. Gao🇯🇵 · Y. He🇯🇵 · E. Liu🇯🇵 · A. Muneem🇯🇵 · M. Nakagawa🇯🇵 · K. Nakazawa🇯🇵 · C. Rappold🇪🇸 and 9 other authors

   This study developed a novel method for detecting hypernuclear events recorded in nuclear emulsion sheets using machine learning techniques. The artificial neural network-based object detection model was trained on surrogate images created through Monte Carlo simulations and image-style transformations using generative adversarial networks. The performance of the proposed model was evaluated using $\alpha$-decay events obtained from the J-PARC E07 emulsion data. The model achieved approximately twice the detection efficiency of conventional image processing and reduced the time spent on manual visual inspection by approximately 1/17. The established method was successfully applied to the detection of hypernuclear events. This approach is a state-of-the-art tool for discovering rare events recorded in nuclear emulsion sheets without any real data for training.

   nucl-exphysics.ins-detNucl.Instrum.Meth.A(2023)·6 citations
3. 03*

   Searching for ${}^{76}$Ge neutrinoless double beta decay with the CDEX-1B experiment

   B. T. Zhang · J. Z. Wang · L. T. Yang🇨🇳 · Q. Yue · K. J. Kang🇨🇳 · Y. J. Li · H. P. An🇨🇳 · Greeshma C.🇹🇼 · J. P. Chang🇨🇳 · Y. H. Chen🇨🇳 · J. P. Cheng🇨🇳 · W. H. Dai🇨🇳 and 73 other authors

   We operated a p-type point contact high purity germanium (PPCGe) detector (CDEX-1B, 1.008 kg) in the China Jinping Underground Laboratory (CJPL) for 500.3 days to search for neutrinoless double beta ($0\nu \beta \beta$) decay of ${}^{76}$Ge. A total of 504.3 kg$\cdot$day effective exposure data was accumulated. The anti-coincidence and the multi/single-site event (MSE/SSE) discrimination methods were used to suppress the background in the energy region of interest (ROI, 1989$-$2089 keV for this work) with a factor of 23. A background level of 0.33 counts/(keV$\cdot$kg$\cdot$yr) was realized. The lower limit on the half life of ${}^{76}$Ge $0\nu \beta \beta$ decay was constrained as $T_{1/2}^{0\nu }>1.0\times 10^{23}\mathrm{yr}(90\%C.L.)$, corresponding to the upper limits on the effective Majorana neutrino mass: $⟨m_{\beta \beta }⟩<$3.2$-$7.5$\mathrm{eV}$.

   nucl-exhep-exphysics.ins-detCPC(2024)·16 citations
4. 04*

   Bayesian Inference of Supernova Neutrino Spectra with Multiple Detectors

   Xu-Run Huang🇨🇳 · Chuan-Le Sun🇨🇳 · Lie-Wen Chen🇨🇳 · Jun Gao🇨🇳

   We implement the Bayesian inference to retrieve energy spectra of all neutrinos from a galactic core-collapse supernova (CCSN). To achieve high statistics and full sensitivity to all flavours of neutrinos, we adopt a combination of several reaction channels from different large-scale neutrino observatories, namely inverse beta decay on proton and elastic scattering on electron from Hyper-Kamiokande (Hyper-K), charged current absorption on Argon from Deep Underground Neutrino Experiment (DUNE) and coherent elastic scattering on Lead from RES-NOVA. Assuming no neutrino oscillation or specific oscillation models, we obtain mock data for each channel through Poisson processes with the predictions, for a typical source distance of 10 kpc in our Galaxy, and then evaluate the probability distributions for all spectral parameters of theoretical neutrino spectrum model with Bayes' theorem. Although the results for either the electron-neutrinos or electron-antineutrinos reserve relatively large uncertainties (according to the neutrino mass hierarchy), a precision of a few percent (i.e., $\pm 1\%\sim \pm 4\%$ at a credible interval of $2\sigma$) is achieved for primary spectral parameters (e.g., mean energy and total emitted energy) of other neutrino species. Moreover, the correlation coefficients between different parameters are computed as well and interesting patterns are found. Especially, the mixing-induced correlations are sensitive to the neutrino mass hierarchy, which potentially makes it a brand new probe to determine the neutrino mass hierarchy in the detection of galactic supernova neutrinos. Finally, we discuss the origin of such correlation patterns and perspectives for further improvement on our results.

   ↳ hep-phastro-ph.HEnucl-exnucl-thJCAP(2023)·10 citations
5. 05*

   DT fusion through the ${}^5$He $3/2+$ "Bretscher state" accounts for $\ge 25\%$ of our existence via nucleosynthesis and for the possibility of fusion energy

   Mark B. Chadwick · Mark W. Paris🇺🇸 · Brian M. Haines

   In big bang nucleosynthesis (BBN), the deuterium-tritium (DT) fusion reaction, D(T,n)$\alpha$, enhanced by the 3/2${}^{+}$ resonance, is responsible for 99% of primordial ${}^4$He. This has been known for decades and has been well documented in the scientific literature. However, following the tradition adopted by authors of learned articles, it was stated in a matter-of-fact manner and not emphasized; for most people, it has remained unknown. This helium became a source for the subsequent creation of $\ge$25% of the carbon and other heavier elements and, thus, a substantial fraction of our human bodies. (To be more precise than $\ge$25% will require future simulation studies on stellar nucleosynthesis.) Also, without this resonance, controlled fusion energy would be beyond reach. For example, for inertial confinement fusion (ICF), laser energy delivery for the National Ignition Facility (NIF) would have to be approximately 70 times larger for ignition. Because the resonance enhances the DT fusion cross section a hundredfold, we propose that the 3/2${}^{+}$ ${}^5$He excited state be referred to as the "Bretscher state" in honor of the Manhattan Project scientist who discovered it, in analogy with the well-known 7.6 MeV "Hoyle state" in ${}^{12}$C that allows for the resonant 3$\alpha$ formation.

   ↳ physics.hist-phastro-ph.SRnucl-exnucl-th4 citations
6. 06*

   Impact of isovector pairing fluctuation on neutrinoless double-beta decay in multi-reference covariant density functional theory

   C. R. Ding🇨🇳 · X. Zhang🇨🇳 · J. M. Yao🇨🇳 · P. Ring🇩🇪 · J. Meng🇨🇳

   We extend the multi-reference covariant density functional theory (MR-CDFT) by including fluctuations in quadrupole deformations and average isovector pairing gaps simultaneously for the nuclear matrix elements (NMEs) of neutrinoless double-beta $(0\nu \beta \beta )$ decay in the candidate nuclei ${}^{76}$Ge, ${}^{82}$Se, ${}^{100}$Mo, ${}^{130}$Te, and ${}^{136}$Xe assuming the exchange of either light or heavy neutrinos. The results indicate a linear correlation between the predicted NMEs and the isovector pairing strengths, as well as the excitation energies of $2_1^{+}$ and $4_1^{+}$ states. By adjusting the pairing strengths based on the excitation energies of the $2_1^{+}$ states, we calculate the NMEs for $0\nu \beta \beta$ decay, which are reduced by approximately $12\%$ to $62\%$ compared to the results obtained in the previous studies by Song et al. [Phys. Rev. C95, 024305 (2017)]. Additionally, upon introducing the average isovector pairing gap as an additional generator coordinate in the calculation, the NMEs increase by a factor ranging from $56\%$ to $218\%$.

   ↳ nucl-thhep-phnucl-exPRC(2023)·11 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.