Tue·Mar 4, 2025Tuesday·March 4, 2025

1. 01*

   $Z=14$ Magicity Revealed by the Mass of the Proton Dripline Nucleus ${}^{22}$Si

   Y. M. Xing · Y. F. Luo🇨🇳 · Y. H. Zhang🇩🇪 · M. Wang🇨🇳 · X. H. Zhou🇨🇳 · J. G. Li🇨🇳 · K. H. Li · Q. Yuan🇨🇳 · Y. F. Niu🇨🇳 · J. Y. Guo🇩🇪 · J. C. Pei🇨🇳 · F. R. Xu🇨🇳 and 27 other authors

   Using the $B\rho$-defined isochronous mass spectrometry technique, we conducted the first mass measurement of the proton dripline nucleus ${}^{22}$Si. We confirm that ${}^{22}$Si is bound against particle emission with $S_p/S_{2p}=+1412(114)/+229(54)$ keV, fixing the proton dripline location for the Si element. By analyzing the mass differences of the neighboring $sd$-shell nuclei, we find that ${}^{22}$Si exhibits a doubly-magic character similar to its mirror partner ${}^{22}$O, and that the mirror energy difference of ${}^{22}$Si-${}^{22}$O deviates from the predictions assuming mirror symmetry. Gamow shell-model calculations reveal that the average occupations of valence protons in ${}^{22}$Si are nearly identical to those of valence neutrons in ${}^{22}$O, supporting the $Z=14$ magicity in ${}^{22}$Si. The observed mirror-symmetry breaking is attributed to the extended proton distribution in ${}^{22}$Si arising from a small contribution of the unbound $\pi 2s_{1/2}$ orbital.

   nucl-exnucl-thPRL(2025)·20 citations
2. 02*

   Improved sensitivity in the search for rare decays of Gd isotopes

   B. Lehnert🇩🇪 · S. S. Nagorny🇮🇹 · M. Thiesse🇬🇧 · F. Ferella🇮🇹 · M. Laubenstein🇮🇹 · E. Meehan🇲🇽 · S. Nisi🇮🇹 · P. R. Scovell🇲🇽

   Gadolinium is widely used in multiple low-background experiments, making its isotopes accessible for rare decay searches both in-situ and through radiopurity screening data. This study presents an improved search for rare alpha and double-beta decay modes in ${}^{152}$Gd, ${}^{154}$Gd, and ${}^{160}$Gd isotopes using ultra-low background HPGe detectors at the Boulby Underground Screening (BUGS) facility. A total exposure of 6.7 kg$\cdot$yr of natural gadolinium was achieved using gadolinium sulfate octahydrate $({\text{Gd}}_2({\text{SO}}_4{)}_3\cdot 8{\text{H}}_2\text{O})$ samples, originally screened for radiopurity prior to their deployment in the Super-Kamiokande neutrino experiment. Due to the detection methodology, only decays into excited states accompanied by gamma-ray emission were accessible. A Bayesian analysis incorporating prior experimental results was employed, leading to new lower half-life limits in the range of $10^{19}-10^{21}$ years - an improvement of approximately two orders of magnitude over previous constraints. No statistically significant decay signals were observed. These results demonstrate the effectiveness of repurposing large-scale radiopurity screening campaigns for fundamental physics research.

   nucl-exhep-exEPJC(2025)·1 citation
3. 03*

   Towards AMS measurements of ${}^{91}$Nb, ${}^{94}$Nb and ${}^{93}$Mo produced in fusion environment

   Carlos Vivo-Vilches · Esad Hrnjic · Martin Martschini · Kyra Altindag · Lee William Packer🇬🇧 · Robin Golser · Karin Hain

   Long-lived radionuclides, such as ${}^{91}$Nb, ${}^{94}$Nb and ${}^{93}$Mo, are expected to be produced in nuclear fusion reactors by reactions of high-energy neutrons with the structural material. Accurate predictions of waste categorization require experimental validation of simulation codes like FISPACT-II. This work explores the use of Ion-Laser InterAction Mass Spectrometry (ILIAMS) at the Vienna Environmental Research Accelerator (VERA) to measure these three radionuclides by accelerator mass spectrometry (AMS). The ILIAMS setup employs laser photodetachment to suppress their respective stable isobars: ${}^{91}$Zr, ${}^{94}$Zr and ${}^{94}$Mo, and ${}^{93}$Nb. For ${}^{91,94}$Nb measurements, NbO${}_3^{-}$ is selected, with interferences from ZrO${}_3^{-}$ suppressed by collisions with the He buffer gas in the ion cooler. The suppression can be enhanced by overlapping a 355\,nm laser with the ion beam. The lower limit for the suppression factor is 37000. In that way, we reach ${}^{91}$Zr/${}^{93}$Nb and ${}^{94}$Zr/${}^{93}$Nb levels of $1.2\times 10^{-14}$ and $1.8\times 10^{-14}$, respectively, in targets prepared from commercial Nb${}_2$O${}_5$. MoO${}_3$ is suppressed by a factor of 4360, leading to a ${}^{94}$Mo/${}^{93}$Nb interference of $1.28\times 10^{-10}$ in the same targets. For ${}^{93}$Mo measurements, MoO${}_2^{-}$ is selected, with interference from ${}^{93}$NbO${}_2^{-}$ suppressed by 637\,nm photons by a factor of $5.5\times 10^6$. This results in a ${}^{93}$Nb/${}^{\text{nat}}$Mo level of $1.3\times 10^{-13}$ in targets prepared from commercial MoO${}_3$. Suppression factors as high as this are not achieved by isobar suppression techniques based on differences in energy loss, not even by AMS facilities with terminal voltages above 8.5\,MV.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2025)·0 citations
4. 04*

   Effective proton-neutron interaction in mirror nuclei

   Y. M. Xing · Y. F. Luo🇨🇳 · K. H. Li · Y. H. Zhang🇨🇳 · J. G. Li🇨🇳 · M. Wang🇨🇳 · Yu. A. Litvinov🇩🇪 · K. Blaum🇩🇪 · X. L. Yan🇨🇳 · T. Liao · M. Zhang🇺🇸 · X. Zhou

   Effective proton-neutron interactions, $V_{pn}$, in mirror nuclei are systematically analyzed using the ground-state atomic masses. A mirror symmetry of $V_{pn}$ is found for bound nuclei with a standard deviation of $\sigma =32$ keV. However, this mirror symmetry is apparently broken for some mirror-nuclei pairs when a proton-unbound nucleus is involved in extracting the $V_{pn}$ values. Such a mirror-symmetry breaking is attributed to the Thomas-Ehrman shift of the proton-unbound nucleus and investigated by using the Gamow shell model. It is concluded that the Thomas-Ehrman shift originates mainly from reduced Coulomb energies in the proton-unbound nuclei due to the extended radial density distribution of valence protons.

   ↳ nucl-thnucl-exPRC(2025)·4 citations
5. 05*

   Charmed hadron production from secondary anti-proton + proton annihilations in p+A reactions at FAIR

   Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪

   We present estimates for the production cross sections of exotic states (${\Lambda }_c,{\Sigma }_c,{\Xi }_c,D\mathrm{and}{D}_s$) from secondary $\overline{B}+B$ annihilations in p+A reactions from $E_{\mathrm{lab}}=10-30A$~GeV. We focus specifically on the newly planned hadron physics program of CBM at FAIR. These estimates for the production of exotic states are based on the achievable number of $\overline{B}+B$ annihilations and their invariant mass distributions calculated in the UrQMD transport model.

   ↳ nucl-thhep-phnucl-exEPJA(2025)·5 citations
6. 06*

   CUPID, the CUORE Upgrade with Particle IDentification

   The CUPID Collaboration: K. Alfonso🇺🇸 · A. Armatol🇺🇸 · C. Augier🇫🇷 · F. T. Avignone III🇺🇸 · O. Azzolini🇮🇹 · A.S. Barabash🇷🇺 · G. Bari🇮🇹 · A. Barresi🇮🇹 · D. Baudin🇫🇷 · F. Bellini🇮🇹 · G. Benato🇮🇹 · L. Benussi🇮🇹 and 180 other authors

   CUPID, the CUORE Upgrade with Particle IDentification, is a next-generation experiment to search for neutrinoless double beta decay ($0\nu \beta \beta$) and other rare events using enriched Li${}_2$${}^{100}$MoO${}_4$ scintillating bolometers. It will be hosted by the CUORE cryostat located at the Laboratori Nazionali del Gran Sasso in Italy. The main physics goal of CUPID is to search for $0\nu \beta \beta$\ of ${}^{100}$Mo with a discovery sensitivity covering the full neutrino mass regime in the inverted ordering scenario, as well as the portion of the normal ordering regime with lightest neutrino mass larger than 10 meV. With a conservative background index of 10${}^{-4}$ cnts/(keV$\cdot$kg$\cdot$yr), 240 kg isotope mass, 5 keV FWHM energy resolution at 3 MeV and 10 live-years of data taking, CUPID will have a 90\% C.L. half-life exclusion sensitivity of 1.8 $\cdot$ 10${}^{27}$ yr, corresponding to an effective Majorana neutrino mass ($m_{\beta \beta }$) sensitivity of 9--15 meV, and a $3\sigma$ discovery sensitivity of 1 $\cdot$ 10${}^{27}$ yr, corresponding to an $m_{\beta \beta }$ range of 12--21 meV.

   ↳ physics.ins-dethep-exnucl-exEPJC(2025)·33 citations
7. 07*

   Development and Benchmarking of JANGOFETT: A Novel Geant4-Operated Fission Event Tracking Tool

   Liam Walker · Jack Shire · Jacob Jaffe · Payton Sprando · Jack Olinger · Alexander Chemey🇺🇸

   Experiments measuring fission observables encounter false coincidences arising from timing overlap of separate fission product decays. Simulations of both fission observables and particles in detector systems exist, but have not yet been combined to produce accurate event-by-event outputs in a time-dependent manner. Geant4 is a powerful simulation tool for nuclear physics studies, but it does not handle multiple initial particles in a single simulation instance, nor does it feature high fidelity fission sampling. JANGOFETT: A Novel Geant4-Operated Fission Event Tracking Tool has been developed to address this challenge. The tool utilizes simulated fission data from an external program in conjunction with Geant4, which has been modified to produce a single timeline of events over an entire simulated experiment. The physical accuracy of the simulated overlapping energy depositions within detectors has been verified via simulation of fission products from the spontaneous fission of 252Cf.

   ↳ physics.ins-detnucl-exnucl-thNucl.Instrum.Meth.A(2026)·0 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.