Nuclear Experiment·nucl-ex

Tue·Jul 14, 2026Tuesday·July 14, 2026

13 papers—7 primary·6 cross-listed

01
High-Precision Mass Measurements of 52Ni and 51Co Reveal Breakdown of the Isobaric Multiplet Mass Equation in the f p Shell
F. M. Maier🇺🇸 · G. Bollen🇺🇸 · B. A. Brown🇺🇸 · S. E. Campbell🇺🇸 · X. Chen🇨🇳 · H. Erington🇺🇸 · N. D. Gamage🇺🇸 · K. Godbey🇺🇸 · C. M. Ireland🇺🇸 · C. Izzo🇺🇸 · R. Ringle🇺🇸 · C. S. Sumithrarachchi🇺🇸 · A. C. C. Villari
We performed high-precision mass measurements of the proton-rich nuclei $^{52}$ Ni and $^{51}$ Co with the LEBIT Penning trap at the Facility for Rare Isotope Beams (FRIB). For $^{52}$ Ni, a mass excess of $- 22474.8 (2.2)$ ~keV was determined, which is consistent with a recent storage-ring measurement at the Cooler-Storage Ring (CSRe) but has a factor 37 improved precision. For $^{51}$ Co, we obtained a mass excess of $- 27375.1 (5.7)$ ~keV, agreeing with a recent CSRe result, while reducing the uncertainty by a factor~2. Combining our mass value for $^{52}$ Ni with the known two-proton decay energy of $^{54}$ Zn, we determined the mass excess of $^{54}$ Zn to be $- 6463 (42)$ ~keV. These new mass values reveal a substantial breakdown of the isobaric mass multiplet equation for $A = 52$ and $A = 54$ , and provide stringent benchmarks for isospin-symmetry-breaking effects in the proton-rich $f p$ -shell, favoring theoretical descriptions that omit the Coulomb-exchange term.
nucl-ex0 citations
02
Precision masses of neutron-rich platinum and gold nuclei reveal enhanced $N = 126$ shell strength below doubly-magic $^{208}$ Pb
David Freire-Fernández🇩🇪 · Rui-Jiu Chen🇩🇪 · Usama Ahmed🇩🇪 · Helena M. Albers🇩🇪 · Jelena Bardak🇩🇪 · Carsten Brandau🇩🇪 · Jeroen P. Bormans🇩🇪 · R. Burcu Cakirli🇩🇪 · Rikel Chakma🇺🇸 · Maeve Cockshutt🇨🇦 · Iris Dillmann🇨🇦 · Dmytro Dmytriiev🇩🇪 and 54 other authors
The heaviest stable nuclei in the universe owe their existence to quantum shell structure, the grouping of protons and neutrons into discrete energy levels separated by gaps. The largest known neutron shell gap in stable nuclei, at $N = 126$ , stabilizes doubly-magic $^{208}$ Pb and is responsible for the characteristic abundance peak of heavy elements near gold and platinum produced by the rapid neutron-capture process (r-process). Whether this shell gap persists as protons are removed from lead is a question central to both nuclear structure and the modeling of heavy-element synthesis, yet it has remained unanswered due to the extraordinary difficulty of producing the relevant neutron-rich nuclei. Direct experimental knowledge in this region was essentially absent. Here we report the first precision mass measurements of $^{203, 204}$ Pt and $^{204, 205, 206}$ Au, performed at GSI using a novel combination of Schottky and isochronous mass spectrometry in a heavy-ion storage ring. The $N = 126$ isotones $^{204}$ Pt and $^{205}$ Au are more strongly bound than the extrapolated trend of the previously known mass surface by 403 and 464~keV, respectively, revealing an unexpectedly enhanced $N = 126$ shell strength below doubly-magic $^{208}$ Pb. Furthermore, the proton-neutron interaction strength exhibits a hitherto unobserved bifurcation at $N = 126$ as protons are removed from $^{208}$ Pb. Our results redefine the nuclear mass surface in the neutron-rich heavy-element region and provide direct experimental benchmarks for theoretical models whose extrapolations toward more exotic nuclei are essential for r-process nucleosynthesis calculations.
nucl-exnucl-th0 citations
03
Exploring the origin of D $^{0}$ meson elliptic flow in PbPb collisions at $s_{NN}$ = 5.02 TeV using event shape engineering
CMS Collaboration
The influence of the initial-state geometry on the elliptic flow of prompt D $^{0}$ mesons in high-energy heavy ion collisions is explored. A lead-lead (PbPb) data sample at a center-of-mass energy per nucleon pair of 5.02 TeV and with an integrated luminosity of 0.607 nb $^{- 1}$ was collected in 2018 with the CMS detector at the CERN LHC. Based on these data, an event-shape engineering technique is used to isolate collisions with similar geometrical properties. An asymmetry parameter, $q_{2}$ , is first determined from the distribution of transverse energy in the forward region of the detector. This parameter is shown to be linearly correlated with the elliptic anisotropy of inclusive charged particles measured near mid-rapidity, as characterized by the second-order Fourier coefficients, $v_{2}$ . Taking the charged particle $v_{2}$ coefficients as proxies for the initial-state eccentricity, the correlation of D $^{0}$ meson $v_{2}$ values near mid-rapidity with those of inclusive charged particles is then studied. For D $^{0}$ mesons with transverse momenta in the range of 2 $-$ 30 GeV and for different degrees of collision overlap, the $v_{2}$ values are found strongly correlated with those for charged particles when selected based on similar $q_{2}$ intervals. This correlation suggests that the initial-state geometry substantially impacts the development of charm-hadron flow in heavy ion collisions. A model calculation that explores the thermalization and collective motion of D $^{0}$ mesons and charged particles is compared to the experimental results.
nucl-exhep-ex0 citations
04
Observation of the centrality-dependent difference in directed flow between charged kaons and $K^{* 0}$ resonances in Au+Au collisions at $s_{NN}$ = 14.6, 19.6 and 27 GeV
STAR Collaboration
We present the measurement of rapidity-odd directed flow ( $v_{1}^{odd}$ ) for charged kaons, $ϕ$ mesons, and $K^{* 0} (K^{* 0})$ resonances in Au+Au collisions at $s_{NN}$ = 14.6, 19.6 and 27 GeV. This study includes the first measurement of the $K^{* 0}$ resonance $v_{1}^{odd}$ in heavy-ion collisions. Our measurement shows a centrality-dependent difference in directed flow between charged kaons and $K^{* 0}$ resonances, which becomes more pronounced with increasing collision centrality. In contrast, the difference in directed flow between charged kaons and $ϕ$ mesons remains nearly independent of centrality. Although anisotropic flow is thought to be developed in the early stages of the collision, for short-lived resonances such as the $K^{*} (892)$ that experience substantial hadronic re-scattering, it remains unclear to what extent the observed $v_{1}^{odd}$ reflects genuine partonic collectivity in the early stage, and to what extent it is altered by late-stage hadronic interactions and/or reconstruction effects. The present measurement is crucial for disentangling these contributions and addressing this question. Existing hydrodynamic calculations that include a hadronic afterburner based on the UrQMD model indicate that an asymmetric modification of the $K^{* 0}$ yield, due to rescattering, relative to the first-order event plane is required to reproduce the observed difference between $v_{1}^{odd}$ for charged kaons and $K^{* 0}$ .
nucl-ex0 citations
05
Structure of even-even Zr isotopes with 52 $\leq$ N $\leq$ 58 neutrons
W. Urban🇵🇱 · A. Abramuk🇵🇱 · T. Rzcaca-Urban🇵🇱 · M. Jentschel🇫🇷 · P. Mutti🇫🇷 · U. Köster🇫🇷 · G. de France🇫🇷 · C.A. Ur🇮🇹
Excited levels in $^{92}$ Zr have been studied in cold-neutron capture reaction using the EXILL Ge array at ILL Grenoble. Excited levels in $^{94}$ Zr and $^{98}$ Zr nuclei have been studied using high-statistics $γ$ -coincidence data from neutron-induced fission of $^{235}$ U measured with EXILL. The goal of was to search for new levels in $^{92, 94, 98}$ Zr and to improve spin-parity assignments to excited levels. Total of 54 new levels, 180 new $γ$ transitions and 70 new or improved spin-parity assignments have been determined in the three isotopes in the present work. A precise neutron binding energy of 8634.81(2) keV has been determined in $^{92}$ Zr. In $^{94}$ Zr a Gamow-Teller transition is proposed. The (9 $^{-}$ ), 3894.1-keV level in $^{98}$ Zr is likely a few ns isomer. A new technique of estimating half-lives in a picosecond range, developed in this work, provided 61 half-lives and 60 B( $π, λ$ ) rates for transitions in $^{96, 98}$ Zr and $^{94, 96}$ Sr. New-type systematics, backed by Large Scale Shell Model calculations have been used to classify 2 $^{+}$ excitations in Zn-Zr even-even nuclei of the 50 $\leq$ N $\leq$ 60 range. This information and new systematics of 0 $^{+}$ excitations in Sr and Zr isotopes explain the evolution of collectivity in zirconium isotopes, showing the role of various single particle excitations in the phase transition and coexistence of the region. The role of the $ν$ 9/2 $^{+}$ [404] extruder orbital as a catalyst in creating 0 $^{+}$ excitations and the deformation change in the region has been discussed.
nucl-ex0 citations
06
Search for two-neutrino double electron capture in $^{36}$ Ar with the DarkSide-50 detector
DarkSide-50 Collaboration · P. Agnes · I.F.M. Albuquerque · T. Alexander · A.K. Alton · M. Ave Pernas · H.O. Back · G. Batignani · W.M. Bonivento · B. Bottino · S. Bussino · M. Cadeddu and 74 other authors
Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shells and two neutrinos are emitted. We report on the first search for two-neutrino double electron capture in the $KK$ - and $KL$ -shells of $^{36}$ Ar using the low-radioactivity liquid argon target from underground sources in the DarkSide-50 experiment. No statistically significant excess was observed with approximately 12 ton-day exposure of underground argon (UAr) and, taking into account the $^{36}$ Ar isotopic abundance in UAr (0.007%), we set a limit on the half-life of the two-electron capture process in $^{36}$ Ar of $T_{1/2} > 9.2 \times 1 0^{19}$ yr at 90% C.L. The sensitivity of the DarkSide-20k experiment, which will become operational in the next few years, was also evaluated and is expected to increase by a factor $\sim$ 100 with 10 years of expected operation and assuming the same $^{36}$ Ar abundance as in the DarkSide-50 underground argon target.
nucl-exhep-ex0 citations
07
Experimental Review on Bulk Properties and Light/Strange Hadron Production in Heavy-Ion Collisions
Shusu Shi🇨🇳 · Xianglei Zhu🇨🇳
This proceedings article reviews recent experimental results on bulk properties and light/strange hadron production in heavy-ion collisions, presented at the Strangeness in Quark Matter 2026 conference. The discussion covers the QCD phase diagram, extraction of the temperature-dependent speed of sound, radial flow fluctuations probed by $v_{0} (p_{T})$ , anisotropic flow in small collision systems, strange hadron yields across system sizes, nuclear modification factors, and collectivity signatures at high baryon density. Results from the STAR, CMS, ALICE, ATLAS, PHENIX, NA61/SHINE, and HADES collaborations are synthesized to highlight recent progress in understanding the properties of the Quark-Gluon Plasma and the nature of the QCD phase transition.
nucl-ex0 citations
08
Absence of a shell closure in $^{140}$ Sn
Francesca Bonaiti🇺🇸 · Bingcheng He🇺🇸 · Gaute Hagen🇺🇸 · Thomas Papenbrock🇺🇸
There are conflicting theoretical results about the presence of a shell closure in the neutron-rich nucleus $^{140}$ Sn. We address this controversy by performing ab initio computations, using a nuclear interaction from chiral effective field theory that accurately reproduced and predicted low-lying states in doubly magic nuclei. We verify that this interaction accurately reproduces low-lying states in $^{133}$ Sn. We assume that $^{140}$ Sn exhibits a closed $7/ 2^{-}$ neutron subshell beyond $^{132}$ Sn and compute its first excited $2^{+}$ state. The resulting energy is small and this contradicts the assumption.
↳ nucl-thnucl-ex1 citation
09
A Lawson-inspired Cycle-Closure Criterion for Deuterium--Tritium Muon-Catalyzed Fusion
Wei Kou🇨🇳 · Xurong Chen🇨🇳
Deuterium--tritium muon-catalyzed fusion is limited by a cycle-closure problem: a negative muon must complete enough catalytic cycles before decay or effective alpha sticking removes it from reuse. We formulate a Lawson-inspired criterion for this single-muon cycle. The effective cycle strength is defined as $L_{μ} = Λ_{c} τ_{μ}$ , where $Λ_{c}$ is the effective cycle-completion rate and $τ_{μ}$ is the muon lifetime. Together with the residual effective sticking probability $ω_{S}^{eff}$ , it gives the mean fusion yield per useful muon, $N_{fus, μ} = L_{μ} / (1 + ω_{S}^{eff} L_{μ})$ . Introducing the useful D--T cycle energy $E_{use}$ , the system factor $η_{sys}$ , and the effective muon cost $E_{μ}^{cost}$ , the one-muon gain is $G_{μ} = (η_{sys} E_{use} / E_{μ}^{cost}) N_{fus, μ}$ . This leads to the required cycle strength $L_{μ}^{req} = G_{μ} N_{L} / (1 - ω_{S}^{eff} G_{μ} N_{L})$ , with $N_{L} = E_{μ}^{cost} / (η_{sys} E_{use})$ , and to the conditional sticking boundary $ω_{S}^{eff} < 1/ (G_{μ} N_{L})$ . The criterion separates rate-limited, sticking-limited, and cost-limited regimes in the $(ω_{S}^{eff}, L_{μ})$ plane. When representative historical D--T $μ CF$ anchors are projected onto this plane, they lie in a high-yield region but remain constrained by the effective-sticking boundary under conventional multi-GeV muon-cost accounting. The framework provides a compact diagnostic for assessing whether future improvements act mainly by increasing the effective cycle-completion rate, reducing residual sticking, or lowering the useful cost of delivered muons.
↳ nucl-thnucl-ex0 citations
10
Determination of the Odderon amplitude in elastic cross-sections at high energies from scaling and analyticity
J. A. velazquez Corral🇺🇸 · B. G. Giraud🇫🇷 · R. Peschanski🇫🇷 · C. Royon🇺🇸
Scaling amplitudes describing $pp$ elastic scattering differential cross-sections in the dip-bump region of momentum transfer at the LHC have been recently derived~\cite{scaling}. We check that the same scaling is verified by the $p p ˉ$ cross-section at the highest energy of the Tevatron. Applying the general "energy to phase" relation for a given signature, coming from the analiticity properties inherent to the S-Matrix formalism~\cite{chew}, we derive the scaling amplitude with positive signature (i.e. the Pomeron). Fitting the $pp$ differential cross-sections measured by the TOTEM collaboration leads to some tension with data in the experimental dip observed at moderate momentum transfer. Concentrating the study to the dip/bump region, we are able to determine a contribution of a negative signature amplitude (i.e. the Odderon) leading to a parameter free prediction for the $p p ˉ$ differential cross-section which is in agreement with the D0 data. The extraction of the Odderon amplitude in both modulus and phase is then performed and discussed.
↳ hep-phhep-exnucl-exnucl-th2 citations
11
Ab initio study of $β$ -decay and pairing in $N = Z$ nuclei
Subhrajit Sahoo🇮🇳 · Praveen C. Srivastava🇮🇳
We investigate the $β$ -decay properties of $r p$ -process waiting-point nuclei $^{72}$ Kr, $^{68}$ Se, and $^{64}$ Ge from realistic nuclear forces based on chiral effective field theory. The \textit{ab initio} valence-space in-medium similarity renormalization group method is employed for this purpose to consistently derive Hamiltonians and Gamow-Teller operators from chiral two- and three-nucleon interactions. The calculated half-lives and branching ratios indicate that nearly the entire decay intensity is confined within 1 MeV of excitation energy in the daughter nuclei. We address the isoscalar and isovector pairing and their impact on ground state properties of these waiting-point nuclei, along with several other $N = Z$ systems in the $f p$ -shell. Our results do not provide evidence for an isoscalar condensate or any dominant isovector pairing condensate-like phase in these $N = Z$ nuclei. We present the full $B (GT)$ strength distributions and discuss the influence of pairing correlations on them. The present work provides a microscopic picture of $β$ -decay strengths and pairing in $N = Z$ nuclei far from the stability line.
↳ nucl-thnucl-exPRC(2026)·1 citation
12
Machine Learning-Based Reconstruction for Resistive Silicon Sensors
Alexander Aoki🇺🇸 · Gaetano Barone🇺🇸 · Leena Diehl🇨🇭 · Gabriele Giacomini🇺🇸 · Vagelis Gkougkousis🇨🇭 · Hanshal Goyal🇺🇸 · Rohan Kher🇺🇸 · Daniel Li🇺🇸 · Anna Macchiolo🇨🇭 · Yevhenii Padnuik🇨🇭 · Daria Senina🇨🇭 · Samantha Sunnarborg🇺🇸 and 4 other authors
Low-Gain Avalanche Diodes (LGADs) and AC-coupled Low-Gain Avalanche Diodes (AC-LGADs) are promising technologies for precision timing and four-dimensional tracking. In AC-LGADs, the AC pad is coupled to the resistive n $^{+}$ layer through a dielectric layer, while the gain layer remains unsegmented. This structure provides a 100\% fill factor and enables good spatial resolution with a relaxed readout pitch. The same signal-sharing mechanism that makes interpolation possible complicates the readout: charge spreads across multiple pads, the useful information can approach the electronic-noise threshold, and matrix-inversion approaches can become computationally challenging and sensitive to off-diagonal noise. In this work, we study machine-learning-based reconstruction and compression for resistive silicon sensors. We use full-waveform information from correlated pads to regularise the reconstruction and extract spatial information beyond what is available from binary readouts or reduced-amplitude summaries. We first introduce recurrent neural network models based on LSTM layers, which provide a proof-of-concept implementation for full-waveform reconstruction and have been tested for FPGA deployment using \hls. We also study routes towards bandwidth reduction with waveform rasterisation and window-selection methods, and extend the approach beyond the first model to topology-agnostic transformer-based architectures that use pad coordinates as part of the input. These models are designed to support arbitrary pad counts and geometries, mitigate edge distortions, preserve approximately $10 μ m$ position resolution for $500 μ m \times 500 μ m$ pitched sensors, and guide future resistive-silicon sensor designs
↳ hep-excs.LGnucl-exJINST·0 citations
13
Ab initio calculations of two-neutrino and neutrinoless double- $β$ decay of $^{48}$ Ca and related Gamow-Teller strength distributions
Zhen Li🇩🇪 · Lotta Jokiniemi🇩🇪 · Achim Schwenk🇩🇪
We present ab initio calculations of two-neutrino double-beta ( $2 ν β β$ ) decay of $^{48}$ Ca and the related Gamow-Teller (GT) strength functions in $^{48}$ Sc using the valence-space in-medium similarity renormalization group (VS-IMSRG) with nuclear interactions and electroweak currents based on chiral effective field theory. We find that the usual $p f$ -shell valence space significantly underestimates the nuclear matrix element (NME) of $2 ν β β$ decay compared to experiment, while an enlarged $d_{3/2} p f$ valence space yields very good agreement with the experimental value without any adjustments. We trace this to an improved description of the involved GT strength distributions, so that the enlarged valence space captures important correlations. The enlarged $d_{3/2} p f$ valence space leads to neutrinoless $β β$ NMEs of $^{48}$ Ca that are twice as large compared to the $p f$ -shell calculation. Our findings suggest that studies with different valence spaces and related GT strengths are important for assessing ab initio NME calculations of heavier $β β$ decays.
↳ nucl-thhep-phnucl-ex2 citations

Affiliations

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