Nuclear Experiment·nucl-ex

Tue·Jun 30, 2026Tuesday·June 30, 2026

10 papers—2 primary·8 cross-listed

01
Dineutron clusters
Takashi Nakamura · Kouichi Hagino🇯🇵 · Yosuke Kondo
The dineutron is a spatially compact two-neutron cluster, which is expected to appear in a low-density part of nuclei. In recent years, there has been rapid progress in experimental and theoretical research on dineutron clusters, particularly on neutron-rich rare isotopes. Experimentally, evidence for dineutron in two-neutron halo nuclei, such as $^{11}$ Li, has been obtained using Coulomb breakup, measurements of charge radii, and quasi-free proton scattering. Specific unbound nuclei just beyond the neutron drip line, which decay by emitting two neutrons, are also candidates for having a dineutron correlation. For instance, the dineutron structure has recently been investigated for $^{16}$ Be, focusing on its decay into the core and the two neutrons. Theoretically, it is shown that the dineutron is partially due to the admixture of different-parity configurations for the two valence neutrons. Few-body theories, including dynamical effects of the decay process, play important roles in interpreting three-body decays. We also discuss the four-neutron clusters, showing the experimental results of recent tetraneutron experiments and observation of $^{28}$ O. Possible relevance of these states to dineutron correlation is discussed. Finally, we discuss future perspectives on dineutron clusters in neutron-rich nuclei and their relation to the universal features in few-body physics.
nucl-exnucl-thphysics.atom-phEPJA(2026)·2 citations
02
Precision measurement of radiative neutron \b{eta}-decay: methodology and systematic effects
J.S. Nico🇺🇸 · R. Alarcon🇺🇸 · M.J. Bales🇺🇸 · C.D. Bass🇺🇸 · E.J. Beise🇺🇸 · H. Breuer🇺🇸 · T.E. Chupp🇺🇸 · K.J. Coakley🇺🇸 · R.L. Cooper🇺🇸 · M.S. Dewey🇺🇸 · S. Gardner🇺🇸 · T.R. Gentile🇺🇸 and 9 other authors
In the Standard Model the free neutron decays to a proton, an electron, and an antineutrino along with a continuous spectrum of photons. In 2016 the RDK II collaboration reported on a measurement of the photon energy spectrum and branching ratio over the range of 0.4 keV to the 782 keV endpoint using two different detector arrays. In the experiment, the radiative decay photons were observed in coincidence with the decay electrons and protons. In this paper, we present details of the analysis, including the determination of the systematic corrections and uncertainties and comparison of measured particle and photon energy spectra to Monte Carlo simulations. We conclude with approaches to improving the precision of these measurements.
nucl-ex0 citations
03
Multistage dynamical modeling of heavy-ion collisions
Lipei Du🇺🇸
Relativistic heavy-ion collisions create deconfined QCD matter whose properties must be inferred from final-state observables through dynamical modeling. This contribution discusses recent progress and open issues in multistage simulations, with emphasis on the connection between bulk evolution, conserved charges, strangeness, and heavy flavor. At RHIC Beam Energy Scan energies, the breaking of longitudinal boost invariance makes charge stopping and rapidity-dependent observables essential for constraining the finite-density medium. Strange hadrons are sensitive to the local chemical environment and conserved-charge correlations, while heavy flavor probes microscopic transport and hadronization. Combining these observables within multi-sector inference frameworks provides a path toward more robust constraints on the equation of state and transport properties of QCD matter.
↳ nucl-thhep-phnucl-ex1 citation
04
Soft Contributions Stabilize NNLO QCD Corrections to Quarkonium Production and Decay
Luca Maxia🇫🇷 · Hua-Sheng Shao🇫🇷 · Lukas Simon🇫🇷 · Guoxing Wang🇫🇷
Next-to-next-to-leading order (NNLO) QCD corrections to quarkonium production and decay are known to exhibit perturbative instabilities within non-relativistic QCD. We identify the origin of this problem and propose a simple remedy. Applying our approach to $S$ -wave color-singlet quarkonium processes, we achieve substantially improved perturbative convergence and agreement with experimental data.
↳ hep-phhep-exnucl-exnucl-th2 citations
05
Thermal and electromechanical response of ultra-thin carbon-strip polarimeter targets in relativistic bunched beams
F. Rathmann🇺🇸 · O. Eyser🇺🇸 · M. Sangroula🇺🇸 · P. Shanmuganathan🇺🇸 · V. Shmakova🇺🇸
Thin carbon-strip targets provide fast relative hadron beam polarimetry, but their response in intense relativistic bunched beams is not governed by local stopping-power heating alone. We develop a coupled response model that combines beam-target overlap, secondary-electron escape, retained heat, target motion, transient heat transport, RF-induced strip-end heating, beam-induced forces, resistance changes, and slack-strip deformation. RHIC target observations constrain the relevant motion, force, and nonlocal-heating scales and show that target survival depends on both beam-center heating and electromagnetic boundary conditions near the strip ends. Applying the model to Booster, AGS, RHIC, and EIC proton and $^{3} He$ cases shows that the RHIC proton lifetime scale is reproduced at the order-of-magnitude level, while the RHIC target-holder fin results require the additional RF/end-heating mechanism. For EIC proton flattop operation, carbon-strip polarimetry may remain viable only with reduced dwell time, sufficient detector acceptance, and suppression of RF-induced end heating. For cooled-emittance $^{3} He$ , the calculated sublimation-loss scale is far beyond a straightforward RHIC-like carbon-strip extrapolation. Conventional carbon strips are therefore unlikely to remain viable for the most demanding EIC light-ion cases without major changes in target motion, target technology, or diagnostic concept.
↳ physics.acc-phnucl-ex0 citations
06
Self-Supervised Calibration of Scientific Instruments Using Physical Consistency Constraints
M. Rejmund🇫🇷 · A. Lemasson🇫🇷
Calibration remains one of the principal obstacles to the deployment of machine learning in scientific instrumentation because it typically relies on expert intervention, dedicated procedures, and manually labelled data. We introduce a physics-informed self-supervised framework that jointly learns latent detector calibration parameters and task-specific predictions directly from raw measurements without requiring pre-calibrated signals or external labels. The method exploits known physical constraints to generate pseudo-labels iteratively, transforming calibration into a self-supervised optimization problem. The approach is demonstrated for ionic charge-state determination in the VAMOS++ magnetic spectrometer, where the calibration of a segmented ionization chamber and the inference of ionic charge states are learned simultaneously. Starting from a weak prior on the mean ionic charge state, the model progressively refines its predictions through iterative fractional pseudo-labelling driven by the discrete nature of atomic masses. Beyond accurate ionic charge-state reconstruction, the inferred calibration coefficients provide a compact representation of the detector state that enables automated monitoring of gain drifts, pressure variations, and detector aging. The resulting labels can subsequently be transferred to specialized models that quantify detector imperfections and track their spatial and temporal evolution. These results establish a general paradigm for self-calibrating and self-monitoring scientific instruments and represent a step toward intelligent experimental systems capable of autonomous calibration, analysis, and performance optimization.
↳ cs.LGnucl-exphysics.ins-det0 citations
07
Nuclear equation-of-state at high density and multi-messenger astronomy: contribution of heavy-ion collisions
A. Le Fèvre🇩🇪
In the past decades, heavy-ion collisions (HIC) at intermediate energies have allowed to probe the nuclear equation-of-state (EoS) of both symmetric and asymmetric nuclear matter over a broad range of densities. In particular, flow has proven to be a powerful observable. Combining the symmetry energy and the symmetric nuclear matter constraints of the EoS from HIC allowed to predict a density dependence of the pressure in a neutron star, up to about 2.5 times saturation density ( $n_{s a t}$ ), which agrees with recent astronomical measurements deduced from gravitational waves and pulsar observations. So far, the accuracy from HIC expectations is comparable to the latter up to 1.5 $n_{s a t}$ . In these studies, a fundamental aspect is the determination of the profile of densities that are probed by experimental observables used to constrain the EoS. In the near future, new experiments like ASY-EOS performed at higher incident energy and with better accuracy will push further the frontier of the knowledge of the symmetry energy at higher density. These efforts cannot be conclusive without a reliable uncertainty determination, which is related to the reliability of transport model dependencies. Improvements and breakthroughs in transport model simulations and nuclear theory are therefore expected in a joint effort towards HIC contributions to the field of neutron-star physics, including the contribution of strangeness and of the QCD phase transition.
↳ nucl-thastro-ph.HEnucl-ex2 citations
08
Quark--hadron duality in inclusive electron--proton scattering at high $Q^{2}$ : structure functions and truncated moments from CLAS12
Y. Wunderlich🇺🇸 · A. Bulgakov🇺🇸 · K. Joo🇺🇸 · T.-S. H. Lee🇺🇸 · V. I. Mokeev🇺🇸
We present a high-precision study of quark--hadron duality in inclusive electron--proton scattering in the nucleon resonance region, extending to $Q^{2} \approx 10 GeV^{2}$ , based on recent CLAS12 cross-section measurements at Jefferson Lab. The data, taken with a 10.6~GeV beam, span $2.55 \leq Q^{2} \leq 10.4 GeV^{2}$ and cover the full resonance region up to $W \approx 2.5 GeV$ . To reach the CLAS12 kinematics, we develop a phenomenological high- $Q^{2}$ extension of the Argonne--Osaka (ANL-Osaka) dynamical coupled-channels framework, anchored to the original calculation at $Q_{0}^{2} = 2.774 GeV^{2}$ and constrained by the measured cross sections. This enables an ANL-Osaka-constrained longitudinal--transverse decomposition and determination of the proton structure function $F_{2} (W, Q^{2})$ , from which we evaluate $W$ -truncated Cornwall--Norton moments $M_{2} (Q^{2})$ . Comparison with the CJ15 global QCD analysis, including target-mass and higher-twist corrections, shows consistency at the cross-section, structure-function, and truncated-moment levels, providing quantitative evidence for both local and global quark--hadron duality at substantially higher $Q^{2}$ than previously explored. We further identify a threshold effect in the partonic calculation: the finite- $Q^{2}$ corrections do not enforce the physical pion-production threshold, and the residual discrepancy in the first resonance region is consistent with this effect rather than a breakdown of duality. Within the coupled-channel description, the single-pion channel alone underestimates the inclusive resonance-region strength above the $Δ (1232)$ , which is carried predominantly by the multi-meson channels, as required for duality.
↳ hep-phnucl-ex0 citations
09
Isospin-Driven Splitting of Chemical Potentials in Isobar Collisions from Lattice QCD
Heng-Tong Ding🇨🇳 · Jin-Biao Gu🇨🇳 · Arpith Kumar🇨🇳 · Jia Ni🇨🇳
Strong magnetic fields produced in relativistic heavy-ion collisions can modify fluctuations of conserved charges and, consequently, their associated chemical potentials. We present first-principles $(2 + 1)$ -flavor lattice-QCD results for isospin-driven splittings of conserved-charge chemical potentials between the isobar systems $_{44}^{96} Ru +_{44}^{96} Ru$ and $_{40}^{96} Zr +_{40}^{96} Zr$ in the QCD crossover region, both at vanishing and nonzero magnetic fields along the pseudo-critical line $T_{p c} (e B)$ . We outline a framework that, under strangeness neutrality and charge-to-baryon ratio $r \equiv n_{Q} / n_{B}$ , maps the isospin difference between two nuclei, as encoded in $r_{Zr}$ and $r_{Ru}$ , onto splitting ratios $Δ μ_{Q} /Δ μ_{B}$ , $Δ μ_{S} /Δ μ_{B}$ , and $Δ μ_{S} /Δ μ_{Q}$ as functions of $μ_{B} (r_{Ru}) /Δ μ_{B}$ . Using continuum-estimated lattice results for the leading-order coefficients $q_{1} \equiv (μ_{Q} / μ_{B})_{LO}$ and $s_{1} \equiv (μ_{S} / μ_{B})_{LO}$ , we find that, at vanishing magnetic field, the splitting ratios are of similar magnitude to recent Bayesian extractions from STAR isobar data and yield $Δ μ_{Q} < 0$ and $Δ μ_{S} > 0$ , with the electric-charge sector dominating. At nonzero magnetic fields, the splitting ratios show only moderate $e B$ dependence. We therefore further examine Ru--Zr differences in the normalized magnetic-field response of chemical-potential ratios, particularly those involving $μ_{Q} / μ_{B}$ , which display a pronounced enhancement in lattice QCD. We also present hadron resonance gas (HRG) results and experimentally motivated proxy observables with kinematic cuts to facilitate contact with experiment.
↳ hep-lathep-phnucl-exnucl-th1 citation
10
Bayesian Analysis with Markov Chain Monte Carlo for Global Optimization and Degeneracy Diagnosis in Nuclear Mass Models
Xiangnan Lee · Yi Hua Lam🇨🇳 · Zi-Ao Zhang · Jayke Ren
We employ a full Bayesian analysis with adaptive Metropolis-Hastings Markov chain Monte Carlo (BA-MCMC) sampling to systematically study the posterior probability distributions of the strengths of energy terms in optimized nuclear mass models of Bethe-Weizsäcker variants. Strong correlations of some energy terms for some mass models are revealed through the parameter degeneracy diagnosis. We analyze selected refined models to determine parameter degeneracies while proposing a new macroscopic-microscopic mass model, BWL, which considers quadrupole and high-multipole deformation and shell corrections. All mass models in this work are analyzed and optimized through the BA-MCMC method. Compared with 2242 precise experimental binding energies of AME2020, BWL produces a root-mean-square deviation of 759 keV, particularly improving the description of masses in the light-nuclei and actinide regions. BA-MCMC offers robust inference on parameter degeneracy while providing an optimization method for future nuclear mass models.
↳ nucl-thnucl-ex0 citations

Affiliations

first authorsco-authorsvia INSPIRE