Nuclear Theory·nucl-th

Fri·Sep 18, 2026Friday·September 18, 2026

11 papers—7 primary·4 cross-listed

01
Projective Origin of the Spin Hydrodynamic Attractor and Its Resurgent repeller
Qi Zhou · Enke Wang
We investigate the projective and resurgent structure of a spin hydrodynamic attractor in Bjorken expansion. We show that the nonlinear spin attractor family is determined by the projective classes of the two dimensional linear solution space, with the attractor and repeller corresponding to two distinguished projective directions and the linear modes ratio generating the full one-parameter transseries tower. We identify the attractor and repeller as complete global solution branches associated with the two distinguished projective directions of the underlying linear solution space. Using the projective transseries structure, we show analytically that the data of repeller are encoded in the Borel-Stokes structure of the attractor expansion. These results provide an explicit analytic realization of resurgence relations that are often extracted through high order expansions and numerical Borel analysis, and yield a unified description of the attractor, the repeller, and their Borel-Stokes connection in minimal causal spin hydrodynamics.
nucl-thhep-phhep-th
02
Three-State Mixing as a Phenomenological Framework for Multiple Shape Coexistence
Marco Siciliano
Shape coexistence represents one of the most striking manifestations of competing collective and single-particle degrees of freedom in atomic nuclei. While the coexistence and mixing of two configurations can be described within the well-established Two-State Mixing framework, the observation of three or more competing structures requires a more general treatment. In this work, we introduce a Three-State Mixing (3SM) model in which three intrinsic configurations are related to the physical states through an $S O (3)$ rotation. The framework establishes a direct connection between experimental observables, configuration-mixing amplitudes, and intrinsic properties, while the experimentally known excitation energies allow the corresponding effective Hamiltonian and interaction strengths to be reconstructed. The model is applied to the low-lying structure of $^{116}$ Sn using electromagnetic matrix elements recently determined through a comprehensive Coulomb-excitation measurement. The analysis identifies three intrinsic configurations characterized by spherical, weakly oblate, and strongly deformed triaxial shapes, together with substantial configuration mixing among the physical $0^{+}$ states. The present formulation provides a general phenomenological framework for investigating systems in which multiple configurations coexist and strongly interact.
nucl-thnucl-ex
03
Long-Lived False-vacuum-Trapped Self-Bound Neutron-rich Droplets
Jingdong Shao · Mei Huang
We propose a novel class of anomalous nuclear matter: self-bound, neutron-rich droplets trapped in false vacuum associated with the nuclear liquid-gas phase transition in heavy-ion collisions. During the early stage of the fireball expansion, strongly correlated local clusters dynamically decouple from the bulk medium and are excited into the liquid phase. As the ambient fireball cools rapidly, these clusters are quenched into metastable anomalous droplets with isospin asymmetry from ambient neutron-enrichment. Mechanical equilibrium among nuclear pressure difference, Coulomb repulsion, and surface tension stabilizes droplets at radii of order $O (10)$ fm. Isospin asymmetry induces high potential barrier that suppresses decay channels, yielding long lifetimes. These droplets are expected to exhibit characteristic charge-to-mass ratios distinct from conventional neutron-rich nuclei, providing clear experimental signatures for future heavy-ion collision searches.
nucl-thhep-ph
04
Interpretable hybrid nuclear mass prediction based on term-by-term model discrepancies
Weihu Ye · Niu Wan
Various theoretical mass models have consistently achieved impressive accuracy in reproducing experimental masses. However, their predictions in unmeasured neutron-rich regions exhibit noticeable model dependence. In this study, we systematically investigate the differences in model predictions by comparing the liquid-drop mass terms of two representative models. Using two widely used models, Weizsacker-Skyrme-type (WS4) and Duflo-Zuker-type (DZ10), as representative examples, we find that the differences in an isotope chain gradually become more remarkable with increasing neutron number, not only for total binding energies but also for individual mass terms. The most noticeable difference appears in the volume-symmetry energy. By leveraging the term-by-term differences between the liquid-drop energy components of WS4 and DZ10, we introduce a machine learning gating network that adaptively combines the two models to improve predictive accuracy. This conditional hybrid model achieves a lower root-mean-square deviation (rmsd) than either model alone, reducing the overall rmsd from 0.284 MeV (WS4) and 0.560 MeV (DZ10) to 0.232 MeV. In the future, this term-by-term comparison strategy can be extended to models based on density-functional theories.
nucl-th
05
Gaussian characterization of two-neutron halo nuclei
A. Deltuva · M. Gattobigio · D. Jurčiukonis · A. Kievsky
The halo nucleon-core system is, by definition, a shallow state nucleus. The nucleon, in most cases a neutron, is loosely bound to the other nucleons forming the core. Accordingly, the system is located inside the universal window; the halo nucleon most likely resides far from the rest of the nucleons, showing a remarkable insensitivity to details of the interaction with the core. The system can be described using a simple nucleon-core interaction, and this description can be extended to the nucleon-nucleon-core system. Specifically, treating the neutron-core and the neutron-neutron-core systems with a Gaussian interaction as a reference, we show trajectories inside the universal window governed by interaction parameters determined from low-energy observables, such as the neutron-core binding energy, scattering length, and effective range. In this way, we can relate properties of different halo nuclei that might seem uncorrelated. In particular, we determine the three-body parameter, the binding momentum at the unitary limit, and show that the two-neutron halo nuclei emerge from that limit following a linear trajectory depending on the neutron-core range.
nucl-thnucl-exPhysical Review C 114, 034001 (2026)
06
Bayesian calibration of a regional optical potential and uncertainty-quantified predictions for compound nucleus reactions
Samuel Sullivan · Kyle Beyer · Filomena Nunes · Paul Stevenson · James Benstead · Lee Morgan
Uncertainty-quantified global optical potential parameterizations are useful for making systematic studies across the nuclear chart and making predictions away from stability. While they generally provide a good description of the reactions on which they were calibrated, predictions can deviate strongly in specific cases and extrapolations incur large uncertainties. We propose a regional optical potential suited for a specific region of the nuclear landscape. We calibrate the potential along isotopic chains to enable both strong data coverage and improved extrapolative power. We modify the Chapel Hill optical potential and the statistical model used previously by Pruitt et al., to perform a Bayesian analysis of elastic scattering of neutrons and protons from zirconium isotopes with improved data coverage. The parameter distributions of our Chapel Hill Regional Potential (CHiRP) are propagated to compound nucleus reaction observables including (n, n'), (n, g) and (n, 2n), which have relevance to various nuclear technology applications. Results are compared to CHUQ, a global calibration of the Chapel Hill potential. The final parameterization of CHiRP differs from CHUQ particularly in the energy and radial dependence of its imaginary components. For elastic scattering, the uncertainties on the observables using CHiRP are smaller than those using CHUQ. CHiRP also provides an improvement over its global counterpart in the agreement with data around 10 MeV, while the regional and global approaches offer similar levels of agreement to elastic data at higher energies. The relative performance of CHiRP and CHUQ when propagating their uncertainty through compound nucleus reaction channels is also reported. The regional potential approach is a viable alternative to global optical model parameterizations for applications that require precise information within a sub-region of the nuclear landscape.
nucl-th
07
Probing Forward-Backward Multiplicity Correlations and Fluctuations Using the Strongly Intensive Observable $Σ$ in Pb-Pb Collisions at SPS Energies with UrQMD
Ekata Nandy · Subhasis Chattopadhyay
The strongly intensive observable $Σ$ , constructed from charged-pion multiplicities in separated forward (F) and backward (B) pseudorapidity intervals $Δ η$ , is studied within the UrQMD transport model for Pb--Pb collisions at SPS energies. The dependence of $Σ$ on $Δ η$ is investigated as a function of collision energy, centrality, and acceptance to probe the longitudinal structure of multiplicity fluctuations and correlations. For $s_{N N} > 6$ GeV, $Σ$ exhibits a non-monotonic dependence on $Δ η$ , increasing from values near unity at small separation, reaching a maximum at intermediate $Δ η$ , and decreasing towards unity at larger separation. Decomposition into scaled variance and covariance terms shows that this behavior arises from their different $Δ η$ dependences. Calculations with resonance decays switched off show that resonances dominate short-range correlations, while $Σ > 1$ at larger $Δ η$ indicates fluctuations and correlations extending over broader pseudorapidity intervals. The magnitude of $Σ$ , together with its fluctuation and covariance components, increases from central to peripheral collisions, with fluctuations dominating over covariance at large $Δ η$ . As the collision energy increases, the pseudorapidity interval over which $Σ > 1$ persists becomes significantly larger, whereas at lower energies, where resonance dynamics dominate particle production, $Σ$ is nearly independent of $Δ η$ . An acceptance-scaling study reveals deviations from simple binomial scaling in regions of strong correlations. These results demonstrate the sensitivity of $Σ$ to the interplay between multiplicity fluctuations and forward--backward correlations in heavy-ion collisions.
nucl-thhep-ph
08
Internal structure of exotic hadron candidate $f_{0}$ (980) by using fragmentation functions
S. Kumano🇨🇳
High-energy hadron reactions could be appropriate to find exotic evidences in exotic hadron candidates instead of global observables such as masses, spins, parities, and decay widths, because quarks and gluons are explicit degrees of freedom. One of possible methods is to use fragmentation functions (FFs) by taking advantage of properties on favored and disfavored functions, which corresponds to valence-quark and sea-quark distributions in parton distribution functions. Looking at these FFs, we should be able to find the exotic nature as the valence-quark distributions reflect the nature of valence constituents as shown in the pion and the proton. Recent accurate measurements of the $f_{0}$ (980) FFs by the Belle collaboration made it possible to find its internal configuration by looking at their second moments and functional forms. Global analysis results of the $f_{0}$ (980) FFs indicate that its internal configuration looks like $s s ˉ$ , which is different from a tetraquark or $K K ˉ$ -molecule like configuration suggested from low-energy studies. This fact indicates that the internal configuration looks different depending on the energy. At low energies, it looks like a tetraquark ( $K K ˉ$ molecule) hadron, but it looks like a $q q ˉ$ hadron at high energies. In the similar way, some exotic hadron candidates could become ordinary $q q ˉ$ or $q q q$ hadrons at high energies, although they are interpreted as exotic at low energies. This kind of new idea should be tested by future experiments especially by looking at energy or momentum dependencies in high energy hadron reactions.
↳ hep-ph0 citations
09
Femtoscopic Correlation Functions in Density Operator Representation
Hao-Nan Liu · Duo-Lun Ge · Zhi-Wei Liu · Jun-Xu Lu · Li-Sheng Geng
Femtoscopic correlation functions (CFs) have been increasingly used to extract strong interactions between pairs of unstable particles, but their physical soundness has recently been questioned. To answer this, we formulate CFs at the operator level, with the observed subsystem described by a reduced density operator and subsequent dynamics absorbed into an effective measurement operator. The Koonin-Pratt form is recovered under four well-motivated reductions. The formulation makes explicit that the source-side and interaction-side representations must be consistently matched, and motivates an operational convention in which a measured reference correlation establishes a compatible source--interaction pairing that can be extended to other pairs for CF-to-CF predictions.
↳ quant-phhep-exhep-phnucl-ex+1
10
Generalized parton distributions: Theory meets experiment
Yuxun Guo · Xiangdong Ji · Yao Ji · Jialu Zhang
Over the past three decades, generalized parton distributions (GPDs) have emerged as one of the most active and important areas of research in nucleon structure and quantum chromodynamics (QCD). Since the last comprehensive review two decades ago, substantial progress has been made in experimental measurements of hard exclusive processes, such as deeply virtual Compton scattering and near-threshold $J / ψ$ production, as well as in increasingly sophisticated phenomenological analyses of GPDs that enable three-dimensional nucleon tomography. Theoretical advances in perturbative coefficient functions, scale evolutions, and kinematic and power corrections have considerably improved the precision of GPD phenomenology, while new hard exclusive processes for probing GPDs have been explored. More interestingly, lattice QCD can now directly access GPDs at fixed parton momentum fractions $x$ and skewness $ξ$ through large-momentum expansions, in addition to the traditional calculations of their moments, or generalized form factors. Significant progress has also been made in exploring the QCD energy-momentum tensor that encodes fundamental information on the nucleon's mass distribution, complete spin structure, and spatial distributions of momentum current and color-Lorentz forces acting on quarks and gluons.
↳ hep-phhep-exhep-latnucl-ex+1
11
Higher twists in QCD
W. Melnitchouk
Higher twists in deep-inelastic scattering (DIS) and related hard scattering processes provide a unique window on nonperturbative QCD dynamics, encoding quark-gluon correlations and multiparton interactions beyond the leading-twist parton model. We present an overview of the theoretical foundations of higher twists in QCD, based on the operator product expansion, and discuss their intimate connection with quark-hadron duality in the transition between the resonance and scaling regimes. We review the phenomenology of higher-twist effects in unpolarized and polarized DIS, emphasizing their extraction from precision data through modern global QCD analyses that simultaneously determine both leading-twist parton distribution functions and higher-twist contributions. Finally, we discuss recent developments in the study of higher twists in semi-inclusive and exclusive reactions, and conclude by highlighting future opportunities to study QCD dynamics beyond leading twist at Jefferson Lab and the Electron-Ion Collider that promise to deepen our understanding of hadron structure.
↳ hep-phhep-exnucl-th

Affiliations

first authorsco-authorsvia INSPIRE