Nuclear Theory·nucl-th

Tuesday·June 9, 2026

30 papers—13 primary·17 cross-listed

01
NICER Constraints on Low density Interpolation and High density Continuation in Neutron Star Equations of State
Federico Nola
We investigate whether current astrophysical data constrain not only the high density continuation of the neutron star equation of state, but also the low density matching procedure itself. To this end, we compare two low density branches propagated through a common high density extension and confront them with direct NICER mass-radius posteriors, a lower bound on the maximum mass, and an effective constraint on $Λ_{1.4}$ . We find that the observable predictions of the two branches remain strongly overlapping, while the NICER-informed posterior still induces a nontrivial constraint on the matching parameters. Current data therefore constrain primarily the shared continuation above $n_{1}$ , but also indirectly restrict the low-density matching sector.
nucl-thastro-ph.HE0 citations
02
Improving the Predictive Capability of the Fission Reaction Event Yield Algorithm ( $FREYA$ )
A. E. Tuckey · R. Vogt · D. Breitenmoser · S. D. Clarke · S. A. Pozzi · M. Devlin
We determine the optimal parameters for thermal neutron-induced fission of $^{233, 235}$ U and $^{239, 241}$ Pu in the complete event fission model $FREYA$ . First, we revisit and, in most cases, improve the prior values determined for spontaneous fission using a genetic algorithm. Our optimization procedure is then applied to thermal neutron-induced fission, replacing the empirically-chosen parameters previously employed in $FREYA$ . Finally, the optimized parameter values are used to make predictions for spontaneous and thermal neutron-induced fission observables not included in the fits. This work represents the first step in a broader program to study neutron-induced fission as a function of incident neutron energy, to systematically improve the performance of $FREYA$ , capturing any energy-dependent trends of the physics-based $FREYA$ parameters.
nucl-thnucl-ex0 citations
03
Clustering in hadrons and light nuclei from Lorentz boosted form factors
F.E. Rodríguez Barrera🇨🇴 · N. G. Kelkar🇨🇴
The determination of nuclear charge radii is crucial for understanding the internal structure of nuclei and their fundamental interactions. A persistent discrepancy, not only in the measured proton charge radius but also in the light nucleus charge radius, between electron scattering and muonic spectroscopy has fueled ongoing debates in nuclear and particle physics. Using this discrepancy, we revisit the role of one of the proposed solutions, namely the use of Lorentz-boosted nuclear form factors to find a subtle connection between the boost and the cluster structure of nuclei. By applying two distinct relativistic formalisms, namely the Licht-Pagnamenta and Mitra-Kumari approaches, we systematically analyze corrections to the moments of the density distributions in hadrons and nuclei. Our results demonstrate that boosting the form factors from the Breit to the rest frame of the nucleus not only assists in reconciling the spectroscopic and scattering measurements but also provides a method to infer on the quark and nucleon cluster configurations within nuclei.
nucl-thhep-phNPA(2026)·0 citations
04
The ABC classification of exotic nuclei: a proposal
L. Fortunato · A. Vitturi · G. Singh
The large number of existing nuclear species and the long list of their possible different exotic properties, such as presence of a halo (A), Borromean structure (B), clusterisation (C) and others, calls for a classification scheme that is universal, concise, categorical, informative, accessible and easily extensible. We provide here a first reasoned attempt to fill this gap with an abridged naming scheme, called $A B C$ , based on definitions and properties that characterise modern nuclear physics. We limit our chart to light isotopes with $Z \leq 10$ where most of these features appear presently.
nucl-th0 citations
05
A Dynamical Model of Light Halo Nuclei
Francisco Barranco · Gregory Potel · Enrico Vigezzi
We present a review of theoretical studies of the structure and reactions of N=7 and N=8 nuclei in the vicinity of 11Li, carried out within a framework based on Nuclear Field Theory. The coupling of valence nucleons to low-lying surface vibrations of the spherical core plays a central role, giving rise to self-energy processes that renormalize single-particle states and transfer form factors, as well as to an induced pairing interaction arising from the exchange of collective vibrations, which renormalizes the bare pairing force. Excitation spectra and cross sections for one- and two-nucleon transfer reactions populating states in the quasi-continuum are calculated and compared with available experimental data. Collective excitations in the particle-particle channel are investigated, with particular emphasis on Giant Pairing Vibrations and on their damping mechanisms arising from coupling to more complex configurations and continuum states. Comparisons with other theoretical schemes are also presented. We conclude that a coherent understanding of experimental data requires the detailed consideration of particle-vibration coupling effects.
nucl-thParticles(2026)·0 citations
06
Resonance Femtoscopy Beyond the On-Shell Approximation
Liang Zhang🇨🇳 · Tianhao Shao🇨🇳 · Song Zhang🇨🇳 · Kai-Jia Sun🇨🇳 · Yu-Gang Ma🇨🇳
The observed shift of the $Δ (1232)$ resonance peak in $π$ - $p$ femtoscopic correlations challenges the conventional Breit-Wigner description of resonances in femtoscopy. We revisit the Koonin-Pratt framework by formulating femtoscopy in the momentum-space representation. By employing the T-matrix approach to disentangle on-shell and off-shell contributions, we show that the finite spatial extent of the emission source naturally induces sensitivity to off-shell scattering dynamics. Using a Friedrichs-Lee model constrained by low-energy $π$ - $p$ scattering data, we numerically demonstrate that this off-shell sensitivity leads to a peak shift accompanied by a dip on the high-momentum side of the peak. The predicted high-momentum side dip is absent in the data, pointing to source properties beyond the simple Gaussian approximation.
nucl-thhep-ph2 citations
07
On the effect of higher order symmetry energy corrections in Skyrme models for neutron star matter
Md. Emanuel Hoque · Arunava Mukherjee
Neutron stars consist of cold, dense, neutron-rich nuclear matter under charge neutrality and $β$ -equilibrium. In most nuclear equation of state (EOS) studies, the isospin dependence of asymmetric nuclear matter is described using the conventional quadratic/parabolic approximation to the nuclear symmetry energy. However, its validity in the highly neutron-rich inner core of neutron stars remains uncertain. In this work, we systematically investigate the role of higher-order isospin corrections to the symmetry energy within the framework of Skyrme-like effective nuclear interactions. We first analyze the standard SLy4 parametrization and quantify deviations arising from successive higher-order terms in the expansion of the energy per nucleon with respect to the isospin asymmetry parameter. We then extend the analysis to a large population of physically viable Skyrme EOSs sampled over a broad parameter space constrained by conventional nuclear saturation density bounds, thermodynamic stability, and causality, as well as the requirement to support astrophysical neutron-star mass observations exceeding $2 M_{⊙}$ . We find that higher-order isospin corrections become increasingly important at supra-nuclear densities and can significantly modify composition-sensitive quantities under $β$ -equilibrium, including the neutron-proton chemical potential difference, proton fraction, leptonic sector properties, and the direct-Urca process. In contrast, the $β$ -equilibrated EOS, energy density, pressure, and sound speed remain comparatively insensitive to these corrections for most viable EOSs. Our results demonstrate that while the quadratic approximation captures bulk thermodynamic behavior reasonably well, higher-order isospin contributions play a non-negligible role in determining the detailed composition and microscopic properties of dense matter in neutron-star interiors.
nucl-thastro-ph.HEgr-qchep-th0 citations
08
Hierarchical Neural Filtering of Nuclear Mass Residuals and Spectral Signatures of Quantum Chaos
Jaskirat Singh · Chong Qi
In complex quantum many-body systems such as atomic nuclei, the interplay between regular collective motion and irregular intrinsic dynamics gives rise to fluctuations that cannot be fully captured by existing global theoretical models. Nuclear mass, which exhibits smooth trends across the nuclear chart together with localized deviations, provides a sensitive observable for investigating such irregular dynamics. In this work, we employ a variety of neural network architectures, which serve as controlled nonlinear filters within a Hierarchical Residual Decomposition framework to progressively extract and suppress the chaotic many-body signature (characterized by $1/ f$ spectral correlations) in nuclear mass residuals. The resulting Physics-Informed Neural Ensemble (PINE) model combines multiple mass models and neural network architectures, enabling a systematic suppression of coherent and chaotic components, after which the remaining fluctuations are analyzed using Fourier-based spectral diagnostics across different mass regions. Our results show that hierarchical neural residual learning efficiently removes the dominant low-frequency correlations and suppresses the quantum-chaotic spectral rigidity, driving the residuals toward the uncorrelated white-noise limit. This systematic suppression provides a quantitative diagnostic of the underlying scale-dependent complexity and many-body correlation structure of nuclear mass deviations.
nucl-th0 citations
09
Nuclear matrix element of $2 ν β β$ decay of $^{76}$ Ge: roles of high-lying states and two-body currents
Hua-Yang Xu🇨🇳 · Hao Zhou🇨🇳 · Long-Jun Wang🇨🇳
We present a microscopic analysis of the nuclear matrix element (NME) of the two-neutrino double- $β$ ( $2 ν β β$ ) decay for open-shell heavy deformed nuclei, taking into account the fact that nuclear level density increases rapidly with excitation energy as well as the contribution of two-body current (2BC). Taking $^{76}$ Ge $\to$ $^{76}$ Se decay as an example, we found that due to the rapid increase of the level density of the intermediate nucleus $^{76}$ As with excitation energy $E_{n}$ , the single- $β$ Gamow-Teller (GT) matrix elements become highly fragmented with very small magnitude, and exhibit seemingly random sign patterns at high $E_{n}$ region. This leads to an effective cancellation at high $E_{n}$ region in calculating the $2 ν β β$ NME which then turns out to converge at $E_{n} ≲ 5$ MeV, indicating that the contribution of high-lying states of the intermediate nucleus to $2 ν β β$ NME is negligible. Besides, the 2BC in the transition operator is found to contribute $\sim 10%$ quenching to the $2 ν β β$ -decay NME of $^{76}$ Ge.
nucl-th0 citations
10
Systematic study of the half-lives of nuclear bound-state $β^{-}$ decay
Jing-Wen Ran · Long-Jun Wang
Nuclear bound-state $β^{-}$ decay ( $β_{b}$ decay) is a novel weak-interaction process that becomes possible when atoms are highly ionized, such as in stellar environments or heavy-ion storage rings. In this work we present a systematic theoretical calculations for the $β_{b}$ -decay half-lives of interesting candidates for the first time, where both allowed Gamow-Teller transitions and first-forbidden transitions are taken into account by the microscopic projected shell model, and the lepton phase space is calculated by the Takahashi-Yokoi model. We analyzed the structure informations for hundreds of nuclei near the $β$ -stability line, and select 16 interesting candidates belonging to two categories, i.e., nuclei with negative $Q$ values and positive $Q$ values in neutral atoms respectively. Among these candidates, we recommend $^{243} Am^{95 +}$ , $^{194} Os^{76 +}$ , $^{227} Ac^{89 +}$ , $^{228} Ra^{88 +}$ , $^{241} Pu^{94 +}$ , $^{247} Cm^{96 +}$ and $^{250} Cm^{96 +}$ as promising ones for future studies of storage-ring experiments because their $β_{b}$ -decay half-lives are predicted to be much shorter than the half-lives in neutral atoms. These findings provide essential nuclear inputs for astrophysical models and identify specific candidates where experimental verification would be most valuable.
nucl-th0 citations
11
Hyperon polarization in isobaric Zr+Zr collisions at $s_{N N} = 200$ GeV: TRENRo3D + CLVisc with an initial longitudinal flow gradient
Ze-Fang Jiang🇨🇳 · Xiang Fan🇩🇪 · Jing Jing🇨🇳
We present a theoretical study of global and azimuthal-angle-dependent $Λ$ hyperon polarization in isobaric $_{40}^{96}$ Zr+ $_{40}^{96}$ Zr collisions at $s_{N N} = 200$ ~GeV using the TRENTo3D initial condition model coupled to the (3+1)-D viscous hydrodynamic model CLVisc. A longitudinal flow velocity gradient, controlled by $f_{v}$ , is introduced into TRENTo3D for the first time, providing an essential source of initial vorticity in this symmetric isobaric system. Within the isothermal polarization framework, the model provides a simultaneous description of STAR measurements of the global polarization $- P^{y}$ (centrality, $p_{T}$ , and $η$ dependences) and the azimuthal modulation coefficients $P_{y, c0}$ and $P_{y, c2}$ . The $p_{T}$ dependence reflects the competition between thermal vorticity and shear contributions: the thermal term decreases with $p_{T}$ , while the shear term rises and increasingly shapes the curvature of the total polarization. In this decomposition, $P_{y, c2}$ is dominantly shear-driven and serves as a clean probe of shear-induced polarization. Scans of $f_{v}$ , $k_{T}$ , and nuclear structure provide complementary constraints on the initial state, while the bulk-viscosity dependence is also examined; the five nuclear structure configurations from the STAR isobar blind analysis yield nearly indistinguishable polarization. For $P_{z}$ , the isothermal scenario captures the azimuthal modulation but overpredicts the high- $p_{T}$ modulation amplitude, and comparison with the standard thermal treatment shows that neither scenario achieves a unified description of all observables.
nucl-thnucl-ex0 citations
12
Global Ab initio Neutrino Mass Limits from Neutrinoless Double-Beta Decay
T. Shickele🇨🇦 · L. Jokiniemi🇨🇦 · A. Belley🇨🇦 · J. D. Holt🇨🇦
We present global limits for Majorana neutrino masses by combining latest results from neutrinoless double-beta ( $0 ν β β$ ) decay searches and ab initio nuclear theory. Limits are derived in a Bayesian framework utilizing likelihood functions from a suite of $0 ν β β$ -decay experiments in conjunction with nuclear matrix elements calculated from nuclear and electroweak forces derived from chiral effective field theory and implemented in the in-medium similarity renormalization group many-body approach. In contrast to nuclear models, ab initio results indicate that the current generation of $0 ν β β$ -decay experiments have likely \textit{not} yet reached sensitivities required to probe the mass regime allowed by neutrino-oscillation data, where the combined bounds are notably stronger than those given by individual experiments. Finally, from predicted sensitivities of next-generation searches, we show that, while no one individual experiment fully covers the inverted mass ordering, this can be achieved from combined contributions from the four key isotopes: $^{76}$ Ge, $^{100}$ Mo, $^{130}$ Te, and $^{136}$ Xe.
nucl-thhep-exhep-phPRD(2026)·2 citations
13
Angular and Kinetic Properties of Scission Neutrons within Time-dependent Density Functional Theory
Antonio Bjelčić · Ibrahim Abdurrahman · Kyle Godbey
Scission-neutron emission is investigated in $^{235} U (n_{th}, f)$ , $^{239} Pu (n_{th}, f)$ and $^{252} Cf (sf)$ within time-dependent density functional theory. Using a substantially larger simulation domain than in previous studies, the angular and energy distributions of emitted scission neutrons are extracted over a specific range of emission angles. At these angles, scission neutrons are absent below a threshold energy of roughly $1.5$ -- $2 MeV$ , and instead contribute predominantly to the higher energy part of the prompt fission neutron spectrum. Combining the calculated scission-neutron spectrum with a Maxwellian model for the evaporated component, constrained by low-energy experimental data, reproduces the measured high-energy prompt-fission-neutron yield in both $^{239} Pu (n_{th}, f)$ and $^{252} Cf (sf)$ , whereas the evaporation-only model systematically underestimates it. This identifies a signature of scission neutrons already present in existing high-energy prompt fission neutron spectra and constitutes direct evidence for a non-negligible scission-neutron component in prompt fission neutron emission.
nucl-th3 citations

Affiliations

first authorsco-authorsvia INSPIRE