Nuclear Theory·nucl-th

Tuesday·September 1, 2026

17 papers—7 primary·10 cross-listed

01
Strongly coupled quark matter in neutron stars and their mergers
Konstantin Maslov🇺🇸 · Ralf Rapp🇺🇸 · Joaquin Grefa🇺🇸 · Veronica Dexheimer🇺🇸 · Claudia Ratti🇺🇸
The discovery of the strongly-coupled quark-gluon plasma (sQGP) in high-energy heavy-ion collisions has revealed remarkable properties of matter at high temperature, with transport coefficients close to conjectured bounds from quantum field theory at strong coupling. The high sQGP collision rates imply very large energy uncertainties and the melting of quasiparticle structures. Deploying quantum many-body theory based on the self-consistent $T$ -matrix approach for the sQGP at high temperature, we investigate its manifestation at high baryon density and low temperature, as present in neutron stars and their mergers. We constrain the chemical-potential dependence of the quark interaction kernel using first-principles information from Quantum Chromodynamics on baryon-number susceptibilities. Very large collisional widths persist at large density and are found to relegate superconducting phases to rather small temperatures. Instead, a strongly coupled diquark liquid prevails in the thermodynamics under the conditions relevant to neutron-star mergers. At lower densities, the diquarks take over from the single-quark contributions, suggesting a pathway toward hadronization. Our results are consistent with observational constraints on the equation of state of neutron stars, corroborating the presence of strongly coupled quark matter in the interior of these objects.
nucl-thastro-ph.HEcond-mat.quant-gashep-ph0 citations
02
Local-nuclear-density dependent calculation of nucleon electromagnetic form factor ratios in finite nuclei
G. Ramalho🇰🇷 · K. Tsushima🇧🇷 · Myung-Ki Cheoun🇰🇷
We calculate the electromagnetic form factors of nucleons bound in finite nuclei and make predictions to the ratio between the electric ( $G_{E}^{*}$ ) and magnetic ( $G_{M}^{*}$ ) form factors in terms of the square of the four-momentum transfer $Q^{2}$ . We extend our previous constant-density calculations within the covariant spectator-QMC framework by incorporating the spatial nuclear density profiles of finite nuclei and quantify the deviations from the average-density approximation used in our previous applications. The impact of the medium effects can then be observed considering the ratio between $G_{E}^{*} / G_{M}^{*}$ and the ratio in free space $G_{E} / G_{M}$ , that define the proton electromagnetic double ratio associated with a given nucleus. The double ratio is expected to remove some systematic uncertainties. There is the expectation that ratios $G_{E}^{*} / G_{M}^{*}$ associated with the bound protons inside the nucleus will be measured in the near future in polarization-transfer experiments $(e A, e^{'} A^{'} p)$ . Anticipating future measurements on the subject, we make predictions for the double ratios, to be compared with the average measurements on the energy states of protons bound to nuclei. We consider the nuclei $^{12}$ C, $^{16}$ O and $^{40}$ Ca. We conclude that the form factors calculated using nuclear density profile function $ρ (r)$ are less suppressed than in the case of the results calculated using the average nuclear density. The results indicate that the relative importance of the low-density surface region increases with $Q^{2}$ , leading to a weaker suppression than that predicted by the average-density approximation. We also make predictions for the ratios associated with neutrons bound to nuclei.
nucl-thhep-exhep-lathep-ph+10 citations
03
Quantum information in neutron-proton scattering from the $M$ matrix
Linjun Xie · Jinniu Hu · Ying Zhang · Hong Shen
We study quantum-information aspects of neutron--proton scattering in the spin-space $M$ -matrix framework. Four representative classes of input states are considered, namely diagonal mixed states, separable pure states, general two-qubit pure states, and a special Schmidt-like entangled subclass. For each class, ensemble-averaged output mutual information, reduced-state linear entropy, negativity, and geometric quantum discord are calculated in the relative momentum-- scattering angle plane. The results show that the outgoing spin correlations are governed jointly by scattering kinematics and by the structure of the incoming quantum ensemble. Input states with stronger intrinsic coherence or entanglement give larger maxima and higher minima in the mutual information, negativity, and geometric quantum discord. The enhanced regions of the mutual information and geometric discord depend on the input states, while the negativity maximum remains concentrated in the high-momentum backward-scattering region. These results extend earlier studies based on product-state entanglement power and provide an ensemble-based description of how spin correlations in neutron--proton scattering arise from the interplay between input-state structure and scattering dynamics.
nucl-thquant-ph0 citations
04
NS-UNO: Neutron Star EoS Inference from an Unconstrained Number of Observations
Valéria Carvalho🇵🇹 · Márcio Ferreira🇵🇹 · Michał Bejger🇵🇱 · Constança Providência🇵🇹
Future multimessenger observations of neutron stars (NS) are expected to substantially increase both the number and precision of astrophysical constraints on the equation of state (EoS) of dense matter. This motivates inference frameworks capable of accommodating a variable, non fixed number of observations while preserving the posterior information associated with each measurement. In this work, we introduce NS-UNO, a Neural Posterior Estimation framework for NS EoS inference designed to accommodate an Unconstrained Number of Observations (UNO). NS-UNO combines a hierarchical DeepSets model with a conditional normalising flow, enabling a single trained model to perform inference from mass-radius observation sets of varying size, with each observation represented by a set of posterior samples. We demonstrate accurate and well calibrated posterior reconstructions using a model trained jointly on piecewise polytropic and non-parametric Gaussian process EoS ensembles. The reconstruction improves as observations probe a broader range of NS masses, while remaining robust to variations in the number and precision of the observations. The model also generalises to EoSs outside the families used during training. Finally, we qualitatively demonstrate the framework on current multimessenger constraints from NICER and GW170817. NS-UNO provides a flexible and scalable approach to NS EoS inference, naturally suited to the increasingly diverse observational datasets expected from next generation multimessenger astronomy.
nucl-thastro-ph.HEastro-ph.IMhep-ph0 citations
05
Production of the $ϕ$ and $Ω$ via recombination of jet parton showers in relativistic heavy ion collisions
Kyong Chol Han🇺🇸 · Sungtae Cho🇰🇷 · Su Houng Lee🇰🇷
We study the production of the $ϕ (1020)$ and $Ω (1672)$ in heavy ion collisions at $s_{N N} = 5.02$ TeV by employing two complementary approaches. In the first approach, the production of the $ϕ$ and $Ω$ is discussed in the coalescence model. In the second approach, we developed a hybrid framework that combines the recombination of shower and thermal partons with remnant string fragmentation. Thermal partons in the quark-gluon plasma are modeled using a blast-wave parameterization, while the phase space information of medium-modified parton showers is generated from Q-PYTHIA, using unquenched jet partons obtained from HIJING initial inputs. We show that both approaches agree well with the experimental measurements, and demonstrate that this hybrid framework provides deeper insight into the underlying strangeness components in the production of $ϕ$ and $Ω$ in relativistic heavy-ion collisions.
nucl-th0 citations
06
Effects of isospin imbalance on the chiral phase transition within a Chiral Dual Partner Model
R. M. Aguirre🇦🇷
The chiral symmetry is a property of the fundamental theory of the strong interaction that is relevant for the hadronic physics. It is expected that at sufficiently high temperature and matter density, this symmetry becomes manifest. Within the Chiral Dual Partner Model the chiral transformation is implemented in such a way that a fermion mass term is allowed if the parity partner of each baryon is included in the framework. This model is used here to study possible manifestations of the chiral symmetry in dense nuclear matter, assuming constant isospin fraction. It is found that the onset of the odd parity baryons is associated with two branches of thermodynamical instabilities, one of them leads to a first order phase transition for temperatures below $T_{c} ≃ 11$ MeV. An analysis of these instabilities in the phase space is given, and neutron star matter is considered as a special case.
nucl-thhep-ph0 citations
07
Electromagnetic responses induced by one- and two-body nuclear currents in inclusive electron-nucleus scattering
Kajetan Niewczas · Ashish Kumar Jha · Raúl González-Jiménez · Natalie Jachowicz · Alexis Nikolakopoulos · Jan Ryckebusch
The longitudinal and transverse nuclear response functions encode information about the electromagnetic behavior of the nuclear target probed in inclusive electron-nucleus scattering. We present a microscopic calculation based on an independent-particle model, where a non-relativistic nuclear mean-field potential governs both the initial and final hadronic states of the interaction. We add dynamically generated short-range nucleon-nucleon correlations (SRCs), as well as meson-exchange currents (MECs) derived from one-pion exchange and intermediate $Δ$ -resonance excitation. We evaluate the contributions from one- and two-nucleon knock-out reactions to nuclear responses in inclusive electron scattering from $^{12} C$ in the quasielastic and dip regions. We demonstrate that for quasielastic kinematics, SRCs quench both nuclear responses, while the MECs enhance the transverse signal, substantially improving the predicted transverse-to-longitudinal ratio. In the dip region between the quasielastic and the $Δ$ -resonance peaks, we find that the observed excess of transverse strength originates mainly from explicit two-nucleon knock-out following a $Δ$ -resonance excitation.
nucl-th0 citations
08
Machine Learning Unveils Finite-volume Energy Shifts in Three-body System
Wei-Jie Zhang🇨🇳 · Zhenyu Zhang🇨🇳 · Jifeng Hu🇨🇳 · Bing-Nan Lu🇨🇳 · Jin-Yi Pang🇨🇳 · Qian Wang🇨🇳
Finite-volume extrapolation (FVE) is essential for extracting physical observables in the lattice calculation. While rigorous FVE formulations are well established for short-range potentials in both two- and three-body systems, long-range interactions with force ranges comparable to the lattice size $L$ remain challenging. Extending a previous data-driven scheme for two-body systems, we apply symbolic regression (PySR) to uncover universal three-body FVE formulae. For short-range potentials, we reproduce the two limiting cases, i.e. $κ_{3} ≫ κ_{2}$ and $κ_{3} \sim κ_{2}$ . For pure long-range potentials, we obtain a dedicated analytic expression, and after incorporating short-range contributions, we uncover a unified formula consistent with the original PySR solution, which performs excellently in the intermediate force range around 1 fm. This work demonstrates that combining machine learning with physical constraints can yield novel analytical results inaccessible to conventional theoretical tools, advancing data-driven methodologies in hadron physics.
↳ hep-lathep-phnucl-th0 citations
09
Constrained functional priors for Bayesian inference of hot QCD matter
G. Guimarães🇧🇷 · L. Perin🇧🇷 · M. Luzum🇧🇷
Bayesian analyses of heavy-ion collisions rely on functional inputs, such as temperature-dependent transport coefficients and the equation of state, whose prior specification remains a significant source of uncertainty. Standard approaches employ low-dimensional parametrizations that can impose artificial correlations and leave the resulting inference sensitive to the assumed functional form. We develop a nonparametric framework for constructing priors over such functions using Gaussian processes, tailored to emulator-based inference in heavy-ion phenomenology. Truncated Karhunen--Loève expansions yield optimized finite-dimensional representations suitable for use as emulator inputs. We investigate how physical constraints can be incorporated into these priors, demonstrating that rejection-based methods produce non-Gaussian measures and induce nontrivial correlations in the expansion coefficients. By contrast, pushforward constructions enforce the constraints while preserving a tractable Gaussian measure in a latent space. These results provide a systematic framework for incorporating physical constraints into functional priors and clarify their effects on the statistical structure of the finite-dimensional representations used in Bayesian inference.
↳ hep-phnucl-th0 citations
10
On-shell renormalization in NREFT: a simplified description of resonances, bound states, and coupled channel effects
Guo-Ying Chen🇨🇳
We discuss several issues regarding the modern generalization of Weinberg's compositeness criterion. In particular, we demonstrate that the on-shell renormalization in NREFT reproduces Weinberg's result and provides a simple description of resonances, bound states, and coupled channel effects. Additionally, we present the complete propagator, including the charged channel for the near-threshold p-wave states.
↳ hep-phhep-exnucl-th0 citations
11
Two Languages for the Same Resonance: From Nuclear Decay to Black-Hole Ringdown
Okuto Morikawa
Quantum resonances and black-hole quasinormal modes (QNMs) are described by closely related mathematics: radiative boundary conditions, analytic continuation of Green functions or resolvents, poles on nonphysical sheets, and non-self-adjoint spectral representations. This article does not introduce that equivalence but reconstructs its genealogy. Nuclear resonance theory grew from radioactive decay, reaction cross sections, metastable compound states, and complex energies, whereas black-hole perturbation theory grew from spacetime stability and causal response. We place the two developments on a common chronology, from Sommerfeld's radiation condition and early nuclear-decay theory through Regge--Wheeler perturbations, Vishveshwara's 1968 dissertation and 1970 papers, Press's 1971 quasi-normal terminology, and the independent Aguilar--Balslev--Combes theory of analytic dilation, then follow their later mathematical reunification in scattering-resonance theory. Alongside the chronology, we give a working dictionary relating no-incoming and horizon-ingoing/infinity-outgoing conditions, pole energy and complex frequency, width and damping rate, residues and excitation factors, and nonresonant background with branch-cut and prompt contributions. The aim is to make the cross-disciplinary equivalence operational without flattening its history, and to distinguish mathematical equivalence from historical genealogy.
↳ gr-qcmath-phmath.MPnucl-th+10 citations
12
Spin-dependent fermion potentials from mixed tensor couplings of massive spin-1 and spin-2 bosons
D. Khadka🇦🇺 · V.V. Flambaum🇦🇺
Searches for weak spin-dependent forces are commonly interpreted in terms of a basis of sixteen rotationally invariant two-fermion potentials $V_{1 - 16}$ , including potentials which violate parity (P) and time-reversal (T) invariance. We derive finite-range coordinate-space potentials generated by a massive spin-1 boson with vector, axial-vector, tensor, and pseudotensor couplings to Dirac fermions. In addition to the familiar vector--vector, vector--axial-vector, and axial-vector--axial-vector interactions, we obtain the mixed vector--tensor, vector--pseudotensor, axial-vector--tensor, and axial-vector--pseudotensor potentials, together with tensor--tensor, tensor--pseudotensor, and pseudotensor--pseudotensor terms. We retain the contact terms needed in atomic-scale applications and give compact expressions that include both orderings of inequivalent fermion vertices. We then extend the analysis to a massive spin-2 mediator described by a symmetric Fierz--Pauli field. Besides the conventional coupling to the conserved fermion energy--momentum tensor, we consider a symmetric axial-tensor current. Its nonconservation for massive fermions makes the longitudinal spin-2 helicities contribute to axial-tensor--axial-tensor exchange. The leading minimal spin-2 interactions are either $P, T$ even or $P$ odd and $T$ even; in particular, they do not generate a $T$ -odd potential. Heavy-mediator contact limits and the distinction between the $M \to 0$ massive-spin-2 limit and a genuine massless graviton are also discussed. We map the new interactions onto the sixteen-potential Dobrescu--Mocioiu basis and use this mapping to obtain numerical translations of existing limits for both spin-1 and spin-2 coupling products in the small- and large-mediator-mass regimes, together with representative limits at finite mediator masses.
↳ hep-phnucl-thphysics.atom-ph0 citations
13
Meson gravitational D-form factors and symmetry breaking in low-energy QCD
Mamiya Kawaguchi🇺🇸 · Kazuhiro Tanaka🇯🇵 · Mitsuru Tanaka🇯🇵
We investigate meson gravitational D-form factors in the three-flavor linear sigma model and their connection to symmetry breaking in low-energy QCD. Within the scalar meson dominance picture, we examine the scalar meson exchange contributions and their relation to meson masses through scalar-meson couplings. In the three-flavor symmetric limit, we first derive analytical expressions for the D-form factors of pseudoscalar and scalar mesons. In the chiral limit, the forward-limit value of the octet pseudoscalar D-form factor is fixed to $- 1$ , whereas the $U (1)_{A}$ anomaly generates additional contributions to the singlet pseudoscalar and scalar-meson D-form factors. For realistic flavor breaking, the interaction introduced to reproduce the scalar-meson mass hierarchy below $1$ GeV significantly affects the scalar-meson D-form factors. We further compare the linear sigma model results with those obtained from a chiral perturbation theory Lagrangian including a dilatonic scalar field and show that their differences are governed by the canonical mass dimensions of the interaction terms contributing to meson mass generation. These results indicate that meson D-form factors provide sensitive probes of symmetry-breaking structures in low-energy hadron physics.
↳ hep-phhep-latnucl-th0 citations
14
Polarized jet anisotropy at the Electron-Ion Collider
Zhong-Bo Kang🇺🇸 · Hongxi Xing🇨🇳 · Fanyi Zhao🇺🇸 · Yiyu Zhou🇨🇳
Jets provide a powerful probe of the three-dimensional spin structure of the nucleon, a central goal of the Electron-Ion Collider. Yet the observed jet defines an axis that breaks the azimuthal isotropy of soft-gluon radiation, thereby reshaping the very asymmetries used to extract that structure. Using transverse-momentum-dependent (TMD) QCD factorization, we show for the first time that this jet-induced anisotropy imposes a parity selection rule on polarized asymmetries. Expanding the transversely polarized structure functions in harmonics $cos (n ϕ_{q J})$ , where $ϕ_{q J}$ is the angle between the jet and the lepton-jet momentum imbalance, makes this rule explicit: the symmetry of each harmonic is fixed by the parity of $n$ , independently of the magnitudes of the harmonic coefficients. For the Sivers function, the canonical left-right asymmetry about the proton spin survives for even $n$ but is replaced by a counterintuitive left-right symmetry for odd $n$ . The worm-gear function retains its up-down asymmetry at every harmonic while being left-right symmetric for even $n$ and asymmetric for odd $n$ . At EIC kinematics, the higher harmonics studied here are predicted to be individually measurable, providing new observables for the azimuthal dynamics of soft radiation and an essential ingredient in precision extractions of nucleon structure.
↳ hep-phhep-exnucl-th0 citations
15
Exploring possible $_{Λ_{c}}^{3} H$ bound states through $p Λ_{c}$ femtoscopic correlations
Ye Yan🇨🇳 · Qi Huang🇨🇳 · Qian Wu🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳
The femtoscopic correlation technique in relativistic heavy-ion collisions provides a unique opportunity to investigate hadron-hadron interactions and possible exotic states. In this work, we study the $p Λ_{c}$ correlation function and its sensitivity to the low-energy $N Λ_{c}$ interaction related to possible $_{Λ_{c}}^{3} H$ bound states. Based on the quark delocalization color screening model, three interaction scenarios with different strengths are constructed, and the corresponding spin-averaged $p Λ_{c}$ correlation functions are calculated within the Koonin--Pratt formalism. The results demonstrate that the correlation function is sensitive to the $p Λ_{c}$ interaction strength, with coupled-channel effects and $S$ - $D$ wave mixing producing additional enhancements in the correlation signal. These findings suggest that future $p Λ_{c}$ femtoscopic measurements at relativistic heavy-ion collision experiments can provide valuable constraints on the interaction between charmed baryons and nucleons and offer guidance for exploring possible heavy-flavor hypernuclei.
↳ hep-phnucl-th0 citations
16
Charmonium production in p+A collisions at SPS and FAIR energies
Taesoo Song🇩🇪 · Jiaxing Zhao🇩🇪 · Joerg Aichelin🇫🇷 · Elena Bratkovskaya🇩🇪
We employ the Parton-Hadron-String Dynamics (PHSD) transport approach to investigate the influence of baryon-rich matter on charmonium production and dissociation. The Remler formalism is implemented to dynamically model charmonium formation from charm-anticharm pairs. As a validation step, the formalism is first benchmarked against experimental data from elementary pp collisions and then extended to pA systems to extract the effective nuclear absorption cross section of charmonium. This extracted cross section can subsequently be applied in heavy-ion collisions to quantify medium-induced effects. Our results demonstrate that the Remler formalism provides a quantitatively consistent description of charmonium production in pp and pA collisions at SPS energies. The approach is then extrapolated to GSI/FAIR energies, where predictions for charmonium yields and survival probabilities are presented. These findings highlight the relevance of the Remler formalism as a dynamical framework for studying heavy-quark bound-state formation in baryon-rich matter and offer theoretical guidance for future experimental programs at SPS, FAIR and NICA aimed at mapping the QCD phase structure.
↳ hep-phnucl-th0 citations
17
Small-x TMD distributions: JIMWLK evolution and the Gaussian truncation
Florian Cougoulic🇵🇱 · Piotr Korcyl🇵🇱
We extend the systematic study of small- $x$ Transverse Momentum Dependent (TMD) distributions, initiated in [Cougoulic:2026drr], by including the energy evolution. We use the JIMWLK evolution equation to study the energy dependence of three distributions in the quark-gluon sector, $F_{q g}$ , and seven distributions in the gluon-gluon sector, $F_{g g}$ . The initial conditions are provided by the McLerran-Venugopalan model. We study these TMD distributions in position space and with $N_{c} = 3$ fixed. We then compare these results to the Gaussian truncation of the Balitsky hierarchy. Although the Gaussian truncation worked very well for the TMD distributions at the initial condition, now we identify some cases where the Gaussian truncation provides a reasonably good description, but in the majority of cases it fails to fully reproduce numerical data. Using the fixed representation building blocks, $Ω_{a g}^{ω}$ , we are able to partially explain the outcomes. This work constitutes the next step with the goal of understanding the interplays between the large- $N_{c}$ limit and Gaussian truncation as well as the BK/JIMWLK evolution equations for phenomenologically relevant observables.
↳ hep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE