Nuclear Theory·nucl-th

Tuesday·December 9, 2025

17 papers—9 primary·8 cross-listed

01
The influence of heavy quark potential on quarkonium production in quark-gluon plasma
Taesoo Song🇩🇪 · Jiaxing Zhao🇩🇪
Remler formalism is the Wigner projection of a two particle state to bound states, which is carried out when the bound state begins to exist or when one of the two particles scatters in medium. This method has been successfully applied to quarkonium production in box simulations and in heavy-ion collisions. In this study this method is extended to strongly bound states with considerable binding energies by taking into account the potential energy between heavy quark pairs in the quark-gluon plasma (QGP). We find that an attractive heavy-quark potential enhances quarkonium production and the results are consistent with those from the statistical model in box simulations, if a proper spatial cutoff is introduced to the potential to mimic quantum effects.
nucl-thPRC(2026)·4 citations
02
Understanding Charge Radii with Machine Learning: Discovering Physics Expressions
B. Maheshwari🇫🇷 · P. Van Isacker🇫🇷
We introduce a robust, interpretable machine learning (ML) framework that combines numerical regression for high-accuracy predictions with symbolic regression to uncover the underlying physics. This hybrid approach effciently derives analytical expressions by leveraging the smoothed predictions of optimized ML models, a significant acceleration over direct symbolic regression on raw experimental data. We apply this framework, as an example, to nuclear charge radii across the nuclear chart, notably including light nuclei that are often excluded from such studies. We employ Light Gradient Boosting Machine (LGBM) and Gaussian Process Regression (GPR) models to map correlations between charge radii and key physical features: mass $A^{1/3}$ and proton number $Z^{1/3}$ dependencies, total binding energy, and for the first time, the pairing gap. Our models are rigorously trained using four-fold cross-validation with automated hyperparameter optimization, ensuring robustness and generalizability, which is critical for the typically small and skewed datasets in nuclear physics. Finally, we distill the knowledge from the initial LGBM and GPR models into simplified, interpretable mathematical expressions via symbolic regression, white-boxing these ML models. The derived formulas provide physical insights comparable to traditional many-body models and demonstrate a powerful pathway for physics expression discovery guided by ML.
nucl-thnucl-exPLB(2026)·2 citations
03
Direct Boundary Matching: A Bound-State Technique for Nuclear Scattering with Lagrange-Legendre Functions
Jin Lei
I present a direct boundary matching method (DBMM) for solving nuclear scattering problems using Lagrange-Legendre basis functions. This approach belongs to the family of bound-state techniques for the continuum, reformulating scattering problems into a localized, square-integrable ( $L^{2}$ ) representation. The key feature is the direct incorporation of the outgoing wave boundary condition into the last row of the matrix equation, eliminating the need for Bloch operators and two-step matching procedures required in traditional R-matrix methods. Unlike the complex scaling method that rotates coordinates into the complex plane, DBMM operates entirely in real coordinate space. The formalism is extended to coupled-channel problems, where the wave function decomposition naturally leads to an effective source potential that distinguishes between the entrance channel and other channels. Benchmark calculations for p~+~ $^{12}$ C scattering demonstrate excellent agreement with the Numerov integration method.
nucl-thPRC(2026)·2 citations
04
Bayesian Inference of Heavy-Quark Dissipation and Jet Transport Parameters from D-Meson observables in heavy-ion collisions at the LHC energies
Xu-Fei Xue🇨🇳 · Zi-Xuan Xu🇨🇳 · Wei Dai🇨🇳 · Jiaxing Zhao🇩🇪 · Ben-Wei Zhang🇨🇳
We perform the first simultaneous Bayesian inference of the temperature-dependent heavy-quark spatial diffusion coefficient $2 π T D_{s}$ and the scaled jet transport coefficient $q^/ T^{3}$ in the quark-gluon plasma, utilizing $D$ -meson nuclear modification factor $R_{AA}$ and elliptic flow $v_{2}$ data from Pb-Pb collisions at $s_{NN} = 5.02 TeV$ . The analysis employs a unified improved Langevin transport model that incorporates both collisional and radiative energy loss, followed by coalescence plus fragmentation hadronization. The posterior distributions of the parameters of $q^/ T^{3}$ and those of $2 π T D_{s}$ are well constrained, and compared with the results of theoretical models or other experimental data extraction, respectively. The $30 - 50%$ centrality data provide significantly stronger constraints than the $0 - 10%$ data. The extracted ratio $q^/ κ$ between the quark jet transport and heavy-quark diffusion coefficients exhibits a non-monotonic temperature dependence, deviating from the value $2$ estimated from the definition, with a value interval spanning 0.25--0.8 corresponding to the mean values of the inferred parameters. This work establishes a data-driven quantitative relationship between these two fundamental transport properties in the same observables, offering crucial insight into their interplay in the strongly coupled medium.
nucl-thhep-phPRC(2026)·3 citations
05
Shell-model calculation with density-dependent interaction for $p f$ -shell nuclei
K. Yoshinaga · N. Shimizu · T. Nakatsukasa
Shell-model calculations with density-dependent interactions are performed to investigate $p f$ -shell nuclei, examining the ground-state energies, low-lying spectra, and $E 2$ transition probabilities. The density-dependent terms in the interaction are self-consistently determined using the shell-model wave function for the ground state. We test three density-dependent interactions adapted from density functionals of Gogny-D1S, Gogny-GT2, and M3Y-P6. The shell-model results satisfactorily agree with the experimental data. However, the Gogny-D1S and Gogny-GT2 fail to reproduce the magicity of $N = 28$ , while it is properly described by the M3Y-P6 functional.
nucl-thPTEP(2026)·0 citations
06
Absence of charged pion condensation in a magnetic field with parallel rotation
Puyuan Bai🇨🇳 · Lianyi He🇨🇳
We investigate the critical temperature of a relativistic Bose-Einstein condensate of charged bosons driven by rotation in a parallel magnetic field [Y. Liu and I. Zahed, Phys. Rev. Lett. 120, 032001 (2018)]. For non-interacting bosons, the critical temperature can only be determined for a system with fixed angular momentum. We find that the critical temperature of the non-interacting system vanishes due to the fact that the system is quasi-one-dimensional, indicating that non-interacting bosons cannot undergo Bose-Einstein condensation. For interacting bosons, we investigate a system with quartic self-interaction. We show that the order parameter vanishes and the off-diagonal long-range order is absent at any nonzero temperature because of the quasi-one-dimensional feature, in accordance with the Coleman-Mermin-Wagner-Hohenberg theorem.
nucl-thcond-mat.quant-gashep-thPRD(2026)·4 citations
07
Gamow shell model predictions for six-proton unbound nucleus $^{20}$ Si
J.L. Wang · M.R. Xie · K.H. Li · P.Y. Wang · N. Michel · Q. Yuan · J.G. Li
Proton-rich nuclei beyond the proton drip line are of great interest in nuclear structure physics, due to exotic phenomena such as proton emissions and the Thomas-Ehrman shift (TES). In this work, we employ the Gamow shell model (GSM) to investigate the structure and decay of $^{20}$ Si, a candidate for six-proton (6 $p$ ) emission, which can be produced via two-neutron knockout from the drip line nucleus $^{22}$ Si. We predict that its ground state decays via $6 p$ emission to the ground state of $^{14}$ O, with a decay energy $E_{6 p} = 10.125$ MeV and a width of 371~keV. A $2^{+}$ state is predicted at 1.7 MeV, comparable with that in $^{18}$ Mg, indicating the disappearance of the $Z = 14$ magic number in $^{20}$ Si. Instead, analyses of the many-body configurations and the average occupancies of the mirror states suggest the presence of $d y nami c$ TES in low-lying states of $^{19}$ Al/ $^{19}$ C and $^{20}$ Si/ $^{20}$ C. Further evidence is provided by analyzing the contributions of different components of the GSM Hamiltonian. Moreover, this study offers the first theoretical description of $^{20}$ Si and guidance for future experiments.
nucl-thPLB(2026)·4 citations
08
Generalised Bohr Hamiltonian for Gogny interactions
C. Azam🇫🇷 · D. Davesne🇫🇷 · Y.Lallouet🇫🇷 · L. Próchniak🇵🇱 · M. Frosini🇫🇷 · A.Pastore🇫🇷
Using a generalised Bohr Hamiltonian formalism together with the Gogny interaction to provide a microscopic input of the required mass parameters, we present the potential energy surface and the evolution of the first excited 2 $^{+}$ state for the gadolinium isotopic chain. We observe that the energies and electromagnetic transitions of low-lying states are fairly similar for the various parametrisations and are in good agreement with experimental data.
nucl-thActa Phys.Polon.Supp.(2026)·0 citations
09
Trapped Fermions Through Kolmogorov-Arnold Wavefunctions
Paulo F. Bedaque · Jacob Cigliano · Hersh Kumar · Srijit Paul · Suryansh Rajawat
We investigate a variational Monte Carlo framework for trapped one-dimensional mixture of spin- $\frac{1}{2}$ fermions using Kolmogorov-Arnold networks (KANs) to construct universal neural-network wavefunction ansätze. The method can, in principle, achieve arbitrary accuracy, limited only by the Monte Carlo sampling and was checked against exact results at sub-percent precision. For attractive interactions, it captures pairing effects, and in the impurity case it agrees with known results. We present a method of systematic transfer learning in the number of network parameters, allowing for efficient training for a target precision. We vastly increase the efficiency of the method by incorporating the short-distance behavior of the wavefunction into the ansätz without biasing the method.
nucl-thcond-mat.dis-nncond-mat.quant-gasphysics.comp-ph+11 citation
10
The phases of QCD reached in terrestrial and cosmic colliders
Sourendu Gupta🇮🇳
We review the current state of knowledge of the phase diagram of QCD through lattice, effective field theories, and chiral models. Several sections through the three dimensional phase diagram are known for $N_{f} = 2 + 1$ with good precision. Due to technical advances in lattice techniques over the last decade or so, new aspects of the phase diagram can now be explored. We review current lattice results. The newly acquired knowledge can be used to reconstruct the full phase diagram for physical QCD, \ie, $N_{f} = 1 + 1 + 1$ . We remark on the computations which would help understand this better, and what the current constraints are on matter in neutron star cores. We also remark on the physics of the chiral transition and neutron stars in the 't Hooft large $N_{c}$ limit.
↳ hep-latastro-ph.HEhep-phnucl-th0 citations
11
Inferring the breakdown scales of the chiral expansions for $g_{A}$ and $m_{N}$
Andreas Ekström🇸🇪 · Daniel R. Phillips🇺🇸 · Lucas Platter🇺🇸 · Matthias R. Schindler🇺🇸
We apply Bayesian inference to the order-by-order chiral perturbation theory ( $χ$ PT) expansions for the axial-vector coupling constant $g_{A}$ and the nucleon mass m_N, and thereby infer the scales at which $χ$ PT breaks down for these two observables. Using a pointwise Bayesian analysis, we find that the inferred breakdown scales are notably different for the two observables. For the chiral expansion of $g_{A}$ , we obtain $25 1_{- 50}^{+ 20}$ MeV and $21 1_{- 30}^{+ 20}$ MeV using two distinct sets of low-energy constants, while for the chiral expansion of $m_{N}$ we infer a significantly larger breakdown scale of $49 1_{- 90}^{+ 60}$ MeV.
↳ hep-phnucl-thPLB(2026)·3 citations
12
Photon emission from weakly magnetized neutral pions
Xinyang Wang🇨🇳 · Fan Lin🇨🇳 · Igor Shovkovy🇺🇸
Using a hadronic framework, we derive an explicit expression for photon production from neutral pions in a weak background magnetic field. Our calculation is built on the proton triangle diagram with an effective Yukawa $π^{0}$ -proton coupling, offering an alternative to quark-level descriptions that is advantageous when the magnetic length greatly exceeds the proton size. Corrections to the pion decay constant are computed up to second order in the magnetic-field strength, revealing that the field generally suppresses the decay rate. Quantitatively, however, the effect remains modest even for fields as strong as $∣ e B ∣ ≃ m_{π}^{2}$ . The differential photon emission rate exhibits anisotropy, with the strongest suppression occurring when the pion momentum is perpendicular to the magnetic field. Overall, the modification of the $π^{0} \to γ γ$ rate is parametrically small, scaling as $∣ e B ∣^{2} / m_{P}^{4}$ , where $m_{P}$ is the proton mass. While the magnetic-field-induced anisotropy is conceptually interesting in principle, it is likely too small to be resolved in present heavy-ion measurements.
↳ hep-phnucl-thPRD(2026)·1 citation
13
Maximally Symmetric Boost-Invariant Solutions of the Boltzmann Equation in Foliated Geometries
Mauricio Martinez🇺🇸 · Christopher Plumberg🇺🇸
In this work we study the relativistic kinetic theory of a boost-invariant conformal gas on a static, maximally symmetric background $d S_{3} \times R$ , considering all constant-curvature slicings of $d S_{3}$ - flat, spherical, or hyperbolic- and their associated symmetry groups. Using a symmetry-driven cotangent-bundle approach, we show that the isometry group of each slicing acts on phase space in such a way that only its Casimir invariants and the time-like coordinate unconstrained, so the distribution function depends solely on these quantities. This yields a unified boost-invariant exact solution of the Boltzmann equation valid for each constant-curvature foliation of $d S_{3} \times R$ . Specializing this general solution to the flat and spherical foliations reproduces the Bjorken and Gubser flows, respectively, while its restriction to the hyperbolic foliation produces a genuinely new analytic solution (`Grozdanov flow'). Hydrodynamics and free streaming emerge naturally as limiting regimes of this novel exact solution. We further comment on several relevant aspects of the new boost-invariant solution on the hyperbolic slicing and on their interpretation once mapped back to Minkowski space.
↳ hep-thcond-mat.stat-mechgr-qchep-ph+1PRD(2026)·2 citations
14
Identified charged hadron production in Au+Au collisions at $s_{NN}$ = 54.4 GeV with the STAR detector
STAR Collaboration: B. E. Aboona🇺🇸 · J. Adam🇨🇿 · G. Agakishiev🇷🇺 · I. Aggarwal🇮🇳 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · A. Aitbayev🇷🇺 · I. Alekseev🇷🇺 · E. Alpatov🇷🇺 · A. K. Alshammri🇺🇸 · A. Aparin🇷🇺 · S. Aslam🇨🇳 and 375 other authors
We present results on the production of $π^{\pm}$ , $K^{\pm}$ , $p$ , and $p ˉ$ in Au+Au collisions at $s_{NN}$ = 54.4~GeV using the STAR detector at RHIC, at midrapidity ( $∣ y ∣ <$ 0.1). Invariant yields of these particles as a function of transverse momentum are shown. We determine bulk properties such as integrated particle yields ( $d N / d y$ ), mean transverse momentum ( $⟨ p_{T} ⟩$ ), particle ratios, which provide insight into the particle production mechanisms. Additionally, the kinetic freezeout parameters ( $T_{kin}$ and $⟨ β_{T} ⟩$ ), which provide information about the dynamics of the system at the time of freezeout, are obtained. The Bjorken energy density ( $ϵ_{BJ}$ ), which gives an estimate of the energy density in the central rapidity region of the collision zone at the formation time $τ$ , is calculated and presented as a function of multiplicity for various energies. The results are compared with those from the models such as A Multi-Phase Transport (AMPT) and Heavy Ion Jet INteraction Generator (HIJING) for further insights.
↳ nucl-exhep-exhep-phhep-th+1PRC(2026)·2 citations
15
Nucleon 3D intrinsic spin structure from the weak-neutral axial-vector form factors
Yi Chen
Relativistic 3D weak-neutral axial-vector four-current and spin distributions inside a nucleon (or a general spin- $\frac{1}{2}$ hadron) including three weak-neutral axial-vector form factors are investigated for the first time. We clarify that the relativistic 3D axial charge distribution in the Breit frame is completely described by the induced pseudotensor form factor $G_{T}^{Z} (Q^{2})$ rather than by the axial form factor $G_{A}^{Z} (Q^{2})$ . We demonstrate that $R_{A} \equiv \frac{- 6}{G _{A}^{Z} ( 0 )} \frac{d G _{A}^{Z} ( Q ^{2} )}{d Q ^{2}}_{Q^{2} = 0}$ can not be interpreted as the physically meaningful 3D root-mean-square axial radius of a spin- $\frac{1}{2}$ hadron. The genuine axial radius for any spin- $\frac{1}{2}$ hadron in fact does not exist. We also show that the relativistic 3D weak-neutral spin radius $r_{spin} = ⟨ r_{spin}^{2} ⟩$ , with $⟨ r_{spin}^{2} ⟩ \equiv R_{A}^{2} + \frac{1}{4 M ^{2}} [1 + \frac{2 G _{P}^{Z} ( 0 )}{G _{A}^{Z} ( 0 )}]$ based on the relativistic and intrinsic 3D weak-neutral spin distribution in the Breit frame, is a physically meaningful radius that can be unambiguously defined for the nucleon, which provides an additional key motivation for the further determination of the induced pseudoscalar form factor $G_{P}^{Z} (Q^{2})$ . Numerically, we find that $R_{A} \approx 0.6510 fm$ , $r_{spin} \approx 2.1054 fm$ and $r_{spin} \equiv r_{spin} /3 \approx 0.7018 fm$ . For future experimental measurements of $G_{A}^{Z} (Q^{2})$ and $G_{T}^{Z} (Q^{2})$ , we also derive the full tree-level unpolarized differential cross sections for neutrino-proton and antineutrino-proton elastic scattering in the lab frame, in hoping to provide a complementary and new perspective to unveil the nucleon spin structure by using (anti)neutrino-based facilities.
↳ hep-phhep-thnucl-th1 citation
16
Chiral, parity-doublet, effective-Lagrangian mean-field theories for nuclear and astrophysical phenomenology
Ayon Mukherjee🇮🇳
Chiral-parity (parity-doublet) effective Lagrangian models provide a compact and symmetry-consistent framework for describing baryons and their negative-parity partners in terms of linearly-realized chiral symmetry. Unlike the conventional, linear, sigma model; the parity-doublet approach accommodates a chirally-invariant mass term, $m_{0}$ , allowing finite baryon-masses even when the chiral condensate melts. This feature enables a unified treatment of hadronic matter across vacuum, nuclear and dense astrophysical regimes. This compact review summarizes the key structures of parity-doublet Lagrangians; outlines the mean-field formulation for nuclear and stellar matter; and highlights recent phenomenological and lattice constraints on the chirally-invariant mass. Emphasis is placed on mirror versus naïve chiral assignments; the role of vector interactions in achieving nuclear saturation; and the implications of parity doubling for the equation-of-state of dense matter and neutron-star cooling. The review concludes with current theoretical challenges and perspectives for extending these models beyond the mean-field approximation.
↳ hep-phnucl-thInt.J.Mod.Phys.A(2026)·0 citations
17
Chiral transition in a Non-Abelian Quasi-Particle Model with three quark flavours
Eleftherios P. Politis🇬🇷 · Antonis Tsapalis🇬🇷 · Fotios K. Diakonos🇬🇷
We combine the recently introduced Non-Abelian Quasi-Particle Model (NAQPM) for gluons with an ideal Fermi gas of three quark species with the aim to describe the equation of state (energy density vs. temperature) of $2 + 1$ - flavour Lattice-QCD at zero chemical potential. Allowing temperature dependent masses for the fermions, we show that above a critical temperature $T_{c}$ the quark mass has to drop rapidly in order to obtain energy density values compatible with the Lattice-QCD results. Within this framework, thus, the restoration of chiral symmetry in the system is observed. Furthermore, we demonstrate that the gluon variance -- which is a fundamental quantity of the NAQPM -- is strongly correlated to the fermion mass and decreases by orders of magnitude through the transition. The high temperature phenomenological characteristics of the gluon appear consistent to properties of the perturbative QCD gluon. The model indicates that color deconfinement and chiral symmetry restoration are interrelated and classical configurations of the QCD dynamics play an important role to the criticality of the system.
↳ hep-phhep-latnucl-thPLB(2026)·0 citations

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first authorsco-authorsvia INSPIRE