Nuclear Theory·nucl-th

Tuesday·January 13, 2026

12 papers—6 primary·6 cross-listed

01
Ab initio description of $p ˉ +^{3} H$ and $p ˉ +^{3} He$ systems in optical models
Pierre-Yves Duerinck🇧🇪 · Rimantas Lazauskas🇫🇷
In the context of the ongoing PUMA experiment (CERN), which investigates antiproton annihilation on atomic nuclei, we study the energy shifts and widths of Rydberg states in the $p ˉ +^{3} H$ and $p ˉ +^{3} He$ systems by performing ab initio calculations. The scattering lengths and scattering volumes are first determined by solving the Faddeev-Yakubovsky equations in configuration space. The level shifts and widths of the corresponding $p ˉ^{3} H$ and $p ˉ^{3} He$ hydrogen-like states are then obtained using the Trueman formula. A pronounced model dependence associated with the nucleon-antinucleon interaction is observed for certain states. Finally, annihilation densities are computed from the four-body wavefunctions. Comparison with the nuclear density distributions indicates that the nucleon-antinucleon annihilation is predominantly peripheral.
nucl-thPRC(2026)·3 citations
02
Entanglement study in the island of inversion region using \textit{ab initio} approach
Rohit M. Shinde · Praveen C. Srivastava
Quantum entanglement provides a unique perspective for probing nuclear structure. In this work, we employ quantum entanglement measures, including proton-neutron entanglement entropy, mutual information, and quantum relative entropy, to investigate the evolution of entanglement patterns as we approach neutron-rich nuclei. The study is carried out in the vicinity of the $N = 20$ island of inversion region consisting of even- $A$ Ne, Mg, and Si isotopes, and also for isotones corresponding to $N = 20$ . The state-of-the-art \textit{ab initio} valence space in-medium similarity renormalization group method has been used for this purpose. We have highlighted the role of proton-neutron entanglement entropy in the formation of the island of inversion region. Mutual information provides insight into the strength of correlations between proton-proton, neutron-neutron, and proton-neutron single-particle states. While these correlations are relatively weak between protons and neutrons in the ground states, they become comparable to like-particle correlations in excited states. The quantum relative entropy is also studied between $0^{+}$ and $2^{+}$ states of the Ne, Mg, and Si isotopes, as well as $N = 20$ isotones, using the Kullback-Leibler divergence and Jensen-Shannon divergence. We have performed these calculations by expressing the nuclear wavefunctions in a Slater-determinant basis and analyzing them through complementary partitions, including proton-neutron and mode-resolved factorizations.
nucl-thnucl-exPRC(2026)·3 citations
03
Unfolding of exotic near-threshold structure and decay dynamics in $^{17}$ B
A. Volya🇺🇸 · S. M. Wang🇨🇳 · M. Płoszajczak🇫🇷 · Z. C. Xu🇨🇳
Neutron-rich boron isotopes provide a valuable testing ground for threshold-driven structure and reaction phenomena, including halo formation and exotic decay modes. In particular, the structure of $^{17} B$ and its relation to unbound $^{16} B$ are of special interest. The $^{16} B$ nucleus is slightly unbound by approximately $50 keV$ , while $^{17} B$ is bound with a neutron separation energy of about $1.4 - 1.6 MeV$ . The observation of a $1640 keV$ $γ$ ray in $^{17} B$ , which we argue originates from a $1/ 2^{-}$ excited state, points to a remarkable situation in which $γ$ decay and two-neutron decay can compete. We analyze and identify the main reasons for this competition: $L = 2$ emission of the neutron pair, and structural realignment driven by the proximity of the one-body threshold, in particular the nearby $s$ -wave neutron decay channel. The decay is a unique near-threshold $L = 2$ process in which multiple structural components contribute, each with coexisting direct and virtual sequential amplitudes whose interference governs the observables. Because threshold dynamics, continuum coupling, and interference of multiple quantum pathways are universal, closely related scenarios arise in ultracold atoms near Feshbach resonances, few-body atomic and molecular breakups, mesoscopic and photonic open systems, and other areas where open-quantum-system effects impact observables. We employ advanced theoretical models to study this first-of-its-kind case and provide a coherent theoretical perspective based on configuration interaction and complex-energy formalisms that incorporate both reaction continuum and structural effects near threshold.
nucl-thPRResearch(2026)·0 citations
04
Physics-Informed Neural Network for Solving the Heavy Quark Diffusion in the Expanding QCD Medium
Wenhua Fan🇨🇳 · Jiamin Liu🇨🇳 · Huansang Yang🇺🇸 · Baoyi Chen🇨🇳
We employ Physics-Informed Neural Networks (PINNs) to investigate the dynamical evolution of heavy quarks within the expanding hot QCD medium generated in relativistic heavy-ion collisions. The heavy quark dynamics are first modeled under the assumption of complete kinetic thermalization, followed by a more realistic study of non-thermal diffusion governed by the Fokker-Planck (FP) equation. In both scenarios, the background evolution of the hot QCD medium is encoded into the coefficients of the diffusion equations. These equations are solved within the PINN framework, where the initial conditions, physical constraints from the dynamical equation, and probability conservation are incorporated into the loss function.We also compare the performance of the FP-PINN with a supervised five-dimensional DNN trained on labeled data generated from Langevin-based reference distributions.This work provides a valuable reference for applying PINN-based models to particle diffusion in phase space, laying the foundation for future studies of heavy quarkonium production via realistic non-thermal heavy-quark coalescence.
nucl-thPRC(2026)·0 citations
05
Multi-Physics Bayesian Analysis of Neutron Star Crust Using Relativistic Mean-Field Model
Vishal Parmar🇮🇹 · Ignazio Bombaci🇮🇹
We study the properties of neutron-star crust within a Bayesian framework based on a unified relativistic mean-field (RMF) description of dense matter. The analysis focuses on the posterior distributions of crust properties, constrained by nuclear experimental data, chiral effective field theory, and multimessenger neutron-star observations. In the inference, the outer crust is fixed using the AME2020 nuclear mass table, supplemented by Hartree--Fock--Bogoliubov mass models, while the inner crust is described using a compressible liquid-drop model consistently coupled to the RMF interaction. The same RMF framework is used to describe the uniform core, ensuring a unified treatment across all density regimes. From the resulting posteriors, we extract key crustal observables, including the crust--core transition density and pressure, crust thickness, crust mass, and the fractional crustal moment of inertia. We find that the transition density is primarily governed by the symmetry-energy slope $L$ and curvature $K_{sym}$ evaluated at sub-saturation densities, while the transition pressure plays a central role in determining global crustal properties. The inner-crust equation of state reflects a collective interplay between isovector nuclear-matter properties rather than a dependence on any single parameter. We also assess the impact of using matched crust--core constructions and show that they can introduce systematic differences in predicted neutron-star properties when compared with fully unified treatments.
nucl-thastro-ph.SRPRD(2026)·3 citations
06
Learning the relations between neutron star and nuclear matter properties with symbolic regression
N. K. Patra · Tuhin Malik · Kai Zhou · Constança Providência
The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies. In our analysis, we apply a machine learning algorithm known as symbolic regression, paired with principal component analysis, to datasets generated from Bayesian inference over relativistic mean-field models. A systematic Principal Component Analysis has allowed to break down the percentage contribution of each element or feature in the relationships obtained. This study examines two main models (datasets): the NL model, which includes nucleonic degrees of freedom; and the NL-hyp model, which includes hyperons in addition to nucleons. Our analysis confirms a robust correlation between the tidal deformability of a 1.4 $M_\odot$ neutron star and $β$ -equilibrium pressure at twice the nuclear saturation density. This correlation remains once hyperons are included. The contribution of the different nuclear matter properties at saturation to the radius and tidal deformability was calculated. It was shown that the isovector properties have the largest impact, with a contribution of about 90\%. We also studied the relationship between the proton fraction at different densities and various symmetry energy parameters defined at saturation density. For the hyperon data set, we took into account the effects of the negatively charged hyperon $Ξ$ in order to recover the relationships. Our study reveals the individual impact of various symmetry energy parameters on proton fractions at different densities.
nucl-thastro-ph.SRgr-qchep-ph+10 citations
07
Direct transfer to $^{46, 48}$ K as a survey of the $π (s_{1/2})$ $- ν (s d p f)$ interaction
C. J. Paxman🇬🇧 · A. Matta🇫🇷 · W. N. Catford🇬🇧 · G. Lotay🇬🇧 · M. Assié🇫🇷 · E. Clément🇫🇷 · A. Lemasson🇫🇷 · D. Ramos🇫🇷 · N. A. Orr🇫🇷 · F. Galtarossa🇫🇷 · V. Girard-Alcindor🇫🇷 · J. Dudouet🇫🇷 and 67 other authors
The collapse of the canonical $N = 28$ magic number in nuclei with $Z < 20$ has drawn significant interest as it relates to the emergence of an island of inversion centered on $^{42}$ Si and $^{44}$ S. In particular, interactions between the $π s_{1/2}$ orbital -- empty in $^{42}$ Si and full in $^{44}$ S -- and the neutron orbitals just above and below the $N = 28$ gap are expected to be critical in this region, but remain relatively unexplored. In this paper, we expand upon the results of our previous study of the direct transfer reaction $^{47}$ K(d,p $γ$ ) $^{48}$ K [C.\,J.~Paxman \textit{et al.}, Phys. Rev. Lett. 134, 162504 (2025)] with the results of the complementary $^{47}$ K(d,t $γ$ ) $^{46}$ K reaction. Through this study, we present a comprehensive scan of the interaction between the critical $π s_{1/2}$ orbital and a broad range of neutron orbitals spanning nearly two full shells. We identify several discrepancies between the experimental results and state-of-the-art shell model calculations, which suggest a deficiency of the shell model to fully capture the complex proton configuration mixing in this region, highlighting a significant challenge for single-particle descriptions of the island of inversion.
↳ nucl-exnucl-th0 citations
08
Hadronic Probes of Non-Standard Neutrino Interactions
Carlos Henrique de Lima🇨🇦 · David McKeen🇨🇦 · John Ng🇨🇦 · Douglas Tuckler🇨🇦
In this work, we study leptonic decays of hadrons as probes of light neutrinophilic scalars that mediate enhanced neutrino self-interactions. Such scalars can be emitted in processes involving neutrinos, turning two-body decays into three-body final states and producing characteristic spectral distortions. We compute these effects for charged pion decay and nuclear electron capture decay, including both on-shell and off-shell scalar emission, as well as the loop-induced renormalization required to cancel divergences. Using these results, we derive the projected sensitivity of PIONEER and assess the current and future reach of BeEST. The resulting low-energy spectral tails provide a characteristic signal for light neutrinophilic scalars, making upcoming hadron decay experiments powerful probes of light mediators of non-standard neutrino self-interactions.
↳ hep-phhep-exnucl-thPRD(2026)·2 citations
09
Lattice QCD determination of the $γ Z$ box contribution to the proton weak charge
Zhao-long Zhang🇨🇳 · Xu Feng🇨🇳 · Mikhail Gorchtein🇩🇪 · Lu-Chang Jin🇺🇸 · Chuan Liu🇨🇳 · Chien-Yeah Seng🇺🇸
We present the first lattice QCD determination of the $γ Z$ box contribution to parity-violating electron-proton scattering, $□_{γ Z}$ , a key ingredient for the precise tests of the Standard Model via the proton weak charge. Our calculation covers the electron beam energies up to $E = 155 M e V$ . For the axial-vector component, we achieve reduced uncertainties across the entire energy range compared with phenomenological estimates. For the vector component, the uncertainties remain slightly larger after continuum extrapolation. At $E = 0$ , where the vector part vanishes, we obtain $□_{γ Z} = 0.00412 (9)$ , reducing the uncertainty by a factor of $2$ relative to the most precise previous determination. Incorporating this result yields an updated weak charge of $Q_{W}^{p} = 0.06987 (50)$ . The calculated energy dependence of $□_{γ Z}$ further provides a first-principles input for the upcoming P2 experiment at Mainz, which will operate at the optimized beam energy of $155 M e V$ to extract $Q_{W}^{p}$ .
↳ hep-lathep-phnucl-th3 citations
10
Probing the microscopic origin of prompt and non-prompt $D^{0}$ production through event-shape engineering in proton-proton collisions at the LHC
Aswathy Menon Kavumpadikkal Radhakrishnan · Suraj Prasad · Purnima Srivastava · Raghunath Sahoo
Heavy-flavour hadrons are produced in the early stages of ultra-relativistic collisions at the LHC via hard partonic interactions and experience the whole system evolution. The study of prompt and non-prompt $D^{0}$ mesons provides an independent avenue to test the theories of quantum chromodynamics and to investigate beauty hadron production. Moreover, the production of both prompt and non-prompt $D^{0}$ is influenced by microscopic processes such as multi-partonic interactions (MPI) and hadronisation through fragmentation. In this study, an attempt is made to understand the production of prompt and non-prompt $D^{0}$ mesons in proton-proton collisions at $s = 13.6$ TeV using the PYTHIA8 event generator, which offers a qualitative description of charm production. The role of the transverse momentum transfer in the hardest partonic scattering ( $p^_{T}$ ), MPI, and color reconnection is systematically explored. In addition, the charged particle production in different topological regions with respect to the leading $D^{0}$ meson is studied to assess the influence of the $D^{0}$ meson on the event topology and to examine the selection biases arising from the use of charged particle multiplicity as an event classifier.
↳ hep-phhep-exnucl-exnucl-th0 citations
11
EPOS4 Model Predictions for Global Observables in Pb-Pb Collisions at $s_{N N}$ = 5.36 TeV
Hirak Kumar Koley🇮🇳 · Subikash Choudhury🇮🇳 · Mitali Mondal🇮🇳
The study of the Quark-Gluon Plasma (QGP), a deconfined state of nuclear matter, remains a central focus of high-energy heavy-ion collision experiments. The recent operation of the Large Hadron Collider (LHC) in Run 3 at the new center-of-mass energy of $s_{N N} = 5.36$ TeV necessitates theoretical predictions to characterize the energy dependence and bulk properties of the medium. In this study, we present comprehensive EPOS4 model predictions for key global observables in Pb-Pb collisions at $5.36$ TeV. We focus on the centrality dependence of the charged-particle pseudorapidity density ( $d N_{c h} / d η$ ), integrated yields ( $d N / d y$ ), mean transverse momentum ( $⟨ p_{T} ⟩$ ) for light-flavor hadrons ( $π^{\pm}, K^{\pm}, p (p ˉ)$ ), and the charged particle nuclear modification factor ( $R_{AA}$ ). The EPOS4 framework successfully captures the strong mass-dependent rise of $⟨ p_{T} ⟩$ with multiplicity, a definitive signature of collective radial flow. Furthermore, the predicted charged hadron $R_{AA}$ demonstrates a clear suppression, consistent with energy loss mechanisms incorporated into the model. By comparing these predictions to existing $5.02$ TeV data, we demonstrate that the EPOS4 model offers a consistent and robust description of heavy-ion dynamics, projecting minimal energy evolution for these bulk and hard-probe observables between the two energies.
↳ hep-phhep-exnucl-thPoS(2026)·1 citation
12
Dynamical gluon effects in twist-3 generalized parton distributions of the proton
Ziqi Zhang🇨🇳 · Chandan Mondal🇨🇳 · Siqi Xu🇨🇳 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸
Within the Basis Light-Front Quantization framework, we systematically investigate the subleading-twist (twist-3) generalized parton distributions (GPDs) of the proton's valence quarks beyond the Wandzura--Wilczek (WW) approximation. The twist-3 GPDs are not independent; through the equations of motion they decompose into a non-genuine contribution and a genuine twist-3 term. The latter encodes quark--quark--gluon correlations and involves interference between the light-front Fock sectors |qqq> and |qqqg>, which are typically neglected in the WW approximation. Using light-front wave functions obtained from diagonalizing the proton light-front Hamiltonian for its |qqq> and |qqqg> Fock components, we compute these GPDs via their overlap representations. To further explore their physical implications, we also evaluate several twist-3--related quantities, including the quark orbital angular momentum, the total quark spin contribution, and the quark spin--orbit correlation. Our results provide new nonperturbative input on higher-twist dynamics particularly multi-parton interference effects relevant for future measurements at the EicC and the EIC.
↳ hep-phnucl-thPRD(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE