Nuclear Theory·nucl-th

Monday·August 4, 2025

12 papers—5 primary·7 cross-listed

01
Exploring Shell Evolution and N = 40 Magicity in Light-Mass Nuclei with Relativistc Mean Field Approach
Priyanka Saini · Praveen K. Yadav · M. S. Mehta · M. Bhuyan
We employ the relativistic mean-field (RMF) approach with NL3 parameters to study shell and sub-shell closures in the isotopic chains of Cl, Ar, K, Ca, Sc, Ti, V, and Cr nuclei. By analyzing nuclear bulk properties, binding energy, charge radii, two-neutron separation energies, deformation parameters ( $β_{2}$ ), and single-particle levels we trace the evolution of magic numbers. Our results highlight the single-particle energy levels to examine nuclear shell closure and the occupancy of individual nucleon orbitals. A comprehensive picture of N = 34 shell closure is particularly prominent in the isotopic chains of Cl, Ar, and Ti nuclei, where the magicity associated with this number remains evident across several isotopes. In contrast, the N = 40 exhibits a more robust and widespread manifestation across all the examined nuclei, indicating that its shell closure is less sensitive to the specific isotopic environment and more universally applicable across the given nuclear systems. To further validate these closures, we apply the coherent density fluctuation model (CDFM) to assess isospin-dependent observables, such as the symmetry energy and its surface and volume components. A systematic analysis of the symmetry energy, computed using the relativistic mean-field (RMF) approach, maps the evolution of the shell structure at $N = 20$ and 28, supports sub-magicity at $N = 34$ , and strongly suggests a shell closure at $N = 40$ , reflected consistently in both bulk and surface properties. The interplay between shell structure and nuclear deformation remains a central topic of research, and future theoretical and experimental studies will continue to shed light on the complex behaviour of these fascinating systems.
nucl-th0 citations
02
Implication of neutron star observations to the origin of nucleon mass
Bikai Gao🇯🇵 · Xiang Liu🇯🇵 · Masayasu Harada🇯🇵 · Yong-Liang Ma🇨🇳
We investigate the implications of neutron star observations for understanding the origin of nucleon mass using a framework that combines three complementary approaches: the equation of state based on parity doublet structure for hadronic matter below $2 n_{0}$ , the Nambu-Jona-Lasinio (NJL) model for quark matter above $5 n_{0}$ , and a model-independent analysis of the intermediate density region based on fundamental physical principles. By systematically exploring parameter spaces and comparing theoretical predictions with recent observational constraints, we establish constraints on the chiral invariant mass. Our results suggest that more than a half of the nucleon mass originates from sources beyond spontaneous chiral symmetry breaking, challenging conventional understanding of nucleon mass generation. These constraints arise solely from fundamental physical principles and observational data, independent of specific assumptions about the nature of the quark-hadron transition, providing robust insights into the microscopic origin of hadron masses.
nucl-thastro-ph.HEastro-ph.SRhep-ph+1SCPMA(2026)·9 citations
03
Nonlocal {\it in-medium} effective interaction for nucleon scattering off isospin-asymmetric targets
J. I. Fuentealba-Bustamante · H.F. Arellano
We have investigated the role of isospin asymmetry of the $N N$ effective interaction in the context of $N A$ elastic scattering. To this purpose we represent the {\it in-medium} $g$ matrix as an admixture of isospin-symmetric nuclear matter and pure neutron matter solutions of Brueckner-Hartree-Fock equations for infinite nuclear matter, denoted as $g [ρ, β]$ . We use the Argonne $v_{18}$ bare potential to represent the $N N$ interaction in free space, due to its ability to describe the $N N$ scattering amplitudes up to 350 MeV. The density-dependent isospin-asymmetric $g$ matrices are then used to calculate optical model potentials for elastic nucleon scattering off closed-shell nuclei. For this aim, we make use of the Arellano-Bauge $δ g$ -folding approach suited for an explicit treatment of nonlocal density matrices. This approach allows to account for the local isospin-asymmetry and density dependence of the {\it in-medium} $N N$ interaction. The resulting optical potentials are nonlocal since the entire nonlocal structure of the $g$ matrix is retained. We observe that including the isospin asymmetry in the $g$ matrix allows for a reasonable description of differential cross-sections at nucleon beam energies between 40 and 200 MeV. In the case of proton scattering at energies below $\sim$ 65 MeV, at momentum transfers $q$ below $\sim$ 1 fm $^{- 1}$ , the inclusion of neutronic-matter $g$ matrices yields better agreement with the data as compared to the case when symmetric nuclear matter $g$ matrices are used. These results provide evidence that the isospin-asymmetry in the $N N$ effective interaction yield non-negligible effects in nucleon scattering off isospin-asymmetric targets at beam energies below 65 MeV.
nucl-thPRC(2025)·1 citation
04
Harmonic chiral vibration in triaxial nuclei
R. Budaca · A. I. Budaca
The low spin states of chiral partner bands are described by means of harmonic oscillations of the total angular momentum vector. The validity of the adopted approximation is established in terms of triaxiality, quasiparticle alignments and the maximal total angular momentum. The spectral properties of the model are described in detail with experimental realizations presented for nuclei with large resultant quasiparticle alignments. The model provides a simple phenomenological way for the determination of the triaxial deformation from the experimental data and easily discernable observable signatures.
nucl-thPLB(2025)·1 citation
05
Coupled-channel contributions to the GDH sum rule from the Jülich-Bonn approach
Carolin Schneider🇩🇪 · Deborah Rönchen🇩🇪 · Christoph Hanhart🇩🇪 · Ulf-G. Meißner🇩🇪
We study the Gerasimov-Drell-Hearn (GDH) sum rule within a dynamical coupled-channel approach, the Jülich-Bonn model for light baryon resonances based on fits to an extensive data base of pion and photon induced data. Recently published photoproduction data for different observables with $π N$ and $η N$ final states are analyzed simultaneously with older data for the reactions $π N \to π N$ , $η N$ , $K Λ$ , $K Σ$ and $γ p \to π N$ , $η N$ , $K Λ$ , $K Σ$ . The impact of the new data on the resonance spectrum is investigated and the contribution of the individual channels to the GDH integral is determined.
nucl-thhep-phnucl-exEPJA(2025)·2 citations
06
Pionic gluons from global QCD analysis of experimental and lattice data
William Good🇺🇸 · Patrick C. Barry🇺🇸 · Huey-Wen Lin🇺🇸 · W. Melnitchouk🇺🇸 · Alex NieMiera🇺🇸 · Nobuo Sato🇺🇸
We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, with lattice-QCD data on gluonic pseudo--Ioffe-time distributions fitted simultaneously with experimental Drell-Yan and leading neutron electroproduction data. Inclusion of the lattice results with parametrized systematic corrections significantly reduces the uncertainties on the gluon PDF at parton momentum fractions $x ≳ 0.2$ , revealing a higher gluon density in the pion at large $x$ than in the proton. The similar gluon momentum fractions in the pion and proton further suggests a relative suppression of the pion gluon density at small $x$ .
↳ hep-phhep-exhep-latnucl-th7 citations
07
Truncation uncertainties for accurate quantum simulations of lattice gauge theories
Anthony N. Ciavarella🇺🇸 · Siddharth Hariprakash🇺🇸 · Jad C. Halimeh🇩🇪 · Christian W. Bauer🇺🇸
The encoding of lattice gauge theories onto quantum computers requires a discretization of the gauge field's Hilbert space on each link, which presents errors with respect to the Kogut--Susskind limit. In the electric basis, Hilbert space fragmentation has recently been shown to limit the excitation of large electric fields. Here, we leverage this to develop a formalism for estimating the size of truncation errors in the electric basis. Generically, the truncation error falls off as a factorial of the field truncation. Examples of this formalism are applied to the Schwinger model and a pure U(1) lattice gauge theory. For reasonable choices of parameters, we improve on previous error estimates by a factor of 10^{306}.
↳ quant-phhep-lathep-phnucl-th20 citations
08
Variational Neural Network Approach to QFT in the Field Basis
Kevin Braga🇺🇸 · Nobuo Sato🇺🇸 · Adam P. Szczepaniak🇺🇸
We present a variational neural network approach for solving quantum field theories in the field basis, focusing on the free Klein-Gordon model formulated in momentum space. While recent studies have explored neural-network-based variational methods for scalar field theory in position space, a systematic benchmark of the analytically solvable Klein-Gordon ground state -- particularly in the momentum-space field basis -- has been lacking. In this work, we represent the ground-state wavefunctional as a neural network defined on a discretized set of field configurations and train it by minimizing the Hamiltonian expectation value. This framework enables direct comparison to exact analytic results for a range of key observables, including the ground-state energy, two-point correlators, expectation value of the field, and the structure of the learned wavefunctional itself. Our results provide quantitative diagnostics of accuracy and demonstrate the suitability of momentum space for benchmarking neural network approaches, while establishing a foundation for future extensions to interacting models and position-space formulations.
↳ hep-phnucl-thPLB(2026)·1 citation
09
Analytic Solution for the Helicity Evolution Equations at Small $x$ and Large $N_{c} & N_{f}$
Jeremy Borden🇺🇸 · Yuri V. Kovchegov🇺🇸
We construct an exact analytic solution of the revised small- $x$ helicity evolution equations, where the contributions of the quark-to-gluon and gluon-to-quark transition operators were newly included. These evolution equations are written in the large- $N_{c} & N_{f}$ limit and are double-logarithmic, resumming powers of $α_{s} ln^{2} (1/ x)$ . Here $N_{c}$ and $N_{f}$ are the numbers of quark colors and flavors, while $α_{s}$ is the strong coupling constant and $x$ is the Bjorken- $x$ variable. Using our solution, we obtain analytic expressions for the flavor singlet quark and gluon helicity parton distribution functions (PDFs) and for the $g_{1}$ structure function as double-inverse Laplace transforms. We also extract analytic expressions for the four DGLAP polarized anomalous dimensions $Δ γ_{q q}, Δ γ_{q G}, Δ γ_{Gq}$ , and $Δ γ_{GG}$ : these expressions resum powers of $α_{s} / ω^{2}$ to all orders at large- $N_{c} & N_{f}$ (with $ω$ the Mellin moment variable). We extract the leading small- $x$ growth of the helicity distributions, \begin{align} \Delta\Sigma(x,Q^2) \sim \Delta G(x,Q^2)\sim g_1(x,Q^2) \sim \left(\frac{1}{x}\right)^{\alpha_h}, \end{align} where the intercept $α_{h}$ satisfies an algebraic equation. We determine $α_{h}$ numerically for various values of $N_{c}$ and $N_{f}$ . We further obtain the explicit asymptotic expressions for the helicity distributions, which yield numerical values for the ratio of the gluon helicity PDF to the flavor singlet quark helicity PDF in the small- $x$ asymptotic limit (for different $N_{f} / N_{c}$ ). We find that all our predictions for polarized DGLAP anomalous dimensions are fully consistent with the existing finite-order calculations. Similar to the large- $N_{c}$ case, our intercept $α_{h}$ exhibits a very slight disagreement with the predictions made within the infrared evolution equations framework.
↳ hep-phnucl-thPRD(2026)·12 citations
10
Thermoelectric figure of merit and the deconfinement phase transition
Kamaljeet Singh🇮🇳 · Raghunath Sahoo🇮🇳
Thermoelectric phenomena are traditionally associated with the interconversion of thermal and electrical energy in many-body systems. In the context of high-temperature quantum chromodynamics (QCD) matter produced in relativistic heavy-ion collisions, thermoelectric responses can provide insight into the evolving microscopic dynamics and the redistribution of effective degrees of freedom across the phase transition region. In this work, for the first time, we present a phenomenological study of the thermoelectric figure of merit ($ ZT $) in hot QCD matter, with a particular focus on its behavior across the hadronic and quark-gluon plasma phases. Using model-based calculations for the electrical conductivity, Seebeck coefficient, and thermal conductivity, we analyze the temperature dependence of $ ZT $ and identify characteristic features near the QCD phase transition temperature. Our results indicate that $ ZT $ exhibits nontrivial behavior near the transition region, reflecting the changing transport properties and active degrees of freedom in the medium. This phenomenological study of the thermoelectric figure of merit provides a complementary perspective to traditional transport studies and may provide critical insights for advancing the understanding of QCD matter through the transition region.
↳ hep-phhep-exhep-thnucl-ex+1PLB(2026)·2 citations
11
$ψ (2 S)$ production in jets using NRQCD
Marston Copeland🇺🇸 · Lin Dai🇨🇳 · Yu Fu🇺🇸 · Jyotirmoy Roy🇺🇸
Based on recent data from LHCb, we study $ψ (2 S)$ production in jets using non-relativistic QCD (NRQCD) in conjunction with the Fragmenting Jet Function (FJF) and Gluon Fragmentation Improved Pythia (GFIP) formalisms. Similar to previous studies of $J / ψ$ production in jets, our results show that these formalisms offer a much better description of data than the default Pythia+NRQCD prediction. We compare and contrast the predictions from the FJF formalism and the GFIP approach. In addition, our results show that the distribution of $ψ (2 S)$ in jets is an excellent discriminator to test different predictions for the $ψ (2 S)$ LDMEs from various extractions. We find a large disparity between the predictions from three different collaborations, showing that a more precise extraction of the $ψ (2 S)$ LDMEs may be necessary.
↳ hep-phnucl-thJHEP(2026)·10 citations
12
String-based axial and helicity-flip GPDs: a comparison to lattice QCD
Florian Hechenberger🇺🇸 · Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We construct an analytic, string based representation of the nucleon's axial and helicity flip conformal moments of generalized parton distributions that holds for any skewness and for both the quark and gluon channels. The starting point is the Mellin Barnes resummation of the conformal partial wave expansion, where the moments are parametrized by open (Reggeon) and closed string (Pomeron) trajectories with slopes determined by experimental form factors and meson/glueball spectroscopy. The forward limits are fixed by the empirical unpolarized and polarized parton distributions. Polynomiality, crossing symmetry and support are satisfied by construction. After NLO DGLAP ERBL evolution to $μ = 2$ GeV our analytic framework (i) reproduces some of the currently available lattice moments of $E$ and $H$ in the non singlet sector, (ii) predicts sea quark and gluon polarized moments that will be testable by forthcoming simulations and experiments at Jefferson Lab and the future EIC, and (iii) yields axial and helicity flip GPDs in $x$ space in reasonable agreement with lattice QCD.
↳ hep-phnucl-thPRD(2025)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE