Nuclear Theory·nucl-th

Friday·May 8, 2026

12 papers—4 primary·8 cross-listed

01
Axial-vector Current and General Unpolarized Electroweak Single-nucleon Responses
T. W. Donnelly🇺🇸 · Sabine Jeschonnek🇺🇸
The present study provides an extension to our recent work on the vector (V) electromagnetic single-nucleon current and associated response functions, both for unpolarized situations and in situations where the target nucleon is polarized. Here the axial-vector (A) single-nucleon current matrix element is developed in detail and the full set of vector and axial-vector currents used to obtain the electroweak VV, AA and VA response functions. Only the unpolarized case is studied in the present work. The general forms for all of these elements are developed together with various approximation schemes in which numerical studies are provided to indicate where these approximations may be expected to be valid. The results of this work provide the basis for a deeper understanding of the roles played by the various single-nucleon form factors in weak interaction reactions on free nucleons and when using the standard ``prescription for nuclear physics'' in reactions involving nucleons in nuclei.
nucl-thPRC(2026)·0 citations
02
Relativistic mean-field study of the neutron star inner crust using the asymmetric finite difference method
Jinzhe Zhang · Hong Shen · Ying Zhang · Jinniu Hu
The ground-state properties of neutron-rich nuclear clusters in the inner crust of neutron stars are investigated within the Wigner-Seitz approximation using a relativistic mean-field framework. The radial Dirac equations are solved with an asymmetric finite-difference scheme, by which the hermiticity is preserved and spurious states are eliminated. Calculations are performed for representative Wigner-Seitz cells employing TM1-based interactions with different symmetry-energy slope parameters $L$ , as well as a parametrization with a larger nucleon effective mass. It is found that the binding energy per nucleon decreases systematically with increasing $L$ , while a larger effective mass leads to further reduction, particularly at higher densities. Quantum shell effects, which are absent in the Thomas-Fermi approximation, give rise to oscillatory density distributions and modify neutron properties. Within the Wigner-Seitz cell, the resulting neutron root-mean-square radius and chemical potential are shown to be sensitive to both $L$ and the effective nucleon mass, underscoring their important roles in determining the microscopic structure of the neutron-star inner crust.
nucl-thCPC(2026)·0 citations
03
Isomer depletion via nuclear excitation by inelastic electron scattering
Ziwen Li · Jingyan Zhao · Xuyang Pu · Yuanbin Wu
Isomer depletion via the process of nuclear excitation by inelastic electron scattering is investigated theoretically. A comprehensive study on low-energy nuclear excitations by inelastic electron scattering is performed to analyze the impact of the nuclear and ion charge, the nuclear transition energy, and the nuclear transition multipolarity on the cross section of the process. We apply the analysis to the case of isomer depletion, in which an excitation from the isomeric state to a nuclear level above the isomeric state can lead to decay to a nuclear level below the isomer itself and hence lead to the release of the energy stored in the isomer. For this purpose, the isomer depletion of $^{93m} Mo$ , $^{152m} Eu$ , and $^{178m} Hf$ , which represent the most important scenarios of isomer depletion, are studied. Our results demonstrate the capability of the process of nuclear excitation by inelastic electron scattering for isomer depletion.
nucl-thPRC(2026)·2 citations
04
Probing the density dependence of nuclear symmetry energy through isospin transport in heavy-ion reactions
S. Mallik🇮🇳 · F. Gulminelli🇫🇷 · C. Ciampi🇫🇷 · D. Gruyer🇫🇷
The density dependence of the nuclear symmetry energy remains one of the key uncertainties in contemporary nuclear physics, with significant implications for the structure of exotic nuclei, the dynamics of heavy-ion collisions, and the properties of astrophysical objects such as neutron stars and core-collapse supernovae. However, extracting robust constraints requires observables that are minimally affected by final-state interactions and are reliably predicted by transport models. This review synthesizes recent theoretical and experimental advancements in constraining the symmetry energy by leveraging isospin diffusion in heavy-ion reactions within the Fermi energy domain. Recent results from the INDRA-FAZIA collaboration, including isospin transport ratio data, and Boltzmann-Uehling-Uhlenbeck (BUU) transport model calculations are highlighted. Confidence regions for the symmetry energy are extracted from isospin transport ratios and isospin diffusion currents by utilizing state-of-the-art nuclear functionals, including both ab initio and phenomenological approaches, with a particular focus on the density regions probed by these experiments. The resulting constraints will aid future Bayesian studies of the nuclear equation of state and contribute to a more unified understanding of dense matter in both terrestrial experiments and astrophysical environments.
nucl-thhep-phnucl-exUniverse(2026)·0 citations
05
Simplified approach to extracting nucleon transversity in collinear factorization using near-side energy-energy correlators
Zhong-Bo Kang🇺🇸 · Andreas Metz🇺🇸 · Daniel Pitonyak🇺🇸 · Congyue Zhang🇺🇸
We develop a novel strategy for accessing the transversity parton distribution function (PDF) of the nucleon within collinear factorization using near-side energy-energy correlators in the dihadron fragmentation framework. We show how this removes the complications of previous approaches that must model either intrinsic parton transverse momentum or resonances in the invariant mass distribution of a final-state dihadron. We present leading-order analytical results for transverse-spin observables in semi-inclusive deep-inelastic scattering and electron-positron annihilation, highlighting their close similarity to the expressions one uses in extracting (un)polarized PDFs and (single-hadron) fragmentation functions in collinear factorization. We make predictions for kinematics relevant for existing and future facilities that demonstrate the feasibility of an energy-energy correlator program in extracting the transversity PDF.
↳ hep-phhep-exnucl-exnucl-th5 citations
06
First next-to-next-to-leading-order extraction of fragmentation functions for Lambda hyperons
Valerio Bertone🇫🇷 · Alessia Bongallino🇪🇸 · Amedeo Chiefa🇬🇧 · Miguel G. Echevarria🇪🇸 · Gunar Schnell🇪🇸
We present MAPFF1.0_Lambda, the first global analysis at next-to-next-to-leading order in perturbative QCD of the collinear unpolarised fragmentation functions of Lambda hyperons. The fit is based on data from single-inclusive electron-positron annihilation, and from both neutral-current and -- for the first time -- charged-current semi-inclusive deep-inelastic scattering. We have adopted a statistical framework based on Monte Carlo sampling and parametrised fragmentation functions in terms of a neural network. The fragmentation function set comprises a total of seven independent parton flavours, allowing for the first independent determination of valence-quark distributions. Our analysis offers new insights into the hadronisation mechanism of strange baryons and establishes a baseline for future phenomenological and experimental investigations.
↳ hep-phhep-thnucl-th0 citations
07
Squeezed spectra and back-to-back correlations of protons and antiprotons at RHIC energies
Yong Zhang🇨🇳
This study constrains the range of in-medium mass modification through a comparison of theoretical calculations with experimental transverse momentum spectra and the yield ratio {\bar{p}}/p of protons and antiprotons. Based on the constrained range and a Gaussian source model with radial ow, the theoretical predictions for the fermion back-to-back correlation (fBBC) of p{\bar{p}} pairs at RHIC energies are presented. The results reveal a strong sensitivity of the fBBC signal to the assumed source time distribution: a Lorentzian form generates a pronounced high-momentum signal, whereas an {\alpha}-stable Lévy form leads to a marked low-momentum signal. Moreover, the in-medium mass modification is shown to enhance the yield ratio {\bar{p}}/p. Therefore, events characterized by a larger {\bar{p}}/p ratio are predicted to have a significantly higher probability of exhibiting a detectable fBBC signal. This study may propose a promising new direction for the experimental observation of this phenomenon
↳ hep-phnucl-thPRC(2026)·0 citations
08
Massive hybrid stars within the extended three-flavor quark-meson diquark model
Jens O. Andersen🇳🇴 · Manuel Linares🇳🇴 · Mathias P. Nødtvedt🇳🇴
We discuss the properties of the extended three-flavor quark-meson diquark (EQMD) model as a renormalizable low-energy effective model for QCD. The effective degrees of freedom are quarks, scalar- and pseudoscalar mesons, diquarks, vector- and axial-vector mesons. We calculate the equation of state (EoS) in the mean-field approximation at $T = 0$ imposing charge neutrality for electric and color charges. We match the EoS with a low-density nuclear equation of state. We discuss how the choice of parameters in the model affects the EoS and thereby the mass-radius for hybrid stars. We show that it is possible to construct hybrid stars whose masses and radii are in agreement with recent astrophysical observations and perturbative QCD (pQCD). The addition of vector and axial vector mesons to the quark-meson diquark is essential, since it makes the EoS sufficiently stiff for intermediate densities. Our results suggest that stars with a mass larger than $M \sim 2 M_{⊙}$ have a quark core with a central density $n_{B} \geq 3.9 n_{sat}$ , where $n_{sat} \approx 0.165$ fm $^{- 3}$ is the saturation density. The speed of sound has a double-peak structure and relaxes to the conformal limit from above for large baryon chemical potentials $μ_{B}$ . This structure is caused by the decrease in the mass of the $s$ quark as $μ_{B}$ increases.
↳ hep-phastro-ph.HEnucl-thPLB(2026)·2 citations
09
A Comparative Study of Mass Extraction Schemes and $π^{\pm} - ρ^{\pm}$ Mixing
Ziyue Wang🇨🇳
We study the origin of the non-monotonic magnetic-field dependence of the lowest charged pion excitation observed in lattice QCD. In a magnetic field, the charged pion mixes with the longitudinally polarized charged rho meson, which shares the same quantum numbers. Within the SU(2) $_{f}$ Nambu--Jona-Lasinio model supplemented by a gauge invariant tree-level $π - ρ$ mixing operator constrained by the experimental $ρ^{\pm} \to π^{\pm} γ$ decay width, we compare four mass-extraction schemes: rest-mass reconstruction, local bosonization, direct determinant solving with Landau projection, and near-pole expansion. The rest-mass scheme cannot reproduce the lattice-type turnover, while in the local derivative-expansion scheme the turnover presence but is weak which occurs at large magnetic field. By contrast, the direct determinant and near-pole schemes both retain a robust non-monotonic lowest mode. The former is most faithful to the Landau-level kinematics of the charged excitation, while the latter most clearly shows that residue suppression enhances the effective mixing after canonical normalization. Our results indicate that the lattice behavior is a genuine quasiparticle mixing effect, but one whose robustness depends crucially on how the charged-meson pole structure is extracted in a magnetic field.
↳ hep-phnucl-th0 citations
10
GTMDs, orbital angular momentum, and pretzelosity
Brean Maynard🇺🇸 · Peter Schweitzer🇺🇸
The leading Generalized Transverse Momentum Dependent parton distributions (GTMDs) are studied in the bag model. The model description is shown to be theoretically consistent. The orbital angular momentum is studied in terms of the GTMD $F_{1, 4}^{q}$ and Ji sum rule. Analytical proofs of the associated sum rules are given. A deeper relationship between orbital angular momentum and the pretzelosity TMD is established in this model.
↳ hep-phnucl-th1 citation
11
Quantum spin dynamics of heavy quarks and polarization observables in relativistic heavy-ion collisions
Sunil Jaiswal🇺🇸 · Sourav Dey🇮🇳 · Amaresh Jaiswal🇮🇳
We develop a quantum spin-density-matrix framework for heavy-quark spin dynamics in relativistic heavy-ion collisions. Starting from an initial polarization induced along the magnetic-field direction, we derive the evolution equation for spin polarization within this framework and obtain analytic solutions. The evolved polarization is connected to open heavy-flavor observables via a fragmentation-based hadronization prescription. For vector mesons, the spin-alignment parameter $ρ_{00}$ is constructed by coupling the heavy-quark spin to that of the light antiquark produced during fragmentation. We confront our results with recent ALICE measurements of prompt $D^{*+}$ spin alignment in Pb--Pb collisions at $s_{NN} = 5.02 TeV$ and extract an effective depolarization strength that determines the spin-relaxation time scale. Using this fitted parameter, we provide benchmark estimates for $Λ_{c}^{+}$ and $Λ ˉ_{c}^{-}$ polarization, up to an overall spin-transfer normalization. We further estimate the recently proposed elliptic polarization harmonic arising from path-length-dependent depolarization in an anisotropic fireball.
↳ hep-phnucl-th2 citations
12
$F_{K} / F_{π}$ as a precision test of a new four flavor Domain Wall Fermion action
Renwick J. Hudspith🇺🇸 · Nicolas Garron🇬🇧 · Zack Hall🇺🇸 · Andrew Hanlon🇺🇸 · Henry Monge-Camacho🇺🇸 · Colin Morningstar🇺🇸 · Amy Nicholson🇺🇸 · Dimitra A. Pefkou🇺🇸 · Thomas R. Richardson🇺🇸 · Fernando Romero-López🇨🇭 · Miguel Salg🇨🇭 · Wyatt A. Smith🇺🇸 and 3 other authors
We present a new set of lattice QCD ensembles with four flavors of smeared Möbius Domain Wall Fermions with good chiral symmetry and small fifth-dimensional extent. A modest amount of computing resources was sufficient to generate 30 publicly-available ensembles spanning five lattice spacings and a broad range of pion masses down to physical. To scrutinize our action we determine $F_{K^{\pm}} / F_{π^{\pm}} = 1.1962 (34)$ , a key quantity for precision CKM unitarity tests, heralding a future of inexpensive high-precision calculations of hadronic observables with chiral fermions.
↳ hep-lathep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE