Nuclear Theory·nucl-th

Monday·May 4, 2026

11 papers—4 primary·7 cross-listed

01
[Submitted on 1 May 2026]
$ρ$ mesons in finite magnetic field and finite temperature
Zhiyang Liu🇨🇳 · Min Zhou🇨🇳 · Yvming Tian🇨🇳 · Rui Zhou🇨🇳 · Guoyun Shao🇨🇳 · Shijun Mao🇨🇳
The mass spectra of $ρ$ mesons ( $ρ_{Q = \pm 1}^{s_{z} = 0, \pm 1}$ and $ρ_{Q = 0}^{s_{z} = 0, \pm 1}$ ) at finite magnetic field and temperature are studied in frame of the two-flavor Nambu-Jona-Lasinio model. Fully considering the breaking of translational invariance induced by external magnetic field, the analytical form of $ρ$ meson propagators have been derived in the Ritus scheme and Schwinger scheme, which gives the same algebraic formula. When solving the pole equation of $ρ$ meson propagators, multiple solutions of the meson mass appear due to the dimension reduction of their constituent quarks in magnetic fields. At vanishing temperature, we focus on the $ρ$ meson masses $M_{ρ}$ corresponding to the lowest value solution of the pole equation. $M_{ρ_{+}^{-}}$ , $M_{ρ_{+}^{0}}$ and $M_{ρ_{0}^{\pm}}$ increase with magnetic field. $M_{ρ_{+}^{+}}$ firstly decreases and then becomes saturated with increasing magnetic field. $M_{ρ_{0}^{0}}$ is not sensitive to magnetic field. These results are consistent with the available LQCD simulations. At finite temperature, we discuss the lowest four/five solutions of $ρ$ meson masses $M_{ρ}^{i = 0, 1, 2, 3, 4}$ . With fixed magnetic field, they decrease with temperature, and approach the mass sum of their constituent quarks at high temperature. The mass solution $M_{ρ}^{i}$ for different mesons $ρ_{+}^{0, \pm}$ and $ρ_{0}^{0, \pm}$ may become degenerate at finite magnetic field and temperature.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2605.00561 [pdf]
3 citations
02
[Submitted on 1 May 2026]
Comparative Study of Langevin and Random Walk Models for Nuclear Fission in the Overdamped Regime
A. Augustyn · T. Cap · M. Kowal · K. Pomorski
We present a comparative study of Langevin dynamics and a Metropolis random walk model applied to thermal neutron-induced fission of $^{229}$ Th, $^{235}$ U, $^{239}$ Pu, $^{245}$ Cm, $^{249}$ Cf, and $^{255}$ Fm. Both methods are implemented within an identical four-dimensional Fourier-over-Spheroid framework, using potential energy surfaces derived from the macroscopic-microscopic model. We show that the Metropolis walk corresponds to the overdamped limit of the Langevin equations and confirm this correspondence numerically by Langevin calculations performed in the strongly damped regime and with quantum corrections to the random force switched off. Under these conditions, the two approaches produce essentially identical mass distributions for the lighter actinides. Systematic deviations develop for the heavier actinides, where the Langevin dynamics yields a non-negligible symmetric fission component absent in the random walk results. We trace this difference to the kinematic structure of the Metropolis sampling and to the residual inertial dynamics retained in the Langevin framework. A parallel comparison of Langevin calculations with and without the quantum-corrected effective temperature $T^{*}$ isolates the contribution of zero-point fluctuations and suggests that their standard phenomenological treatment may overestimate their impact in certain cases. Both approaches qualitatively reproduce the asymmetric peak positions and their systematic evolution across the actinide chain, while a common quantitative limitation -- the narrowness of the predicted distributions -- points to the role of higher-dimensional deformation modes not included in the present parametrization.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.00586 [pdf]
0 citations
03
[Submitted on 1 May 2026]
Hyperon-nucleon interaction through the $K^{-} d \to π Λ N$ reaction
Shunsuke Yasunaga🇯🇵 · Daisuke Jido🇯🇵
The hyperon-nucleon interaction is investigated through the final-state interaction in the $K^{-} d \to π^{-} Λ p$ reaction. We focus on the $Λ N$ - $Σ N$ coupled-channel interaction, which produces characteristic structures around the $Σ N$ thresholds in the $Λ p$ invariant mass spectrum. The spin-triplet $Σ N \to Λ p$ conversion amplitude is constructed within the $K$ -matrix formalism using scattering lengths in the isospin basis. We first examine the dependence of the conversion amplitude on the $Σ N$ scattering lengths and find that the threshold structure is particularly sensitive to the sign of the real part of the $I = 1/2$ scattering length. We then calculate the $Λ p$ invariant mass spectrum of the $K^{-} d \to π^{-} Λ p$ reaction, including the contributions from the background diagrams. The resulting spectra show characteristic structures around the $Σ N$ thresholds, whose shapes depend on the choice of the interaction parameters. These results suggest that the $Λ p$ invariant mass spectrum can serve as a useful observable for constraining the $Λ N$ - $Σ N$ coupled-channel interaction.
Comments:
4 pages, 3 figures, Proceedings of the 2025 International Conference on the Structure of Baryons (Baryons 2025), 10-14 Nov. 2025, Jeju, South Korea
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.00727 [pdf]
J.Subatomic Part.Cosmol.(2026)·0 citations
04
[Submitted on 1 May 2026]
Two-body current and axial form factor effects in charged-current quasielastic neutrino-nucleus scattering within the NEUT event generator
T. Franco-Munoz🇧🇪 · J. McKean🇯🇵 · J. García-Marcos🇧🇪 · M. Hooft🇧🇪 · R. González-Jiménez🇪🇸 · N. Jachowicz🇧🇪 · J. M. Udías🇪🇸
We present a charged-current quasielastic neutrino-nucleus scattering model based on an unfactorized representation of the spectral function, employing relativistic momentum distributions for bound nucleons and the relativistic distorted-wave impulse approximation with an energy-dependent relativistic potential to describe the scattered nucleon. The model incorporates two-body meson-exchange currents contributing to one-particle-one-hole final states and tests several axial form factor parametrizations, including recent LQCD and MINERvA fits. It is implemented in the NEUT event generator and benchmarked against T2K and MINERvA $ν_{μ}$ - $^{12}$ C CC0 $π$ measurements. We find that two-body meson-exchange currents lead to a sizeable increase of the total cross section, arising from an enhancement of the transverse response, which is the dominant component in charged-current neutrino scattering. On the other hand, recent fits of the axial form factor predict larger values than the standard dipole form, yielding a systematic enhancement of the cross section. The LQCD+MINERvA parametrization tends to overestimate the data, while the MINERvA-only fit provides a more moderate increase. Overall, no single configuration consistently provides the best agreement with the different datasets.
Comments:
18 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2605.00756 [pdf]
PRD(2026)·3 citations
05
[Submitted on 30 Apr 2026] (cross-list from hep-ph)
Baryonic Bound States in the Non-Local NJL Model
Arpan Chatterjee · Stefan Groote
Baryons, as three-quark bound states, require a covariant treatment in the intermediate-energy regime where perturbative QCD is no longer applicable and where nonperturbative correlations dominate. This article reformulates the content of the CERN Baltic Conference 2025 presentation on baryonic bound states in the non-local Nambu--Jona-Lasinio (NJL) model. We review how the relativistic Faddeev approach reduces the three-body quark problem to an effective quark--diquark bound-state problem, describe the scalar and axial-vector diquark channels, and show how the resulting quark--diquark Bethe--Salpeter equation can be written as an eigenvalue problem for the baryon mass. The non-local NJL framework, motivated by QCD-based nonlocal interactions and Dyson--Schwinger considerations, provides a compact description in which baryon masses and form factors are extracted from the numerical solution of coupled integral equations.
Comments:
6 pages, 2 figures, talk presented by Arpan Chatterjee at the 5th CERN Baltic Conference (CBC 2025), Kaunas University of Technology, Kaunas, Lithuania, 14--16 October 2025
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2605.00084 [pdf]
0 citations
06
[Submitted on 1 May 2026] (cross-list from hep-ph)
Evidence for Quark Confinement in the Proton
Xiangdong Ji🇨🇳 · Gerald A. Miller🇺🇸 · Chen Yang🇺🇸
The strong interaction is the fundamental force that holds quarks and the gluon force carriers together to form protons and neutrons and also binds the atomic nucleus. The theory governing quark-gluon interactions is Quantum Chromodynamics (QCD). A wide variety of experimental data teaches us that quarks and gluons cannot be observed in isolation, a phenomenon known as confinement that is unique to QCD. But no one has used QCD to mathematically prove confinement. Here we show how to define and measure the force on quarks in the proton using available experimental data. Direct evidence for confinement is obtained because the force is found to be attractive and constant for a wide range of quark positions. This work guides future experimental efforts at future Electron-Ion Colliders aimed at obtaining a rigorous quantitative understanding of confinement and the origin of nuclear mass.
Comments:
20 pages, 2 figures. Includes 6 pages of Supplementary Materials
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2605.00339 [pdf]
Research(2026)·4 citations
07
[Submitted on 1 May 2026] (cross-list from hep-ph)
Twist-2 relations for the twist-3 tensor-polarized distribution function $f_{L T}$ of a spin-1 hadron by the operator-product-expansion method
S. Kumano🇨🇳 · Kenshi Kuroki🇨🇳
In a spin-1 hadron, tensor-polarized parton distribution functions (PDFs) exist. The twist-2 function is $f_{1 LL}$ and a twist-3 one is $f_{L T}$ . Because an experiment is under preparation at the Thomas Jefferson National Accelerator Facility (JLab) to measure the cross section of electron-deuteron deep inelastic scattering with the tensor-polarized deuteron target, these PDFs need to be understood theoretically. Especially, measurements will be done in a relatively low- $Q^{2}$ region at JLab, so that twist-3 contributions could become sizable in the cross section. In a previous work, a twist-2 relation was derived for $f_{L T}$ in terms of $f_{1 LL}$ by using a nonlocal operator, and it corresponds to the Wandzura-Wilczek (WW) relation between $g_{1}$ and $g_{2}$ . In addition, another relation similar to the Burkhardt-Cottingham (BC) sum rule was obtained. It is known that a formal way to derive the WW relation and the BC sum rule is to use the operator product expansion (OPE) with local operators. In this work, the WW-like relation and the BC-like sum rule for $f_{L T}$ are derived by using the local OPE method as a reliable independent way to establish these relations.
Comments:
5 pages; v2, updated to match the published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2605.00430 [pdf]
PLB(2026)·1 citation
08
[Submitted on 1 May 2026] (cross-list from astro-ph.HE)
Maximal mass of neutron stars constrained by neutron star observations
Gábor Kasza🇭🇺 · György Wolf🇭🇺
We investigate constraints on the high-density equation of state (EOS) of neutron star matter by analyzing the probability distributions of the endpoints of mass-radius M(R) sequences within a Bayesian weighting framework. Starting from two representative hadronic baseline EOSs, SFHo and DD2, matched at higher densities to an extended linear sigma model description and constrained to approach perturbative QCD (pQCD) results, we construct families of causal hybrid EOSs spanning a broad range of stiffness at supranuclear densities. Observational constraints from the binary neutron-star merger GW170817, mass-radius measurements from the Neutron Star Interior Composition Explorer (NICER), and candidate low-mass and mass-gap compact objects are incorporated through Bayesian likelihood weighting. This approach allows us to determine probability distributions for the maximum neutron-star mass M $_{TOV}$ and the corresponding radius R $_{TOV}$ , i.e., the endpoints of the M(R) sequences. We find that the maximum-mass distributions are largely determined by observational constraints and show only weak sensitivity to the choice of baseline EOS, favoring values around 2.2-2.3 M $_{⊙}$ when the most robust constraints are applied. In contrast, the corresponding radius distributions exhibit a stronger dependence on the underlying hadronic EOS, with typical preferred values near $12 \pm 1$ km. Additional tidal-deformability constraints further restrict the allowed parameter space and disfavor very stiff EOS realizations when interpreted together with the possible mass-gap neutron-star candidate. Our results demonstrate that endpoint distributions of M(R) sequences provide a sensitive and complementary diagnostic for constraining the high-density behavior of the neutron-star EOS within a multimessenger Bayesian framework.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2605.00437 [pdf]
J.Subatomic Part.Cosmol.(2026)·1 citation
09
[Submitted on 1 May 2026] (cross-list from hep-ph)
Nuclear structure and saturation effects from diffractive vector meson production
Heikki Mäntysaari🇫🇮 · Hendrik Roch🇫🇮 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇨🇳
We study exclusive vector meson production in ultraperipheral collisions (UPCs) of a wide range of nuclei, and assess the potential of measurements to constrain the small- $x$ structure of oxygen and neon nuclei. We employ an impact-parameter-dependent color glass condensate framework incorporating JIMWLK evolution, with parameters constrained by a recent global Bayesian analysis of $γ + p$ and $γ + Pb$ data. We present predictions for coherent and incoherent $J / ψ$ production in $O + O$ and $Ne + Ne$ UPCs at LHC energies, and quantify theoretical uncertainties using posterior samples from the calibration. We employ several nuclear structure models and find that $t$ -differential observables are sensitive to the chosen model. We further study the mass-number dependence of saturation effects through nuclear suppression factors for coherent and incoherent vector meson production. Saturation-induced suppression increases systematically with both nuclear mass number and energy. Our results provide a unified framework for the systematic study of the onset of gluon saturation and nuclear structure at high energy, accessible in future UPC measurements at the LHC and at the Electron-Ion Collider.
Comments:
15 pages, 10 figures, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2605.00454 [pdf]
PRD(2026)·3 citations
10
[Submitted on 1 May 2026] (cross-list from physics.comp-ph)
MuDirac 1.3.0: A Sustainable Software Tool for Calculating Ground State Nuclear Properties Using Muonic X-Ray Measurements
Leandro Liborio · Milan Kumar · Subindev Devadasan · Philip Jones · Martin Plummer · Adrian Hillier · Albert Bartok
The nuclear charge radius is one of the most fundamental quantities of the atomic nucleus. It can be deduced from a combination of experimental measurements of muonicX-raytransitionenergieswithmodellingofthoseX-raytransitionenergies. In thisworkwepresentMuDirac (1.3.0), whichisanopen, publiclyavailable, sustainable and computationally efficient software tool that will be at put the disposal of the negative muon community. With MuDirac (1.3.0), the community will be able to accurately and efficiently estimate nuclear properties, such as the nuclear charge radius, by assuming a 2-parameter Fermi distribution of the nuclear charge.
Comments:
37 pages, 16 figures. Manuscript on use of negative muons for estimating nuclear properties
Subjects:
Computational Physics (physics.comp-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2605.00554 [pdf]
1 citation
11
[Submitted on 1 May 2026] (cross-list from hep-ph)
Stability of parton distributions at high $x$ : impact of nuclear and power corrections
C. Cocuzza🇺🇸 · W. Melnitchouk🇺🇸 · N. Sato🇺🇸 · A. W. Thomas🇦🇺
We present a comprehensive new global QCD analysis of unpolarized parton distribution functions (PDFs) based upon proton, deuteron and $A = 3$ data, including the latest inclusive deep-inelastic scattering (DIS) measurements from Jefferson Lab at high Bjorken- $x$ . Using the JAM Bayesian Monte Carlo framework, we systematically explore the stability of the PDFs with respect to variations in the cuts on the invariant mass $W$ of the DIS final state, the implementation of target mass and higher twist corrections, as well as on the nuclear wave functions for the $A = 2$ and 3 data. We find the $u$ and $d$ quark PDFs (and the $d / u$ ratio) are relatively stable up to $x \approx 0.8$ , and able to describe DIS data down to $W^{2} = 3.5$ GeV $^{2}$ and $Q^{2} = m_{c}^{2}$ . Within the collinear factorization framework, the fitted higher twist corrections to DIS are found to be positive, and largely isospin independent. The description of the nuclear data also requires nonzero isoscalar and isovector nucleon off-shell PDF contributions, which gives specific predictions for the ratio, $R_{D}$ , of deuteron to isoscalar nucleon structure functions.
Comments:
35 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2605.00666 [pdf]
5 citations

Affiliations

first authorsco-authorsvia INSPIRE