Nuclear Theory·nucl-th

Tuesday·August 25, 2026

22 papers—9 primary·13 cross-listed

10
[Submitted on 20 Aug 2026] (cross-list from hep-ph)
A Hydrogen-Like Model for Pion and Kaon Masses Based on Dirac Quark-Hamiltonians and Numerical Methods
Zhenhua Ning🇺🇸 · A. S. Davuluru🇺🇸 · H. Raposo🇺🇸 · Jong-Ping Hsu🇺🇸
We consider a relativistic hydrogen-like model for meson mass spectra. The model is based on a Lagrangian with a new general Yang-Mills symmetry. The strong interactions involve a fourth-order field equation that generates a linear confining potential. Notably, this model for meson masses requires quarks to carry only a single `confining charge' $f_{c}$ rather than three color charges. We classify meson mass spectra into sub-spectra defined by isospin, G-parity, total angular momentum and parity. By applying a numerical solver to the Dirac Hamiltonians--incorporating two short-range confining potentials, we obtain energy eigenvalues in natural units. The model has three coupling constants and one parameter. It provides a robust fit of 31 pions and kaons masses (from $\approx 140 M e V$ to $\approx 2, 300 M e V$ ) to within $\approx 18%$ of relative percentage error. The model suggests that the confining charge $f_{c}$ =0.045/MeV = 8.87 fm plays the role of the basic length in the quark interactions.
Comments:
11 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.21459 [pdf]
0 citations
11
[Submitted on 21 Aug 2026] (cross-list from hep-ph)
Photon production from gluon splitting and fusion induced by a magnetic field of arbitrary strength in relativistic heavy-ion collisions
Alejandro Ayala🇲🇽 · Santiago Bernal-Langarica🇲🇽 · José Jorge Medina-Serna🇲🇽 · Ana Julia Mizher🇧🇷
We compute the yield and elliptic flow coefficient for photons produced during the pre-equilibrium stage of semi-central relativistic heavy-ion collisions from the gluon fusion and splitting processes induced by the presence of a magnetic field. The calculation is performed for arbitrary values of the field strength. The pre-equilibrium gluon distribution is modeled with a glasma-inspired Bose-Einstein occupation factor, as well as with an anisotropic distribution that accounts for the rapid initial expansion along the beam axis. In both cases, we find a very good agreement between the calculation and the experimental data from PHENIX. Most notably, the shape and strength of the elliptic flow coefficient are described quite well, representing a step towards solving the outstanding photon puzzle.
Comments:
17 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2608.21600 [pdf]
0 citations
12
[Submitted on 22 Aug 2026] (cross-list from hep-ph)
Phase-constrained $Σ^{*}$ spectroscopy in the pure- $I = 1$ reactions $K_{L} p \to π^{+} Σ^{0}$ and $K_{L} p \to π^{+} Λ$
Dan Guo🇨🇳 · Marshall B. C. Scott🇺🇸 · Igor Strakovsky🇺🇸 · Fu-Rong Xu🇨🇳 · Bing-Song Zou🇨🇳
Low-energy $K ˉ N$ scattering provides direct access to strange-baryon spectroscopy, but conventional charged-kaon reactions mix the $I = 0$ and $I = 1$ amplitudes. Motivated by the isospin-selective nature of the $K_{L} p$ reactions, we present, to our knowledge, the first simultaneous analysis of the pure- $I = 1$ reactions $K_{L} p \to π^{+} Σ^{0}$ and $K_{L} p \to π^{+} Λ$ in which a common set of resonance parameters and a fixed relative-phase convention are imposed on both final states. Within an effective-Lagrangian model, a joint fit of available differential cross sections and recoil polarizations yields $χ^{2} / d.o.f. = 1.604$ . We find clear channel complementarity: the $t$ -channel $K^{*}$ exchange is more important in $K_{L} p \to π^{+} Λ$ , especially at forward angles, whereas $K_{L} p \to π^{+} Σ^{0}$ is more sensitive to the contribution of $Σ (1620) 1/ 2^{-}$ . At the same time, $Σ (1660) 1/ 2^{+}$ remains important through interference effects in both channels. These results demonstrate the importance of multichannel, phase-constrained analyses for establishing the $I = 1$ hyperon spectrum and provide timely phenomenological input for future high-precision measurements by the KLF program at JLab. Once the pure $I = 1$ amplitudes are reliably determined, they will also enable the separation of the $I = 0$ component in the much more abundant $K^{-} p \to π^{\pm} Σ^{\mp}$ data, opening a path toward a more quantitative study of the $Λ^{*}$ spectrum.
Comments:
6+8 pages, 3+4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.21824 [pdf]
0 citations
13
[Submitted on 23 Aug 2026] (cross-list from hep-ph)
Long-range scalar interactions in the effective field theory approach to $0 ν β β$
Fahim Ahmed🇺🇸
As a lepton-number-violating process whose observation would establish the Majorana nature of neutrinos, neutrinoless double-beta decay ( $0 ν β β$ ) is an important low-energy nuclear probe of beyond-the-Standard-Model physics. Effective field theory (EFT) provides a general, model-independent description, and interference among effective mechanisms is essential for disentangling their contributions to the total decay rate. We focus on scalar-type terms of the long-range Lagrangian in the EFT approach to $0 ν β β$ . We simultaneously retain the two scalar interactions involving a common $(S + P)$ leptonic current coupled either to an $(S - P)$ or an $(S + P)$ hadronic current. Their coherent contribution produces mutual interference between the two scalar mechanisms, controlled by the relative complex phase of their couplings, in addition to their separate interference with the standard mass mechanism. We give a compact half-life expression, the explicit scalar--scalar interference coefficient in terms of scalar nuclear-matrix-element ratios and integrated phase-space factors, and a positivity bound on that coefficient. The calculation uses the closure and single-nucleon impulse approximations, retains the dominant scalar recoil subset, and includes the $s_{1/2}$ and $p_{1/2}$ Coulomb waves of the outgoing electrons. The resulting dimensionally explicit formulation provides a basis for correlated analyses of the two scalar coefficients.
Comments:
29 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.22369 [pdf]
0 citations
14
[Submitted on 23 Aug 2026] (cross-list from hep-ph)
Eikonal Expansion for Classical Gluon Fields: from Weak to Strong
Shane Brown🇺🇸 · Alex DeBrizzi🇺🇸 · Alex Kovner🇺🇸
We develop a formal procedure of eikonal expansion for classical fields in gluodynamics. We show that in the weak field limit the expansion is straightforward and determines the eikonal components of vector potentials in terms of eikonal components of color currents via classical equations motion. We demonstrate that the recently proposed Born-Oppenheimer high energy evolution yields the ground state wave function interpretable in terms of the classical fields. The relevant classical field is indeed consistent with the eikonal expansion, and contains the leading eikonal and subeikonal components. For strong fields we find that the naive eikonal expansion is inconsistent, as nonlilearities in equations of motion lead to mixing of eikonal orders. Thus the effect of subeikonal components on the leading eikonal component is not suppressed by the eikonality parameter. We show that this problem can be rectified by classically "integrating out" high longitudional momentum components of gluon fields. This leads to a classical action for the low momentum components with small self interaction, but strongly renorlamized currents, which contain contribution due to high momentum modes.
Comments:
41 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.22536 [pdf]
0 citations
15
[Submitted on 23 Aug 2026] (cross-list from hep-ph)
Charmonia at Finite Momentum and Spatial Correlators in Quark-Gluon Plasma
Thomas Hardin🇺🇸 · Ralf Rapp🇺🇸
Spatial correlation functions of quarkonia in the quark-gluon plasma are available from finite- temperature lattice-QCD with good precision. However, their interpretation in terms of microscopic spectral functions has been challenging due to a highly oscillating momentum integral in their Fourier transform and the need for a reliable evaluation of their 3-momentum dependence. Utilizing the thermodynamic T-matrix approach we first obtain a Lorentz-covariant scattering equation by taking advantage of a separable-potential approximation. Medium effects are included through state-of-the- art heavy-quark selfenergies and a potential screening which we constrain by euclidean correlators from lattice QCD. In addition to the usual two-particle cut in the scattering equation we also include particle-hole excitations, also referred to as zero mode. We find that both the increase of euclidean correlators with 3-momentum and the suppression of the spatial correlators found in lattice-QCD can be qualitatively reproduced, with the zero mode playing an essential role for the former but not for the latter.
Comments:
8 pages and 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.22596 [pdf]
0 citations
16
[Submitted on 24 Aug 2026] (cross-list from hep-ph)
Revisiting the $Λ (1405)$ pole structure with convolutional neural networks
Julius B. Pagayon · Vince Angelo A. Chavez · Denny Lane B. Sombillo
We revisit the long-standing ambiguity surrounding the complex pole structure of the $Λ (1405)$ resonance by reframing it as a classification problem for convolutional neural networks (CNNs). By training our models to recognize subtle geometric variations on nearly degenerate lineshapes using targeted differential feature on empirical CLAS data, we establish a data-driven consensus on large inference samples. Our results show that the analytic structure characterized by two poles on the $[b t]$ sheet and additional pole on the $[bb]$ sheet globally dominates. The inference-guided pole parameter extraction reveals that the $Λ (1405)$ is a two-state system, characterized by a molecular state sitting below the $K ˉ N$ threshold and a non-molecular state lying above the $Σ π$ threshold.
Comments:
14 pages, 5 figures, comments are welcome
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2608.22747 [pdf]
0 citations
17
[Submitted on 24 Aug 2026] (cross-list from hep-ph)
$Δ$ resonance contributions to QED radiative corrections in neutron and inverse beta decay
Oleksandr Tomalak🇨🇳 · Yi-Bo Yang🇨🇳
We incorporate the $Δ (1232)$ resonance into pion-induced QED radiative corrections to neutron decay and inverse beta decay (IBD). Within the framework of heavy-baryon chiral perturbation theory with explicit $Δ$ degrees of freedom, we compute additional contributions and study their impact on IBD cross sections and on the renormalization of the nucleon isovector vector and axial-vector charges. $Δ$ resonance does not renormalize the vector charge. For the axial-vector charge, including the $Δ$ resonance restores power counting and significantly reduces the QED radiative correction to the experiment-over-lattice-QCD ratio $g_{A} / (g_{A}^{QCD} g_{V})$ , bringing it to zero within radiative-correction uncertainties. $Δ$ resonance increases the pion-induced QED radiative corrections to IBD by a factor $1.2$ - $1.3$ .
Comments:
19 pages, 1 figure
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:
2608.22845 [pdf]
0 citations
18
[Submitted on 24 Aug 2026] (cross-list from astro-ph.HE)
Neutron star masses from electron-capture supernovae under equation-of-state uncertainties
Vishal Parmar · Domenico Scordino · Ignazio Bombaci
Electron-capture supernovae (ECSNe) are a promising formation channel for low-mass neutron stars, but the minimum gravitational mass of the neutron stars they produce depends on both the progenitor core structure and the neutron-star matter equation of state (EOS). We compute the electron-capture (EC) threshold gravitational mass ( $M_{W D}^{⋆}$ ) of cold white-dwarf-like O--Ne--Mg cores with representative compositions and map the baryon number onto cold neutron-star configurations constructed from a Bayesian ensemble of unified crust--core EOSs. Although the EC threshold density is sensitive to the concentrations of the O--Ne--Mg mixture, the threshold baryon number of the O--Ne--Mg core varies only weakly, producing a narrow remnant-mass window. In the baseline case with no baryonic mass loss during the transition from the EC threshold mass O--Ne--Mg core to the remnant neutron star, standard ECSNe yield remnant neutron stars with gravitational masses of $1.24$ -- $1.265 M_{⊙}$ , with only a small EOS-induced spread. Small baryonic mass losses of $0.01$ -- $0.02 M_{⊙}$ shift this range modestly downward, but the $1.174 M_{⊙}$ companion of PSR J0453+1559 would require an extreme mass loss close to $0.10 M_{⊙}$ , which is not favored by current ECSN simulations. We find that the residual EOS dependence of the remnant mass is controlled mainly by the pressure around nuclear saturation density, while the corresponding tidal deformability remains sensitive to the remnant radius and compactness. Thus, low-mass double neutron star systems can in principle connect ECSN-like formation channels with gravitational-wave constraints on the EOS. Our results show that ECSNe naturally form low-mass neutron stars, but within a restricted mass range; the lightest observed neutron stars likely require low-mass iron-core collapse, ultra-stripped supernovae, or other nonstandard channels.
Comments:
12 pages, 6 figures. To appear in A&A
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2608.23122 [pdf]
0 citations
19
[Submitted on 24 Aug 2026] (cross-list from hep-ph)
Radiative decays of the isoscalar $S$ -wave $D D ˉ$ molecule
Yuan-Jun Gao🇨🇳 · Gang Li🇨🇳 · Shi-Dong Liu🇨🇳 · Pan-Pan Shi🇪🇸
In the hadronic molecular picture, an isoscalar $S$ -wave $D D ˉ$ molecule is naturally expected as the spin-0 partner of $X (3872)$ . Assuming this state, denoted by $X_{0}$ , to be a pure $D D ˉ$ molecule with quantum numbers $J^{P C} = 0^{++}$ , we investigate its radiative decays $X_{0} \to γ V (V = ρ^{0}, ω)$ within an effective Lagrangian framework. The decay amplitudes are generated by intermediate charmed-meson loops, with electromagnetic gauge invariance consistently maintained throughout the calculation. We evaluate the partial decay widths and examine their dependence on the $X_{0}$ mass and the cutoff. Although the individual decay widths exhibit a sizable dependence on the cutoff, their ratio is remarkably stable. In particular, we obtain that the ratio for the decays $X_{0} \to γ ρ^{0}$ and $X_{0} \to γ ω$ is approximately 2.26, which is insensitive to the variation of the cutoff. This robust ratio provides a useful model-insensitive signature of the molecular structure of $X_{0}$ .
Comments:
9 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2608.23332 [pdf]
0 citations
20
[Submitted on 24 Aug 2026] (cross-list from hep-th)
Landau theory, effective temperature, and tricritical phenomena in a holographic nonequilibrium steady state
Motohiro Kanazawa🇯🇵 · Masataka Matsumoto🇯🇵 · Shin Nakamura🇯🇵
We investigate the critical exponents $(γ, ν)$ at the current-driven tricritical point (TCP) associated with chiral symmetry breaking in a nonequilibrium steady state described by the D3/D7 model. In the symmetry-broken phase, we find that, unlike in the conventional Landau theory, both $γ$ and $ν$ can take values different from those predicted by the Landau theory and depend on the path along which the TCP is approached in the phase diagram. However, when the TCP is approached with the ratio of the effective temperature to the heat bath temperature, $T_{*} / T$ , held fixed, the critical exponents agree with those of the Landau theory. These results suggest that the critical phenomena at the current-driven TCP may be described by the Landau theory along the $T_{*} / T$ -fixed line, whereas a nontrivial extension of the Landau theory is required for a more general description of the critical phenomena along arbitrary paths.
Comments:
20 pages, 9 figures
Subjects:
High Energy Physics — Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2608.23378 [pdf]
0 citations
21
[Submitted on 24 Aug 2026] (cross-list from hep-ph)
Imprints of nuclear shell structure in exclusive vector meson production
Arpita Mondal🇮🇳 · Arjun Kumar🇺🇸 · Debojit Sarkar🇮🇳
We report for the first time that, within the saturation framework, exclusive vector meson production at small $x$ is sensitive to the shell structure of the target nucleus. Self-consistent nuclear densities from occupied single-particle orbitals in the quark-meson coupling (QMC) model modify the coherent $∣ t ∣$ -differential cross section, enhancing the secondary diffractive lobes for light nuclei and displacing the higher-order minima in $∣ t ∣$ for intermediate-mass nuclei, whereas for heavy targets the shifts are weaker and appear at larger $∣ t ∣$ . Because the small $J / ψ$ dipole is insensitive to saturation, these features make coherent $J / ψ$ production a clean probe of nuclear shell structure, most favorably for intermediate-mass nuclei such as the calcium isotopes. For the larger $ϕ$ dipole, shell structure must be included in the nuclear initial state before saturation effects can be isolated in differential observables at the EIC. Our results establish exclusive vector meson production as a probe of the mean-field, single-particle structure of nuclei at small $x$ , and provide a baseline for isolating residual many-body correlations.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2608.23445 [pdf]
0 citations
22
[Submitted on 24 Aug 2026] (cross-list from nucl-ex)
Core Breaking at Low Spin in $^{68}$ Zn from Nuclear Resonance Fluorescence
S. R. Johnson · R. V. F. Janssens · B. A. Brown · A. D. Ayangeakaa · S. S. Bhattacharjee · E. Churchman · S. W. Finch · U. Friman-Gayer · S. Frye · M. Fulghieri · D. Gribble · X. H. -K. James · R. Longland · C. Wegner
Low-spin excited states in $^{68}$ Zn have been studied at the High Intensity Gamma-Ray Source (HI $γ$ S) from the ground state up to the particle emission threshold using the nuclear resonance fluorescence technique (NRF) and the newly developed Clover Array. Low-spin levels were excited by linearly-polarized, $2.90 - 9.79$ MeV photon beams. Spin-parity quantum numbers as well as associated $M 1$ and $E 1$ decay strengths were determined for a large fraction of the 158 states observed. In addition, long-duration coincidence measurements at 9.46 and 9.79 MeV enabled the investigation of the level scheme near the ground state. The results have been interpreted with shell-model calculations using two different model spaces and several effective interactions often used to describe nuclei in this mass region. While the structure near the ground state can be understood in terms of excitations involving solely valence nucleons, core breaking is required to account for the evolution of the total $M 1$ strength at excitation energies above $\sim 5$ MeV.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2608.23514 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE