Nuclear Theory·nucl-th

Tuesday·April 28, 2026

14 papers—5 primary·9 cross-listed

06
[Submitted on 24 Apr 2026] (cross-list from hep-ph)
Compositeness of near-threshold states in charged hadronic systems
Tomon Kinugawa🇯🇵 · Tetsuo Hyodo🇯🇵
We quantify the internal structure of near-threshold bound, virtual, and resonance states in systems where Coulomb and short-range interactions coexist by evaluating the compositeness. Using the Coulomb-modified effective range expansion, we derive an expression for the compositeness in terms of the eigenenergy and Coulomb effective range in the weak-binding limit. We then apply the formulation to several near-threshold states in hadronic and nuclear systems, including $pp$ , $α α$ , $Ω^{-} Ω^{-}$ , $Ω_{ccc}^{++} Ω_{ccc}^{++}$ , $Ξ^{-} α$ , and $Ω^{-} p$ .
Comments:
4 pages, Proceedings of the 2025 International Conference on the Structure of Baryons (Baryons 2025), November 10th - 14th, 2025
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.22250 [pdf]
J.Subatomic Part.Cosmol.(2026)·0 citations
07
[Submitted on 24 Apr 2026] (cross-list from hep-ph)
Amplitude-Based Analysis of QED Radiative Corrections to Electroproduction of $η$ -Mesons on Protons
Isabella Illari🇺🇸 · Andrei Afanasev🇺🇸 · William J. Briscoe🇺🇸 · Victor L. Kashevarov🇮🇹 · Axel Schmidt🇺🇸 · Igor I. Strakovsky🇺🇸
A formalism for radiative correction calculations in exclusive $η$ electroproduction on the proton is presented, extending the treatment developed for the pion channel. The EXCLURAD code is used in the radiative correction procedure with EtaMAID-2023 multipole amplitudes. The cross-section correction factor $δ$ varies by up to $\sim 30%$ across the resonance region $W = 1.49$ - $2.0$ GeV at $E_{beam} = 6.535$ GeV, with a local maximum near $W ≃ 1.66$ GeV driven by the $S_{11} (1535)$ and $S_{11} (1650)$ resonances. The beam-spin asymmetry is suppressed by 15-25% at the same kinematics. Numerical results covering $Q^{2} = 0.3$ - $4.0$ GeV $^{2}$ and the full angular range are provided for kinematics relevant to CLAS12 experiments at Jefferson Lab.
Comments:
30 pages, 28 figures; includes supplemental material; to be submitted to Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2604.22943 [pdf]
0 citations
08
[Submitted on 25 Apr 2026] (cross-list from hep-ph)
Possible Evidence for Neutral Color-Singlet $q q ˉ$ Quark Matter from High-Energy Pb-Emulsion Collisions
Cheuk-Yin Wong🇺🇸
The invariant mass spectrum of $e^{+} e^{-}$ pairs produced in high-energy Pb-emulsion collisions at 160 A GeV at CERN SPS exhibits a highly complex structure of a broad enhancement at 11 $\pm$ 1 MeV with a full width of about 10 MeV, and additional many narrow resonances within the experimental bin width of 2 MeV, including a prominent narrow resonance at 19 $\pm$ 1 MeV that provides an independent support for the hypothetical X17 particle. We show that the highly complex spectrum may be coherently described as the signatures for the neutral color-singlet $q q ˉ$ quark matter in both its deconfined phase as well as its confined phase. That is, the broad enhancement at 11 $\pm$ 1 MeV may arise from thermal annihilation of QED(U(1))-deconfined quarks and antiquarks into $e^{+} e^{-}$ pairs at the phase transition temperature $T_{c}$ (QED), which can be theoretically estimated to be 4.75 $\pm$ 1.04 MeV from the transitional equilibrium condition. The observed narrow resonances at 3 $\pm$ 1 and 7 $\pm$ 1 MeV may correspond to the QED(U(1))-deconfined $u u ˉ$ and $d d ˉ$ Coulomb bound states near their quark rest masses, respectively, whereas the observed narrow resonance at 19 $\pm$ 1 MeV may correspond to the QED(U(1))-confined isoscalar QED meson. The approximate agreement between the theoretical and the experimental spectrum suggests tentatively that both QED(U(1))-confined and QED(U(1))-deconfined neutral color-singlet $q q ˉ$ quark matter may have been produced in these high-energy Pb-emulsion collision, pending confirmation of the Pb-emulsion collision data. We propose future experiments to confirm or refute these findings.
Comments:
30 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2604.23473 [pdf]
0 citations
09
[Submitted on 26 Apr 2026] (cross-list from hep-ph)
Three regimes/phases of QCD at high T, their symmetries and N_c scaling
L. Ya. Glozman
We review recent developments on the QCD phase diagram at small chemical potentials and increasing temperature. There are three regimes/phases in QCD which differ by symmetries, degrees of freedom and N_c scaling: the hadron gas below the chiral restoration temperature T_ch, the stringy fluid between T_ch and the deconfinement temperature T_d and the quark-gluon plasma above T_d.
Comments:
5 double-column pages. Invited talk at (i) Exploring QCD matters at high temperatures and densities, BNL, February 2-4, 2026; (ii) 16th Workshop on critical point and onset of deconfinement, CERN, April 13-17, 2026; (iii) Buenas ideas on QCD phase diagram, Yukawa Institute, Kyoto, May 26-29, 2026
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2604.23689 [pdf]
0 citations
10
[Submitted on 26 Apr 2026] (cross-list from hep-th)
Weyl anomaly induced transport in hydrodynamics
Shi-Zheng Yang🇨🇳 · Jian-Hua Gao🇨🇳 · Zuo-Tang Liang🇨🇳 · Georgy Yu. Prokhorov🇷🇺 · Shi Pu🇨🇳 · Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺
We show that the Weyl (trace) anomaly gives rise to a new non-dissipative vector current in accelerated relativistic fluids. The anomaly uniquely fixes the second-order transport coefficient governing the coupling between the electromagnetic field and the fluid acceleration. We derive this result by extending hydrodynamic anomaly matching to include the trace anomaly, and independently reproduce it in boundary quantum field theory by treating the Rindler horizon of an accelerated observer as an effective boundary. From the boundary perspective, the electric- and magnetic-field sectors correspond to screening and vacuum magnetization effects near the boundary. In the local rest frame, the electric-field contribution induces an additional charge density, while the magnetic-field contribution generates a transverse current with a Nernst-like, more generally thermomagnetic Hall-like, tensor structure. Our results reveal a new class of anomaly-induced transport governed by the trace anomaly.
Comments:
6 pages, 2 figures
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.23849 [pdf]
1 citation
11
[Submitted on 27 Apr 2026] (cross-list from nucl-ex)
Hard Probes in Ultraperipheral Collisions at LHCb
Krista Smith (on behalf of the LHCb Collaboration)🇰🇷
Measurements of quarkonia production in peripheral and ultraperipheral heavy-ion collisions are sensitive to photon-photon and photon-nucleus interactions, the partonic structure of nuclei, and the mechanisms of vector-meson production. In this contribution, quarkonium measurements with the highest precision currently accessible will be compared with the latest theoretical models. Additionally, new studies of $ρ (770)$ and $ϕ (1020)$ vector meson production at forward rapidity will be presented and contrasted with other experimental results. Future UPC measurements with the upgraded LHCb detector in Run 3 will also be discussed.
Comments:
Contribution to: Quark Matter 2025
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2604.23955 [pdf]
EPJ Web Conf.(2026)·0 citations
12
[Submitted on 27 Apr 2026] (cross-list from hep-ph)
Selected Topics in Quark-Hadron Physics: From Scalar Nonets to Topological Glueballs
Chihiro Sasaki🇵🇱
This contribution reviews recent progress in the low-lying scalar mesons and glueballs. We propose a new classification for the scalar nonet that includes $f_{0} (980)$ and $a_{0} (980)$ as the lowest states, while we identify $f_{0} (1500)$ as a primary glueball candidate. We demonstrate that the production yields of these states in heavy-ion collisions are mutually consistent across statistical, coalescence, and S-matrix frameworks. To investigate their internal structure, we move beyond standard phenomenology by describing glueballs as topological solitons. This approach yields an energy spectrum in excellent agreement with lattice QCD and experimental data, while interpreting $f_{0} (2470)$ as a tightly bound glueballonium to explain its anomalously long lifetime. This non-perturbative framework provides a predictive basis for the future experimental verification of exotic scalar states.
Comments:
10 pages, 4 figures, prepared for the proceedings of the 66th Cracow School of Theoretical Physics "Physics of Strong Interactions under Extreme Conditions"
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.24177 [pdf]
Acta Phys.Polon.B(2026)·0 citations
13
[Submitted on 27 Apr 2026] (cross-list from hep-ph)
Non-perturbative heavy quark diffusion coefficients in arbitrarily magnetized quark-gluon plasma
Debarshi Dey🇨🇳 · Aritra Bandyopadhyay🇵🇱 · Yifeng Sun🇨🇳 · Santosh K. Das🇮🇳
Heavy quark (HQ) momentum ( $κ$ ) and spatial diffusion ( $D_{s}$ ) coefficients are computed in a non-perturbative thermal QCD medium in the presence of a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated via the in-medium HQ potential, obtained from the resummed gluon propagator. We find that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction defining the axis of anisotropy. This anisotropy originates from restrictions on longitudinal momentum diffusion in the gluon spectral function, and naturally leads to two spatial diffusion coefficients ( $D_{s}^{L}$ , $D_{s}^{T}$ ). Non-perturbative effects are found to be dominant at low temperatures. These results provide a more consistent input for Langevin based calculations of the heavy quark directed flow at RHIC and LHC energies.
Comments:
7 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.24535 [pdf]
PLB(2026)·0 citations
14
[Submitted on 27 Apr 2026] (cross-list from hep-ph)
On the Two $R$ -Factors in the Small- $x$ Shockwave Formalism
Yuri V. Kovchegov🇺🇸 · M. Gabriel Santiago🇺🇸 · Huachen Sun🇺🇸
There are two $R$ -factors frequently used in the phenomenology of exclusive processes at small values of the Bjorken $x$ variable. One $R$ -factor takes into account the effects of non-zero longitudinal momentum transfer, which is assumed to be zero in the dipole scattering amplitude. Another $R$ -factor accounts for the real part of the elastic scattering amplitude which is often neglected, with the standard dipole scattering amplitude giving only the imaginary part of the elastic amplitude. In this work we present two new theoretical developments aimed at eliminating the need for the two $R$ -factors. We argue that the $R$ -factors can be replaced by (i) modifying the argument of the dipole scattering amplitude and by (ii) augmenting the initial conditions for its non-linear small- $x$ evolution. Specifically, we show that to account for the effects of non-zero skewness $ξ$ , one has to replace the rapidity argument $Y = ln (1/ x)$ of the eikonal dipole amplitude $N$ and the odderon dipole amplitude $O$ by $Y = ln min {1/∣ x ∣, 1/∣ ξ ∣}$ . The prescription applies to the elastic scattering cross sections, as well as for calculations of the Generalized Parton Distributions and Generalized Transverse Momentum Dependent parton distributions at small $x$ and at small but non-zero skewness $ξ$ . We also show that the real part of the scattering amplitude, proportional to Im~ $N$ , which is intimately connected to the signature factor of the amplitude, can be accounted for by a more careful evaluation of the initial condition for the evolution and by writing the non-linear evolution equation in an integral form. One can similarly construct Im~ $O$ for the odd-signature odderon amplitude. We hope that future implementation of our prescriptions presented here will eliminate the need for both phenomenological $R$ -factors.
Comments:
35 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.24629 [pdf]
4 citations

Affiliations

first authorsco-authorsvia INSPIRE