Nuclear Theory·nucl-th

Monday·April 20, 2026

12 papers—4 primary·8 cross-listed

01
[Submitted on 17 Apr 2026]
Novel microscopic approaches for Spin-Isospin excitations and Beta-decay
Hiroyuki Sagawa
We explore unsolved nuclear structure problems related with the spin and isospin degree of freedom by using microscopic models which accommodate realistic isoscalar and isovector pairing interactions, and also tensor correlations. For the attempt of universal theoretical framework for both nuclear and astrophysical phenomena, we adopt a self-consistent Hartree-Fock (HF)+random phase approximation (RPA) models, and a state-of-the-art beyond mean field model, Subtracted Second RPA (SSRPA), including the couplings to two-particle two-hole states. The quenching problems of magnetic dipole and Gamow-Teller transitions are discussed in terms of the coupling to 2p-2h configurations and also the tensor correlations. The $β$ decay life time of semi-magic and magic nuclei are discussed in RPA and SSRPA models.
Comments:
9pages,5figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.15817 [pdf]
EPJ Web Conf.(2026)·0 citations
02
[Submitted on 17 Apr 2026]
Charge radii of Sn isotopes in the relativistic mean field approximation
S. Marcos · N. Sandulescu · R. Niembro
The kink observed in the nuclear charge radius of Sn isotopes around neutron number $N = 82$ is investigated within the relativistic mean-field (RMF) framework using the NL3 $^{*}$ parameter set. It is shown that the small components of the Dirac spinors for the neutron single-particle states near the Fermi level play a crucial role in forming the kink through their contribution to the proton central potential. In particular, the significant differences between the radial parts of the small components of spin-orbit partner states make neutrons with $j = l - 1/2$ more efficient in increasing the nuclear charge radius than those with $j = l + 1/2$ . However, the effect induced by the small components alone does not fully account for the magnitude of the kink observed in Sn isotopes.
Comments:
to be published in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.15904 [pdf]
PRC(2026)·0 citations
03
[Submitted on 17 Apr 2026]
Charged-current quasielastic-like neutrino scattering from $^{12}$ C in the coherent density fluctuation model with two-nucleon emission
M. V. Ivanov🇧🇬 · A. N. Antonov🇧🇬
The quasielastic cross-sections of charged-current neutrino and antineutrino scattering on $^{12}$ C are calculated using the coherent density fluctuation model with a relativistic effective mass $m_{N}^{*} = 0.8 m_{N}$ (CDFM $_{M^{*}}$ ). The model explicitly considers the modification of the relativistic effective mass of the nucleon within the relativistic mean field (RMF) model of nuclear matter. In addition, our calculations include neutrino-induced two-particle emission processes, which are evaluated within the RMF model of nuclear matter. Utilizing the CDFM $_{M^{*}}$ , we provide predictions for the neutrino and antineutrino cross sections of $^{12}$ C, which have been observed in accelerator experiments, such as MiniBooNE, T2K, and MINERvA. Also, we analyze the axial form factor value for the excitation of the $Δ$ at zero momentum transfer (commonly denoted as $C_{5}^{A} (0)$ ) which is important for the treatment of the $Δ$ current in the meson-exchange currents (MEC) calculation. In addition, the quasielastic results obtained within CDFM $_{M^{*}}$ model are thoroughly evaluated for different regions of the momentum transfer.
Comments:
14 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.15989 [pdf]
PRC(2026)·0 citations
04
[Submitted on 17 Apr 2026]
Sensitivity of the $^{3, 4}$ He( $K^{-}$ , $π^{0}$ ) production ratio to the $Λ$ binding energy of $_{Λ}^{3}$ H
Toru Harada🇯🇵 · Yoshiharu Hirabayashi🇯🇵
We study the production of $_{Λ}^{3}$ H and $_{Λ}^{4}$ H in the $^{3, 4}$ He( $K^{-}$ , $π^{0}$ ) reactions at $p_{K^{-}} = 1.0$ ~GeV/ $c$ within the distorted-wave impulse approximation, using the optimal Fermi-averaged $K^{-} p \to π^{0} Λ$ amplitude. Because the $_{Λ}^{3}$ H ground state is extremely weakly bound, the $d$ -- $Λ$ wave function becomes spatially extended. We calculate the integrated cross sections $σ_{lab}$ and their ratio $R_{34} = σ_{lab} (_{Λ}^{3} H) / σ_{lab} (_{Λ}^{4} H)$ for forward angles $θ_{lab} = 0^{\circ}$ -- $2 0^{\circ}$ . The production strength of $_{Λ}^{3}$ H and the ratio $R_{34}$ are strongly sensitive to the $Λ$ binding energy $B_{Λ}$ , which is constrained to be approximately 0.05--0.15~MeV by comparison with experimental data from the J-PARC E73 experiment. This indicates that the $^{3}$ He( $K^{-}$ , $π^{0}$ ) reaction provides a sensitive probe of the weak binding of $_{Λ}^{3}$ H.
Comments:
3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2604.16181 [pdf]
0 citations
05
[Submitted on 16 Apr 2026] (cross-list from hep-th)
Systematic Analytic Regularization in $φ^{4}$ and Yukawa Theories
Jarryd Bath🇿🇦 · W. A. Horowitz🇺🇸
We introduce a novel regularization scheme: Systematic Analytic Regularization (SAR). SAR regularizes a theory at the level of the action by analytically continuing the power of the kinetic operator, ensuring that the theory is formally finite before any terms in the Dyson series are evaluated. We demonstrate that SAR fully and self-consistently regularizes $φ^{4}$ and Yukawa theories at NLO.
Comments:
16 pages
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.15429 [pdf]
0 citations
06
[Submitted on 17 Apr 2026] (cross-list from nucl-ex)
sPHENIX measurement of Open-Charm Baryon-to-Meson Ratios in $p$ + $p$ collisions at RHIC
Xudong Yu (on behalf of the sPHENIX Collaboration)🇨🇳
sPHENIX is a state-of-the-art experiment at the Relativistic Heavy Ion Collider (RHIC), dedicated to the study of heavy-flavor and jet physics. Its precision tracking system, combined with streaming readout, enables heavy-flavor measurements with high-statistics and essentially unbiased data samples. During the 2024 run, sPHENIX was fully commissioned and recorded a sample of 100 billion unbiased $p$ + $p$ collisions, together with a minimum-bias Au+Au dataset. The 2025 run further expanded the sPHENIX dataset with high-statistics $p$ + $p$ , O+O and Au+Au collisions. This extensive $p$ + $p$ sample opens the door to heavy-flavor measurements with orders of magnitude more statistics than previously available at RHIC. Notably, there has been no prior measurement of the $Λ_{c}^{+} / D^{0}$ baseline in $p$ + $p$ collisions at RHIC energies. The large sPHENIX dataset now enables the first exploration of key open questions, such as the hadronization mechanism of baryons and the strange-to-light flavor meson ratio.
Comments:
5 pages, 3 figures, proceedings for Baryons 2025 conference
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2604.15667 [pdf]
J.Subatomic Part.Cosmol.(2026)·0 citations
07
[Submitted on 17 Apr 2026] (cross-list from hep-ph)
Theoretical modeling of charged current $ν_{μ} (ν ˉ_{μ}) -^{40} A r$ DIS at DUNE energies
F. Zaidi🇮🇳 · S. Akther🇮🇳 · M. Sajjad Athar🇮🇳 · S.K. Singh🇮🇳
The charged current $ν_{μ} (ν ˉ_{μ})$ -induced deep inelastic scattering (DIS) from an $^{40} Ar$ target is studied using a microscopic framework that incorporates nuclear medium effects due to Fermi motion, binding energy, nucleon correlations, mesonic ( $π$ and $ρ$ ) contributions, and nuclear shadowing and antishadowing across the relevant Bjorken- $x$ region. The nuclear structure functions $F_{i A} (x, Q^{2})$ $(i = 1 - 3)$ are evaluated using a relativistic nucleon spectral function ( $S_{h}$ ) within the local density approximation employing the free nucleon structure functions, $F_{i N} (x, Q^{2})$ $(i = 1 - 3)$ . These $F_{i N} (x, Q^{2})$ $(i = 1 - 3)$ are calculated using parton distribution functions (PDFs) from MMHT 2014 parameterization, including higher-order perturbative QCD corrections up to next-to-next-to-leading order (NNLO), along with nonperturbative target mass corrections (TMC). The resulting nuclear structure functions $F_{i A} (x, Q^{2})$ $(i = 1 - 3)$ are subsequently used to compute the differential DIS cross sections for $^{40} A r$ nucleus. Numerical results are presented for $ν_{μ} (ν ˉ_{μ})$ beam energies $E = 4$ GeV and $E = 6$ GeV for the differential scattering cross sections $\frac{d ^{2} σ}{d x d y}$ and $\frac{d σ}{d x}$ , relevant to ongoing and upcoming liquid-argon neutrino experiments such as DUNE and the Fermilab Short-Baseline Neutrino program.
Comments:
17 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2604.15724 [pdf]
PRD(2026)·0 citations
08
[Submitted on 17 Apr 2026] (cross-list from hep-ph)
P-wave $c c ˉ$ meson contributions in exotic hadrons
Kotaro Miyake🇯🇵 · Yasuhiro Yamaguchi🇯🇵
The nature of the $X (3872)$ and other exotic hadrons has been a subject of extensive investigation. While various theoretical models have been proposed, experimental evidence suggests that the $X (3872)$ may be a mixture state of a hadronic molecule and a $c c ˉ$ core. In this work, we perform a systematic study of hidden-charm tetraquark candidates $X (3860)$ , $X (3872)$ , and $Z (3930)$ using a coupled-channel model that incorporates both $c c ˉ$ states and $D^{(*)} D ˉ^{(*)}$ hadronic molecular components. The model parameters are fixed to reproduce the masses of the $X (3872)$ and $Z (3930)$ , and the resulting framework is used to predict the mass and structure of the $0^{++}$ state associated with the $X (3860)$ . Our results support the mixture interpretation of these exotic hadrons, exhibiting strong attractions from the transition potential between $c c ˉ$ and $D^{(*)} D ˉ^{(*)}$ components. The molecular component dominates in the $X (3872)$ , while the $c c ˉ$ component plays a more prominent role in the $X (3860)$ and $Z (3930)$ .
Comments:
4 pages, Proceedings of the 2025 International Conference on the Structure of Baryons (Baryons 2025), 10-14 Nov. 2025
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.15778 [pdf]
J.Subatomic Part.Cosmol.(2026)·1 citation
09
[Submitted on 17 Apr 2026] (cross-list from hep-ph)
Delineating neutral and charged mesons in magnetic fields
Toru Kojo🇯🇵 · Sakura Itatani🇯🇵
We investigate the properties of neutral and charged mesons in magnetic fields, from weak-field to strong-field regimes. To develop analytic insights, we employ a non-relativistic quark model with a confining potential of the harmonic oscillator type. Short-range correlations, such as Coulomb and color-magnetic interactions, are treated as perturbations. In particular, we focus on the magnetic field dependence of the relative and the center-of-mass motions. The qualitative trends differ significantly between neutral and charged mesons: for neutral mesons, the transverse momenta are conserved and continuous, while charged mesons exhibit quantized transverse dynamics. The Zeeman effects, arising from intrinsic spins and orbital angular momenta, are carefully examined. In particular, for charged mesons with spins $s \geq 1$ , we discuss how the zero-point energy in the internal quark motion cancels the Zeeman energy from the orbital angular momentum, ensuring the energetic stability of mesons with high spins. The effectively reduced dimensionality of these mesons in the strong-field limit is also discussed.
Comments:
17 pages, 8 figures; v2 typo corrected, published in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2604.15897 [pdf]
PRD(2026)·2 citations
10
[Submitted on 17 Apr 2026] (cross-list from hep-th)
Exact expectation values in a boost-invariant fluid of Dirac fermions with finite spin density
Andrea Palermo🇫🇷 · Daniele Roselli🇮🇹
We study a boost-invariant, out-of-equilibrium fluid of non-interacting Dirac fermions with a finite canonical spin potential. After solving the Dirac equation in Milne coordinates, we exactly diagonalize the non-equilibrium density operator and compute the partition function and expectation values of relevant observables, including spin polarization, energy density, longitudinal and transverse pressures, spin density, and \emph{spin torque}, i.e. the source of spin non-conservation. We find an analytic expression for the partition function at finite spin potential, and show numerically that thermodynamic relations connecting it to thermodynamic functions hold in the system under consideration. We show that, in a boost-invariant system, both shear-induced polarization and the spin Hall effect are absent, and that a non-vanishing polarization can only arise from a finite spin potential in a free theory. We obtain an analytic expression for the spin polarization as a function of the spin potential in some particular cases, and otherwise compute numerically its exact expectation value at finite spin potential. Our results are discussed in the context of relativistic spin hydrodynamics and quark--gluon plasma phenomenology.
Comments:
Main text: 36 pages and 2 figures. Appendices: 15 pages
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2604.15926 [pdf]
JHEP(2026)·1 citation
11
[Submitted on 17 Apr 2026] (cross-list from hep-th)
Testing Scalar Field Self-Dualities in d=2 using a Variational Method
Paul Romatschke🇦🇹 · Ulrike Romatschke🇦🇹
Recently, self-dualities based on saddle-point expansions have been proposed as a means to obtain qualitative non-perturbative information in scalar field theories. In this work, we test this proposition quantitatively by studying the phase transition for critical scalar $ϕ^{4}$ field theory in 1+1 dimensions using a variational method. We find that saddle-point methods obtain quantitative agreement for the free energy, but differ on the order of 25 percent for the peak location of the correlation length.
Comments:
17 pages, 3 figures
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2604.15988 [pdf]
PRD(2026)·0 citations
12
[Submitted on 17 Apr 2026] (cross-list from nucl-ex)
Isospin-symmetry violation -- kaons and beyond (ISO-BREAK 25: summary and outlook)
Marek Gazdzicki (1)🇵🇱 · Francesco Giacosa (1)🇵🇱 · Katarzyna Grebieszkow (2)🇵🇱 · David Blaschke (3)🇵🇱 · Marcus Bleicher (4)🇩🇪 · Bastian Brandt (5)🇩🇪 · Wojciech Brylinski · Tobiasz Czopowicz (6)🇵🇱 · Jim Drachenberg (7)🇺🇸 · Dipangkar Dutta (8)🇺🇸 · Francesca Ercolessi (9)🇮🇹 · Mark Gorenstein (10)🇺🇦 and 31 other authors
This report summarizes the presentations and discussions during the ISO-BREAK 25 Workshop ``Isospin symmetry violation: kaons and beyond'', which was held at Jan Kochanowski University in Kielce on October 23-25, 2025. We address the current status of the isospin-symmetry breaking discovered by NA61/SHINE in nucleus-nucleus collisions at the CERN SPS, its confirmation by other experiments and studies in \ee and deep inelastic scattering. In addition, we discuss the theoretical status as well as we outline experimental and theoretical priorities towards understanding this currently unexplained phenomenon.
Comments:
33 pages, 12 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.16005 [pdf]
2 citations

Affiliations

first authorsco-authorsvia INSPIRE