Nuclear Theory·nucl-th

Tuesday·February 24, 2026

16 papers—9 primary·7 cross-listed

01
[Submitted on 20 Feb 2026]
Two-pion exchange nucleon-nucleon potentials with Roper resonance excitation
Norbert Kaiser🇩🇪
Motivated by the recent paper arXiv:2602.11815 [nucl-th], we calculate in these notes the spectral functions (i.e. imaginary parts) of the NN-potentials as they arise from $2 π$ -exchange with single and double Roper resonance excitation. In contrast to the full one-loop calculation, the spectral functions of the isoscalar and isovector central and tensor potentials can be given in simple analytical form. The pertinent momentum-space potentials $V_{C} (q), W_{C} (q), V_{T} (q), W_{T} (q)$ are obtained via subtracted dispersion relations. This representation allows also to include a regulator function, that tames high-momentum components of the chiral $2 π$ -exchange. The calculation is extended to $2 π$ -exchange with combined $Δ (1232)$ -isobar and Roper resonance excitation.
Comments:
4 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.18664 [pdf]
1 citation
02
[Submitted on 21 Feb 2026]
Resolution-matched nuclear geometry and the nucleon-size ambiguity in relativistic heavy-ion collisions
Hao-jie Xu🇨🇳
Nuclear structure theory provides point-nucleon densities, whereas high-energy nuclear collisions probe nuclei through finite-resolution hadronic interactions. This resolution mismatch becomes a physical ambiguity when point densities are embedded in Monte Carlo initial-state models with a finite transverse nucleon profile. A parameter intended to describe the effective interaction range can then also reshape the nuclear surface, blurring the separation between nuclear structure and collision dynamics. I show that this ambiguity can largely account for the strong nucleon-width dependence of the $^{208}$ Pb+ $^{208}$ Pb hadronic cross section ( $σ_{AA}$ ) reported in recent Bayesian analyses. Fixing the folded density that enters the Glauber phase shift removes this ambiguity at the level of nuclear geometry. The corrected cross section becomes nearly insensitive to a Gaussian nucleon width and instead probes the nuclear surface. Within a two-component estimate for $^{208}$ Pb, the current experimental uncertainty of $σ_{AA}$ translates into a broad neutron-skin interval, $Δ r_{np} \in [0, 0.21]$ fm. These results reframe $σ_{AA}$ as a surface-sensitive bridge between point-nucleon nuclear structure and finite-resolution high-energy initial conditions, rather than as a standalone nucleon-size observable. This establishes resolution matching as a necessary step for using relativistic heavy-ion collisions as quantitative probes of nuclear structure.
Comments:
11 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2602.18683 [pdf]
2 citations
03
[Submitted on 22 Feb 2026]
Constraining the nuclear symmetry energy with electric dipole polarizability and neutron skin characteristics in \texorpdfstring{ $^{208} Pb$ }{208Pb} within antisymmetrized molecular dynamics
Dandan Niu · Xinyu Wang · Ying Cui · Qiang Zhao · Kai Zhao · Akira Ono · Yingxun Zhang
The electric dipole polarizability $α_{D}$ and the neutron-skin thickness $Δ R_{n p}$ of $^{208} Pb$ are two powerful and clean probes for constraining the symmetry energy at subsaturation densities. Within the framework of the antisymmetrized molecular dynamics (AMD) model, the width of the strength function and its dynamical origins are understood, and the $α_{D}$ and $Δ R_{n p}$ data favor effective interaction parameter sets with $S_{0} \approx 32$ -34 MeV and $L = 64$ -87 MeV. In addition, our calculations show that the sensitive densities of $α_{D}$ and $Δ R_{n p}$ range from 0.2 $ρ_{0}$ to 0.57 $ρ_{0}$ , and the corresponding values of the symmetry energy at the lower and upper ends of this sensitive density region are $S (0.2 ρ_{0}) = 10.18 \pm 1.10$ MeV and $S (0.57 ρ_{0}) = 22.31 \pm 1.32$ MeV.
Comments:
13 pages, 8 figures, accepted by Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2602.19039 [pdf]
PRC(2026)·1 citation
04
[Submitted on 22 Feb 2026]
Probing the structure of pygmy dipole resonance with its gamma decay
W.-L. Lv · Y.-F. Niu · G. Colò
The isospin properties and the collectivity of the pygmy dipole resonance (PDR) are long-standing open questions in nuclear structure studies. To answer these questions, the $γ$ -decay of PDR states in $^{208}$ Pb to the low-lying $2_{1}^{+}$ state is investigated using the Skyrme particle-vibration coupling (PVC) model. It is found that the $E 1$ $γ$ decay from the PDR states to the low-lying $2_{1}^{+}$ state is strongly suppressed compared to that from the isovector giant dipole resonance (IVGDR), which reveals the predominantly isoscalar character of PDR. A detailed decomposition of the decay diagrams of the amplitudes of the processes contributing to the decay demonstrates the non-negligible presence of the 1 particle-1 hole configurations coupled to the $2_{1}^{+}$ phonon in the PDR wave function. Furthermore, we give a quantitative way to identify the components of complex-configurations in the wave function, and it is found that such component in PDR is smaller than that in IVGDR and much smaller than that in isoscalar giant quadrupole resonance (ISGQR).
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.19052 [pdf]
PRC(2026)·1 citation
05
[Submitted on 22 Feb 2026]
Charmonium suppression in fixed target proton-nucleus collisions
Sourav Kanti Giri🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Biswarup Paul🇮🇳 · Santosh K. Das🇮🇳
In this article, we perform a systematic investigation of the cold nuclear matter (CNM) effects, operative on charmonium ( $J / ψ$ , $ψ (2 S)$ ) production, in fixed target proton-nucleus (p+A) collisions. Influence on charmonium production cross section due to the interplay of three different plausible CNM effects namely the initial-state parton energy loss, nuclear shadowing, and final-state absorption of the resonant states, are evaluated in detail. The available data on charmonium production in fixed target p+A collision experiments from SPS, Fermilab and HERA-B are examined for this purpose. The beam energy dependence of the observed $J / ψ$ production patterns are utilized to anticipate level of "normal" absorption in the upcoming proton induced collisions by the NA60+ experiment at CERN SPS and the CBM experiment at FAIR SIS100 accelerator facilities.
Comments:
22 pages, 20 figures. Version accepted for publication in EPJC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2602.19072 [pdf]
EPJC(2026)·1 citation
06
[Submitted on 22 Feb 2026]
Nuclear Pasta and Crustal Quasi-Periodic Oscillations in Neutron Star
Vishal Parmar · Ignazio Bombaci
We investigate the impact of nuclear pasta on crustal structure and torsional oscillations using a Bayesian ensemble of unified neutron-star equations of state based on relativistic mean-field models constrained by nuclear experiments, empirical saturation properties, chiral effective field theory, and multimessenger observations. For each posterior sample, we compute the pasta sequence within a compressible liquid-drop model and quantify the onset density, thickness, and mass fraction of the pasta layers. We show that the appearance and extent of nuclear pasta are primarily controlled by the symmetry-energy slope parameter $L$ . While spherical and rod-like pasta configurations are present for all equations of state, only a small fraction of the posterior supports slab, tube, or bubble geometries. The transition from spherical nuclei to rods is tightly constrained to occur at a density of $ρ_{sr} = 0.058 8_{- 0.0065}^{+ 0.0045} f m^{- 3}$ . We further predict that the nuclear pasta layer occupies a relative radial thickness of $Δ R_{pasta} /Δ R_{c} = 0.14 0_{- 0.036}^{+ 0.025}$ and contributes a relative mass fraction of $Δ M_{pasta} /Δ M_{c} = 0.47 5_{- 0.113}^{+ 0.071}$ . Using the resulting crust models, we present the first quasi-periodic oscillations (QPOs) analysis based on a Bayesian posterior ensemble of neutron-star equations of state and systematically assess their compatibility with observed low-frequency quasi-periodic oscillations. We find that the predicted QPO frequencies are strongly correlated with the curvature of the symmetry energy evaluated at sub-saturation density, $K_{sym} (ρ_{0} /2)$ , and that uncertainties in the equation of state translate into a range of angular indices $ℓ$ consistent with the observed frequencies.
Comments:
12 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2602.19125 [pdf]
PRD(2026)·2 citations
07
[Submitted on 23 Feb 2026]
Microscopic Optical Potential from Brueckner-Hartree-Fock Theory
Miao Qi · Li-Li Chen · Li-Gang Cao · Feng-Shou Zhang · Xin-Le Shang · Wei Zuo · U. Lombardo
Modern Brueckner-Hartree-Fock (BHF) calculations are very successful in describing various properties of symmetric and asymmetric nuclear matter. Within BHF theory a microscopic optical potential (MOP) for nucleon-nucleus scattering is developed. First, we parametrize the energy and density dependence of complex optical potentials in nuclear matter based on BHF calculations and then we construct the MOP for finite nuclei with the local density approximation extended to include the finite-range effects. The density distribution and the spin-orbit contribution are calculated from the Hartree-Fock (HF) approximation with LNS5 Skyrme interaction, the latter being constrained by the BHF results. The central real and imaginary potentials turn out to be quantitatively consistent with the phenomenological global Koning-Delaroche (KD) potentials. The performance of MOP is evaluated by considering neutron/proton scattering on $^{40, 48}$ Ca. The elastic scattering differential cross sections, analyzing powers and total/reaction cross sections are analyzed in the energy below 200 MeV. A good agreement between the theoretical results and the measurements is achieved. Since our results are presented in the analytic forms, they can thus be used easily in the analysis of the experimental data of the nucleon scattering on exotic nuclei.
Comments:
14 pages, 8 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.19465 [pdf]
PRC(2026)·0 citations
08
[Submitted on 23 Feb 2026]
A Boson exchange approach for Helium Burning Stars
Theodoros Depastas · Aldo Bonasera
Helium burning plays a key role in the hierarchy of stellar nucleosynthesis and evolution, as the archetype of a bosonic 3-body system. Here, we examine the kinetic and nuclear aspects of the 3 $α$ reaction, under the auspices of the Thomas-Efimov theorem. Due to the 92.08 keV ground state of $^{8}$ Be, multiple $α$ -cluster resonances appear especially at the lowest temperature (Thomas State), while with increasing temperature the system is dominated by the Hoyle/Efimov state. We extend our previous methodology for the sequential channel to describe the direct mechanism, that results in an equilateral geometry similar to the Thomas state. This is accomplished by developing a general approach to the N-body scattering, via successive particle-exchanging 2-body collisions, which eliminates long range Coulomb complications, in a similar manner to the Thomas-Efimov mechanism. We furthermore, discuss the e $^{+}$ e $^{-}$ decay of the compound state with a perturbation based methodology. Due to the symmetry of the system and the resulting reaction rates, we favor the E0 decay scheme over the E2. The E0 reaction rates obey all the available astrophysical and nuclear constraints and are compared to theoretical data from the literature, whose limitations are discussed. Our extended methodology provides a physically sound description of the debated low temperature region.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.19515 [pdf]
PLB(2026)·0 citations
09
[Submitted on 23 Feb 2026]
Investigation of the $K^{-} pp$ Bound State via the $ K^{-} + {}^{3}\mathrm{He} $ Reaction
Sajjad Marri🇮🇷 · Ahmad Naderi Beni🇮🇷
Using the four-body Alt-Grassberger-Sandhas (AGS) equations for the $ K^{-}ppn $ system, we investigate the possible formation of a $ K^{-}pp $ quasi-bound state through the low-energy $ K^{-} + {}^{3}\mathrm{He} $ reaction. The neutron missing mass spectrum in the final state was calculated for different models of the $ \bar{K}N $ interaction. The results indicate that, irrespective of the specific nature of the $ \Lambda(1405) $ structure or the details of the $ \bar{K}N $ interaction model, a signal corresponding to the $ K^{-}pp $ quasi-bound state could appear in the $ \pi \Sigma p $ mass spectrum. This supports the feasibility of observing the $ K^{-}pp $ cluster in low-energy kaon-induced reactions on helium-3.
Comments:
11 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.19716 [pdf]
EPJA(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE