Nuclear Theory·nucl-th

Thursday·February 5, 2026

8 papers—5 primary·3 cross-listed

01
[Submitted on 4 Feb 2026]
Mapping Nuclear Deformation with Differential Radial Flow in Heavy-Ion Collisions
Jie Zhu🇨🇳 · Xiang-Yu Wu🇨🇦 · Guang-You Qin🇨🇳
In relativistic heavy-ion collisions, the radial flow of the fireball, usually characterized by transverse momentum spectra of final-state particles, encodes essential information about the hot and dense nuclear matter created in the collisions. However, the response of radial flow, including its $p_{T}$ -differential structure $v_{0} (p_{T})$ and longitudinal fluctuations $v_{0} (η)$ , to intrinsic nuclear deformation remains unexplored. Using realistic $(3 + 1)$ -dimensional viscous hydrodynamic calculations with Trento-3D initial conditions, we investigate how nuclear deformation affects the differential radial flow. We observe a clear, positive correlation between quadrupole deformation $β_{2}$ and radial flow: both magnitudes of $v_{0}$ and $v_{0} (p_{T})$ are enhanced in central collisions when $β_{2}$ is increased. In contrast, the Pearson coefficient $ρ (n (p_{T}), [p_{T}])$ exhibits a universal step-like behavior across all collision systems and centralities. Further analysis of longitudinal decorrelation of radial flow reveals a rich structure: in central collisions, large $β_{2}$ tends to suppress the decorrelation, whereas hexadecapole deformation $β_{4}$ tends to enhance it. Such decorrelation effect increases toward peripheral collisions. Our results demonstrate that precise measurements of radial flow, spanning transverse momentum and longitudinal dependences, can provide powerful, complementary constraints on nuclear deformation in high-energy nucleus-nucleus collisions.
Comments:
12 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2602.04148 [pdf]
2 citations
02
[Submitted on 4 Feb 2026]
Hyperon single-particle potentials in nuclear matter based on baryon-baryon interactions derived within chiral effective field theory
Asanosuke Jinno🇯🇵 · Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪
An analysis of the Lambda and Sigma single-particle potentials is presented, based on YN interactions derived within chiral effective field theory up to next-to-next-to-leading order (N $^{2}$ LO). The self-consistent Brueckner-Hartree-Fock framework is employed within the continuous choice for the single-particle potential. The result for the Lambda single-particle potential is comparable to the ones obtained with previous chiral YN interactions up to next-to-leading order (NLO). The Sigma single-particle potential is found weakly attractive, in contrast to earlier weakly repulsive results, reflecting new constraints from the recent J-PARC E40 data on $Σ^{+} p$ scattering. An estimate of the theoretical uncertainty of the single-particle potentials is provided.
Comments:
6 pages, 4 figures, 2 tables, conference proceeding of The 15th International Conference on Hypernuclear and Strange Particle Physics (HYP2025)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.04281 [pdf]
0 citations
03
[Submitted on 4 Feb 2026]
Neutron Dark Decay and Exotic Compact Objects
M. Vikiaris🇬🇷 · V. Petousis🇨🇿 · M. Veselsky🇨🇿 · Ch.C. Moustakidis🇬🇷
Recent measurements of the compact star XTE J1814-338, with a mass of $M = 1. 2_{- 0.05}^{+ 0.05} M_{⊙}$ and a radius of $R = 7_{- 0.4}^{+ 0.4} Km$ alongside those of HESS J1731-347, which has a mass of $M = 0.7 7_{- 0.17}^{+ 0.20} M_{⊙}$ and a radius of $R = 10. 4_{- 0.78}^{+ 0.86} Km$ , provide compelling evidence for the potential existence of exotic matter in neutron star cores. These observations offer important insights into the equation of state of dense nuclear matter. Recently, Fornal and Grinstein, in order to overcame the discrepancy between the neutron lifetime measured in beam and bottle experiments, proposed the existence of neutron dark decay. In the present work, an effort is made to connect the interpretation of the above exotic compact objects with the possible existence of dark particles, assumed to be products of neutron dark decay. Our hypothesis offers an advantage over comparable proposals, as the coexistence of dark matter and hadronic matter within neutron stars emerges from an intrinsic mechanism, thereby obviating the need to invoke external merger-related processes. It is still unclear to what extent the proposed dark decay of the neutron is affected by the extreme environment within neutron stars. Within this framework, we examined the case in which a mechanism suppressing the dark neutron decay becomes operative at densities few times above nuclear saturation density. We found that the proposed alternative explanation accommodates the simultaneous existence of neutron dark decay while consistently predicting both the two solar mass limit and the presence of compact objects with subsolar masses.
Comments:
11 pages, 5 figures, any comment is welcome
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2602.04477 [pdf]
PRD(2026)·0 citations
04
[Submitted on 4 Feb 2026]
Exterior complex scaling enables physics-informed neural networks for quantum scattering
Jin Lei
Physics-informed neural networks (PINNs) have emerged as a powerful tool for solving differential equations, yet their application to nuclear scattering has been hindered by the oscillatory, non-decaying nature of scattering wave functions. In this work, I demonstrate that exterior complex scaling (ECS) transforms scattering boundary conditions into exponentially decaying waves suitable for neural network solutions, enabling PINNs to solve nuclear reaction problems for the first time. I develop a driven-equation formulation where the source term is confined to the real axis, avoiding the need to analytically continue nuclear potentials into the complex plane. The method is validated on nucleon-nucleus scattering (n+ $^{40}$ Ca at $E_{lab} = 20$ ~MeV) with 21 partial waves, achieving phase shift accuracy of $Δ δ ≲ 0. 1^{\circ}$ for the strongly absorbed channels ( $ℓ \leq 4$ ) and $Δ δ \leq 0.6 0^{\circ}$ for all channels up to $ℓ = 10$ , when compared to conventional solvers. I further demonstrate the approach on heavy-ion scattering ( $^{6}$ Li+ $^{208}$ Pb at 40~MeV) with 41 partial waves and strong Coulomb effects, where an auto-adaptive anchor warm-down for weak-source channels yields a mean S-matrix accuracy of $∣Δ∣ S_{ℓ} ∣∣ \approx 3 \times 1 0^{- 3}$ across the full angular momentum range, including the absorption-to-transparency transition region. This work establishes the foundation for extending PINNs to inverse problems where end-to-end differentiability enables direct fitting of optical potential parameters, coupled-channel reactions, and few-body scattering where traditional grid methods face exponential scaling.
Subjects:
Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2602.04553 [pdf]
PRC(2026)·4 citations
05
[Submitted on 4 Feb 2026]
A Hierarchical Bayesian Analysis of Neutron-Skin Thicknesses and Implications for the Symmetry-Energy Slope
Adrian Azizi · Carlos A. Bertulani · Carlos Davila
Neutron-skin thicknesses provide a sensitive probe of the isovector sector of the nuclear equation of state and its density dependence, commonly characterized by the symmetry-energy slope parameter L. A wide variety of experimental and observational methods have been used to extract neutron skins, ranging from hadronic and electromagnetic probes of finite nuclei to inferences from neutron-star observations. Each approach carries distinct theoretical and systematic uncertainties, complicating global interpretations and obscuring genuine physical trends. In this work we present a hierarchical Bayesian framework for the statistically consistent synthesis of heterogeneous neutron-skin constraints. The neutron-skin thickness is modeled as a smooth latent function of isospin asymmetry and nuclear size, while method-dependent bias parameters and intrinsic nuisance widths are introduced to account for unmodeled experimental and theoretical systematics. Focusing on the tin isotopes, we infer probabilistic neutron-skin trends from 100Sn to 140Sn, finding minimal uncertainties near stability and increasing uncertainties toward the proton-rich and neutron-rich extremes. We assess the consistency of nuclear energy-density functionals and obtain conditional constraints on the symmetry-energy parameters. The resulting posterior exhibits a pronounced compression of the symmetry-energy slope parameter L, reflecting the dominant sensitivity of neutron skins to sub-saturation symmetry pressure. We demonstrate that our hierarchical Bayesian framework provides robust and transparent constraints on the sub-saturation isovector sector of the nuclear equation of state.
Comments:
10 pages, 4 figures, Phys. Rev. C, to be published
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2602.04794 [pdf]
PRC(2026)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Mapping Nuclear Deformation with Differential Radial Flow in Heavy-Ion Collisions

Hyperon single-particle potentials in nuclear matter based on baryon-baryon interactions derived within chiral effective field theory

Neutron Dark Decay and Exotic Compact Objects

Exterior complex scaling enables physics-informed neural networks for quantum scattering

A Hierarchical Bayesian Analysis of Neutron-Skin Thicknesses and Implications for the Symmetry-Energy Slope

Affiliations