Nuclear Theory·nucl-th

Monday·June 23, 2025

20 papers—6 primary·14 cross-listed

01
Phase-space excluded-volume approach for light clusters in nuclear medium
Rui Wang🇮🇹 · Zhen Zhang🇨🇳 · Stefano Burrello🇮🇹 · Maria Colonna🇮🇹 · Edoardo G. Lanza🇮🇹
A phase-space excluded-volume approach is developed to investigate the in-medium properties of light clusters in nuclear matter. In this approach, light clusters can exist only if the total nucleon phase-space occupation of the surrounding nuclear medium -- including explicit contributions from light clusters -- is sufficiently low. The distribution functions of nucleons and light clusters are determined self-consistently by accounting for the interplay between in-medium effects and thermodynamic properties. By employing standard Skyrme energy-density functionals to model the nuclear mean-field potential, the approach enables the evaluation of the Mott momentum and the fraction of light clusters in nuclear matter. Furthermore, it can be readily integrated into dynamical models, to study in-medium effects on light clusters, based on measured yields in heavy-ion collisions.
nucl-thPRC(2026)·4 citations
02
np spin correlations in the deuteron ground state
Ashutosh Singh · Ankit Kumar Das · Ankit Kumar · P. Arumugam
The deuteron is the simplest atomic nucleus made of two particles - a proton and a neutron. In this work, we study how their spins are quantum entangled with each other. We study two cases: when the deuteron is in a fixed projection of total angular momentum, and when it exists in a superposition of all projections. Our findings show that the spins are most entangled when the total projection is zero, and that strong entanglement still exists even when all spin states are superposed.
nucl-thquant-ph2 citations
03
Chiral Invariant Mass Constraints from HESS J1731 347 in an Extended Parity Doublet Model with Isovector Scalar Meson
Yuk-Kei Kong🇯🇵 · Bikai Gao🇯🇵 · Masayasu Harada🇯🇵
The recent discovery of a central compact object (CCO) within the supernova remnant HESS J1731-347, with mass $0.7 7_{- 0.17}^{+ 0.20} M_{⊙}$ and radius $10. 4_{- 0.78}^{+ 0.86}$ km is the lightest and smallest compact object ever observed. We identify it as an ultra-light Neutron star (NS) and constrain the chiral invariant mass of nucleon $m_{0}$ from the observational data of NS using an extended parity doublet model with including the isovector scalar meson $a_{0} (980)$ . We study the higher order asymmertic matter properties such as the symmetry incompressibility $K_{sy m}$ and the symmetry skewness $Q_{sy m}$ in the presence of $a_{0}$ meson. We find that $K_{sy m}$ and $Q_{sy m}$ is sensitive to the chiral invariant mass of nucleon $m_{0}$ in the presence of $a_{0}$ meson. We show that the equation of state in the present model satisfies all observational constraints within $2 σ$ credible region including the HESS J1731-347 observation, as well as the constraint from $K_{sy m}$ when $740 MeV ≲ m_{0} ≲ 860 MeV$ for $L_{0} =$ 57.7 MeV. Yet, the $1 σ$ constraint from neutron stars appears to be not fully compatible with the constraint from $K_{sy m}$ from the present model.
nucl-thastro-ph.HEastro-ph.SRhep-phUniverse(2025)·12 citations
04
Photon Emission from Nucleon-Nucleon Bremsstrahlung in Fermi-energy Heavy-Ion Collisions
Thomas Onyango🇺🇸 · Ralf Rapp🇺🇸
The emission of direct (hard and thermal) photons from nucleon-nucleon Bremsstrahlung in heavy-ion collisions at Fermi energies is analyzed. We utilize a photon emission rate based on a quantum-field-theoretical model together with nucleon distribution functions extracted from a coarse-graining method of transport model simulations. The latter accounts for off-equilibrium effects during the early stages of nuclear collisions primarily occurring in the beam direction while the transverse-momentum distributions are amenable to a thermal description. With this setup, we quantify the contributions from first-chance nucleon-nucleon collisions and the subsequent transition to a thermal source to the photon energy spectrum measured from Ca-Ca collisions at 35 A $\cdot$ MeV bombarding energy. We find that most of the hard photons are produced in the initial stages of heavy-ion collisions from primordial collisions where nucleons move with the initial collective nuclear motion while the emission from the later stages plays a sub-dominant role. We compare our calculations to experimental measurements of a differential photon-energy spectrum from a collision system of similar size and beam energy, thereby including acceptance cuts as applied in the detectors.
nucl-th0 citations
05
Impact of $Ξ$ -Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars
Shi Yuan Ding🇨🇳 · Xiang Dong Sun🇨🇳 · Bao Yuan Sun🇨🇳 · Ang Li🇨🇳
Significant uncertainties persist in describing the equation of state and internal structure of hyperon stars due to the limited understanding of the mechanisms underlying hyperon interactions. Constraining the interaction parameter space through a combination of the latest astronomical observations and hypernuclear physics experiments is therefore essential. In this study, we incorporate experimental constraints from $Ξ$ hypernuclear physics on top of $Λ$ hyperons considered in \citet{Sun2023APJ942.55}. Specifically, based on updated measurements of hyperon separation energies from $Ξ$ hypernuclear experiments, sets of $Ξ N$ effective interactions are constructed and a linear correlation between their scalar ( $σ$ ) and vector ( $ω$ ) coupling strength ratios is proposed as a constraint derived from $Ξ$ hypernuclear physics. Together with experimental correlations and astronomical observational data, four types of analyses are performed to constrain hyperon-nucleon interactions and the properties of hyperon stars. Compared to the vector $ω$ meson-hyperon coupling, the introduction of linear correlations in hypernuclear physics imposes a more substantial constraint on the scalar $σ$ meson-hyperon coupling, significantly enhancing its coupling strength and thereby ensuring the stiffness of the equation of state, highlighting the crucial role of hypernuclear studies in solving the hyperon puzzle problem. Consequently, a maximum mass of around $2 M_{⊙}$ can be achieved with all five interactions considered in this study under the combined constraints from astronomical observations and nuclear physics. With more reliably estimated hyperon-nucleon contributions, the uncertainties in both the fractions and the threshold densities at which hyperons appear inside neutron stars are notably reduced, along with those in the mass-radius predictions.
nucl-thastro-ph.HEPRD(2025)·4 citations
06
Impact of pion tensor force on alpha clustering in $^{20}$ Ne
Zhao Jing Chen · Bao Yuan Sun
The nuclear clustering, as a quantum phase transition phenomenon governed by strong interactions, exhibits characteristics that are highly sensitive to the specific features of nuclear forces. Here, we examine how nuclear deformation and tensor forces influence $α$ -cluster formation in light nuclei. The axially deformed relativistic Hartree-Fock-Bogoliubov model is utilized to investigate the clustering structure of the $^{20}$ Ne nucleus, at both the ground state and the excited state with a superdeformed prolate. The nuclear binding energies and the canonical single particle levels are obtained at different quadruple deformation, and the role of tensor force embedded in the Fock diagram of $π$ -pseudovector ( $π$ -PV) coupling is revealed. It is shown that the level branches from the degenerated spherical orbits at the deformed prolate case are enlarged due to the extra contribution from pion-exchanged tensor force. Correspondingly, the excitation energy in this superdeformed prolate state is reduced due to the noncentral tensor interaction, leading to a predicted value which is much closer to the referred threshold for the $2 α$ decay mode of $^{20}$ Ne. Possible $α$ -clustering configurations in $^{20}$ Ne are then characterized by examining the nucleonic localization function. Although the contribution to the ground state is relatively small, the density profile and nucleonic localization are significantly changed by the pion tensor force for the superdeformed prolate excited state, as further evidenced by characterising the level mixing in the spherical basis components. The results reveal the extra role of the tensor force, correlated to the evolved single-particle levels with nuclear deformation, in the formation and stability of nuclear clustering.
nucl-thPLB(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Phase-space excluded-volume approach for light clusters in nuclear medium

np spin correlations in the deuteron ground state

Chiral Invariant Mass Constraints from HESS J1731 347 in an Extended Parity Doublet Model with Isovector Scalar Meson

Photon Emission from Nucleon-Nucleon Bremsstrahlung in Fermi-energy Heavy-Ion Collisions

Impact of Ξ-Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars

Impact of pion tensor force on alpha clustering in 20Ne

Affiliations

Impact of $Ξ$ -Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars

Impact of pion tensor force on alpha clustering in $^{20}$ Ne