Nuclear Theory·nucl-th

Tuesday·September 17, 2024

18 papers—9 primary·9 cross-listed

01
[Submitted on 14 Sept 2024]
Multiple-models prediction for light neutron-rich isotopes cross section by $Q_{g}$ systematics in $^{40}$ Ar projectile fragmentation reactions
X. B. Wei · H. L. Wei · C. W. Ma · C. Y. Qiao · Y. F. Guo · J. Pu · K. X. Cheng · Y. T. Wang · Z. X. Wang · T. R. Zhou · D. Peng · S. T. Wang and 11 other authors
Precise predictions for nuclei near drip lines are crucial for experiments in new generation of rare isotope facilities. A multi-models investigation of the $Q_{g}$ systematics for fragments production cross sections, with $Q_{g}$ defined as the difference of mass excess (ME) between the projectile ( $Z_{p}, A_{p}$ ) and the fragment ( $Z_{f}, A_{f}$ ) nuclei $Q_{g} = M E (Z_{p}, A_{p}) - M E (Z_{f}, A_{f})$ , has been performed to verify the model prediction abilities for light neutron-rich isotopes in measured $^{40}$ Ar + $^{9}$ Be projectile fragmentation reactions from 57 $A$ MeV to 1 $A$ GeV. The models used are the FRACS parametrizations and the newly developed Bayesian neural networks (BNN) model. %method The results show that FRACS, BNN, and $Q_{g}$ extrapolations are generally consistent, except for fragments near the nuclear mass of the projectile. Additionally, both measured data and model extrapolations provide evidence for a shell closure at $N =$ 16 in fluorine and neon, as well as the disappearance of the traditional magic number $N =$ 20 in neon, sodium and magnesium.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2409.09367 [pdf]
0 citations
02
[Submitted on 14 Sept 2024]
Pion-nucleon scattering with decuplet contribution in heavy baryon SU(3) chiral perturbation theory
Jing Ou-Yang🇨🇳 · Bo-Lin Huang🇨🇳
We calculate the complete $T$ matrices with decuplet contributions for pion-nucleon scattering to order $O (ϵ^{3})$ in heavy baryon SU(3) chiral perturbation theory. The baryon mass in the chiral limit $M_{0}$ and the low-energy constants are determined by fitting to phase shifts of $π N$ , the experimental octet-baryon masses, and the value of $σ_{π N}$ simultaneously. By using these constants, we obtain the $K N$ $σ$ terms, $σ_{K N}^{(1)} = (375.07 \pm 33.02)$ MeV and $σ_{K N}^{(2)} = (275.32 \pm 32.24)$ MeV, with the errors being only statistical. An excellent description of the phase shifts is obtained for all partial waves. We also present results for scattering lengths and scattering volumes. In addition, the convergence of the approach is also discussed.
Comments:
29 pages, 6 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2409.09388 [pdf]
PRD(2024)·4 citations
03
[Submitted on 14 Sept 2024]
Effect of Magnetic Fields on Urca Rates in Neutron Star Mergers
Pranjal Tambe🇮🇳 · Debarati Chatterjee🇮🇳 · Mark Alford🇺🇸 · Alexander Haber🇺🇸
Isospin-equilibrating weak processes, called ``Urca" processes, are of fundamental importance in astrophysical environments like (proto-)neutron stars, neutron star mergers, and supernovae. In these environments, matter can reach high temperatures of tens of MeVs and be subject to large magnetic fields. We thus investigate Urca rates at different temperatures and field strengths by performing the full temperature and magnetic-field dependent rate integrals for different equations of state. We find that the magnetic fields play an important role at temperatures of a few MeV, especially close to or below the direct Urca threshold, which is softened by the magnetic field. At higher temperatures, the effect of the magnetic fields can be overshadowed by the thermal effects. We observe that the magnetic field more strongly influences the neutron decay rates than the electron capture rates, leading to a shift in the flavor equilibrium.
Comments:
Replace with published version in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2409.09423 [pdf]
PRC(2025)·13 citations
04
[Submitted on 14 Sept 2024]
Ab initio calculation of the $^{3}$ He $(α, γ)^{7}$ Be astrophysical S factor with chiral two- and three-nucleon forces
M.C. Atkinson · K. Kravvaris · S. Quaglioni · P. Navrátil
The $^{3}$ He $(α, γ)^{7}$ Be radiative capture reaction plays a key role in the creation of elements in stars as well as in the production of solar neutrinos, the observation of which is one of the main tools to study the properties of our sun. Since accurate experimental measurements of this fusion cross section at solar energies are difficult due to the strong Coulomb repulsion between the reactants, the onus falls on theory to provide a robust means for extrapolating from the region where experimental data is available down to the desired astrophysical regime. We present the first microscopic calculations of $^{3}$ He $(α, γ)^{7}$ Be with explicit inclusion of three-nucleon forces. Our prediction of the astrophysical $S$ factor qualitatively agrees with experimental data. We further incorporate experimental bound-state and scattering information in our calculation to arrive at a more quantitative description. This process reveals that our current model lacks sufficient repulsion in the $1/ 2^{+}$ channel of our model space to simultaneously reproduce elastic-scattering data. This deficit suggests that $^{3}$ He $(α, γ)^{7}$ Be probes aspects of the nuclear force that are not currently well-constrained.
Comments:
7 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2409.09515 [pdf]
PLB(2025)·14 citations
05
[Submitted on 15 Sept 2024]
Fuzzy logic for reconstructing arbitrary moments of multiplicity distributions
Anar Rustamov🇩🇪
The Identity Method is a statistical technique developed to reconstruct moments of multiplicity distributions of particles produced in high-energy nuclear collisions. The method leverages principles from fuzzy logic, allowing for a more nuanced representation of particle identification by assigning degrees of membership to different particle types based on detector signals. In this contribution, a new framework, based on a multivariate moment generation function, is developed that allows the derivation of the formulas used in the Identity Method in a more robust way. Moreover, within the introduced framework, the Identity Method is easily extended to cope with arbitrarily higher-order moments. The techniques developed here offer significant potential for improving the accuracy of multiplicity distribution analyses in high-energy nuclear collisions. While the primary focus of the work presented is on applications in high-energy particle and nuclear physics, it can also be applied in other areas where signal identification is probabilistic and data are noisy, such as in medical imaging, remote sensing, and various other fields of experimental science.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2409.09814 [pdf]
PRC(2024)·5 citations
06
[Submitted on 16 Sept 2024]
Quantum-mechanical description of angular motion of fission fragments at scission
T. M. Shneidman (1) · A. Rahmatinejad (1) · G. G. Adamian (1) · N. V. Antonenko (1) ( (1) Joint Institute for Nuclear Research, Dubna, Russia)
The quantum-mechanical description of the collective angular motion in a system of two touching fission fragments is proposed. The main peculiarities of excitation spectrum and the structure of the wave functions are investigated. As found, the angular motion approximately corresponds to independent vibrations of fragments around the pole-to-pole configuration. The model allows us to explain the experimentally observed lack of correlation between the angular momenta of fission fragments. Additionally the correlation between angular momentum and fragment mass is primarily linked to the change of fragments deformation. The saw-tooth behavior of angular momentum distribution with respect to the fragment mass is well explained.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2409.10114 [pdf]
PRC(2025)·6 citations
07
[Submitted on 16 Sept 2024]
Multiple rescattering effects in the hard knockout reaction $^{2} \mbox H (p, 2p) n$
A.B. Larionov🇷🇺
The interaction of a proton with a deuteron is the simplest nuclear reaction. However, it allows the study of precursors of nuclear medium effects such as initial-state/final-state interactions (ISI/FSI). In case of hard proton knockout, the deviation of ISI/FSI from the 'standard' values may carry a signal of color transparency. In this regard, it is important to define the 'standard' as precisely as possible. This work continues previous studies within the framework of the Generalized Eikonal Approximation (GEA). The focus is on processes where the participating protons experience multiple soft rescattering on the spectator neutron. It is shown that correct treatment of deviations of the trajectories of outgoing protons from the longitudinal direction leads to a significant modification of partial amplitudes with soft rescattering of two outgoing protons and non-vanishing amplitudes with rescattering of incoming and outgoing protons. The new treatment of multiple rescattering is important in kinematics with a forward spectator neutron.
Comments:
30 pages, 9 figures, model inputs section added, other minor corrections, version accepted in Eur. Phys. J. A
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2409.10260 [pdf]
EPJA(2025)·1 citation
08
[Submitted on 16 Sept 2024]
Ab initio calculations of anomalous seniority breaking in the $π g_{9/2}$ shell for the $N = 50$ isotones
Q. Yuan · B. S. Hu
We performed \textit{ab initio} valence-space in-medium similarity renormalization group (VS-IMSRG) calculations based on chiral two-nucleon and three-nucleon interactions to investigate the anomalous seniority breaking in the neutron number $N = 50$ isotones: $^{92}$ Mo, $^{94}$ Ru, $^{96}$ Pd, and $^{98}$ Cd. Our calculations well reproduced the measured low-lying spectra and electromagnetic $E 2$ transitions in these nuclei, supporting partial seniority conservation in the first $π g_{9/2}$ shell. Recent experiments have revealed that, compared to the symmetric patterns predicted under the conserved seniority symmetry, the $4_{1}^{+} \to 2_{1}^{+}$ $E 2$ transition strength in $^{94}$ Ru is significantly enhanced and that in $^{96}$ Pd is suppressed. In contrast, the $6_{1}^{+} \to 4_{1}^{+}$ and $8_{1}^{+} \to 6_{1}^{+}$ transitions exhibit the opposite trend. We found that this anomalous asymmetry is sensitive to subtle seniority breaking effects, providing a stringent test for state-of-the-art nucleon-nucleon interactions and nuclear models. We analyzed the anomalous asymmetry using VS-IMSRG calculations across various valence spaces. Our \textit{ab initio} results suggest that core excitations of both proton and neutron across the $Z = 50$ shell are ascribed to the observed anomalous seniority breaking in the $N = 50$ isotones.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2409.10342 [pdf]
PLB(2024)·9 citations
09
[Submitted on 16 Sept 2024]
Lévy walk of pions in heavy-ion collisions
Dániel Kincses🇭🇺 · Márton Nagy🇭🇺 · Máté Csanád🇭🇺
The process of Lévy walk, i.e., movement patterns described by heavy-tailed random walks, plays a role in various phenomena, from chemical and microbiological systems through marine predators to climate change. Recent experiments have suggested that this phenomenon also appears in heavy-ion collisions. However, the theoretical interpretation supporting such findings is still debated. In high-energy collisions of heavy nuclei, the strongly interacting Quark Gluon Plasma is created, which, similarly to the early Universe, undergoes a rapid expansion and transition back to hadronic matter. In the subsequent expanding hadron gas, particles interact until kinetic freeze-out, when their momenta stop changing, and they freely transition toward the detectors. Measuring spatial freeze-out distributions is a crucial tool in understanding the dynamics of the created matter and the interactions among its constituents. In this paper, we introduce a three-dimensional analysis of the spatial freeze-out distribution of pions (the most abundant particles in such collisions). Utilising Monte-Carlo simulations of high-energy collisions, we show that the chain of processes ending in a final state pion has a step length distribution leading to Lévy-stable distributions. Subsequently, we show that simulated pion freeze-out distributions indeed exhibit heavy tails and can be described by a three-dimensional elliptically contoured symmetric Lévy-stable distribution.
Comments:
23 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2409.10373 [pdf]
Commun.Phys.(2025)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE