Nuclear Theory·nucl-th

Monday·February 26, 2024

9 papers—8 primary·1 cross-listed

01
[Submitted on 22 Feb 2024]
Pairing enhancement through the photography of the intermediate nucleus spectrum in a two-nucleon transfer process
G. Singh
While forming an ( $A$ +2) nucleus from a nucleus $A$ via a two-neutron transfer reaction, the constructive interference of the many possible reaction channels favors significant pairing enhancement through the continuum of the intermediate ( $A$ +1) nucleus [Phys. Lett. B \textbf{834} 137413 (2022)]. I analyse this situation in more generality, from the point of view of a varying pairing field and different continua leading to the formation of ( $A$ +2) nucleus. I consider $^{6}$ He and $^{22}$ C, described as housing two-neutrons in orbitals of $^{5}$ He and $^{21}$ C, respectively. The different possible situations manifest that the continuum correlations are extremely crucial to the extension of the pairing enhancement observed in the system.
Comments:
11 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.14964 [pdf]
EPJA(2025)·1 citation
02
[Submitted on 22 Feb 2024]
Microscopic bell-shape nonlocality: the case of proton scattering off $^{40}$ Ca at 200 MeV
G. Blanchon🇫🇷 · H. F. Arellano🇨🇱
This work is part of an ongoing effort to build microscopically-driven nonlocal optical potentials easily tracktable in scattering codes. Based on the separable ` $J v H$ ' structure proposed recently \cite{arellano_22}, where the potential can be cast as the product of a radial and nonlocality form factors, we investigate its angular dependence in momentum space. We find that scattering observables have a weak angular dependence between the momentum transfer { $q = k - k^{'}$ }, and { $K = (k + k^{'}) /2$ }. The study is focussed on proton elastic scattering off $^{40}$ Ca at 200 MeV, where the $J v H$ structure is found to be inadequate. We conclude that any improvement of the $J v H$ structure of the potential can be made to the lowest order in multipole expansions in $K q -$ representation of the potential.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.15009 [pdf]
EPJ Web Conf.(2024)·1 citation
03
[Submitted on 23 Feb 2024]
Gallagher-Moszkowski splitting in deformed odd-odd nuclei within a microscopic approach
Ludovic Bonneau🇫🇷 · Nathanael Kontowicz🇫🇷 · Johann Bartel🇫🇷 · Herve Molique🇫🇷 · Meng Hock Koh🇲🇾 · Nikolay Minkov🇧🇬
Low-lying bandhead states in axially prolate deformed odd-odd nuclei have long been described essentially within the rotor+two-quasiparticle picture. This approach allows one to explain the appearance of so-called Gallagher-Moszkowski doublets of bandheads with $K = Ω_{n} \pm Ω_{p}$ , sum and difference of neutron and proton angular momentum projections on the symmetry axis. According to an empirical rule stated by Gallagher and Moszkowski the spin-aligned configuration lies lower in energy than the spin-anti-aligned configuration. A recent study by Robledo, Bernard and Bertsch in Phys. Rev. C 89, 021303(R) (2014) within the Gogny energy-density functional with selfconsistent blocking of the unpaired nucleons showed that calculations fail to reproduce this rule in about half of the cases and points to the density-dependent term of the functional as responsible of this failure. In this paper we aim at pushing further this analysis to exhibit the mechanism underlying the energy splitting in a Gallagher-Moszkowski doublet. We work in the framework of the Skyrme energy-density functional approach, including BCS pairing correlations with selfconsistent blocking. We use the SIII parametrization with time-odd terms and seniority pairing matrix elements extending a previous study of K-isomeric states in even-even nuclei [Phys. Rev. C 105, 044329 (2022)]. We find that the energy splitting results from a competition between the spin-spin, density-dependent and current-current terms of the Skyrme energy-density functional. In doublets where the larger K value is lower in energy the Gallagher-Moszkowski rule is always satisfied by the SIII Skyrme energy-density functional. In doublets, on the contrary, where the smaller K value lies lower, the energy splittings are calculated to be rather small and often a disagreement with the Gallagher-Moszkowski rule occurs.
Comments:
To be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.15201 [pdf]
PRC(2024)·3 citations
04
[Submitted on 23 Feb 2024]
Distinguishing fission-like events from deep-inelastic collisions
Hong Yao · Cheng Li · Houbing Zhou · Ning Wang
We propose two functions to distinguish fission-like events from quasi-elastic (QE) scattering and deep inelastic collisions (DIC), for a better analysis of the measured mass-total kinetic energy distributions of binary fragments formed in fusion-fission reactions. We note that the ratio of capture to DIC events evidently decreases with the decreasing of the depth of the capture pocket predicted from the Skyrme energy density functional, with which the capture pocket could be extracted from the measured mass-energy distributions. Together with the improved quantum molecular dynamics simulations, in which the typical contact time of the reaction partners is smaller than 200 fm/c for QE and is larger than 600 fm/c for fission-like events, we find that the ratio of capture to touching cross section systematically increases with the pocket depth.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2402.15224 [pdf]
PRC(2024)·6 citations
05
[Submitted on 23 Feb 2024]
Assessing the Impact of Nuclear Mass Models on the Prediction of Synthesis Cross Sections for Superheavy Elements
Chang Geng · Peng-Hui Chen · Fei Niu · Zu-Xing Yang · Xiang-Hua Zeng · Zhao-Qing Feng
Within the framework of the dinuclear system model, this study delves into the impact of various nuclear mass models on evaluating the fusion probability of superheavy nuclei. Nuclear mass models, as crucial inputs to the DNS model, exhibit slight variations in binding energy, quadrupole deformation, and extrapolation ability; these subtle differences can significantly influence the model's outcomes. Specifically, the study finds that nuclear mass plays a pivotal role in determining fusion probability, and Q-value. By numerically solving a set of master equations, the study examines how binding energies from different mass models affect the fusion probability of colliding nuclei, taking the example of $^{48}$ Ca + $^{243}$ Am $\to$ $^{291}$ Mc. A careful analysis of the potential energy surface (PES) reveals that the inner fusion barriers lead to variations in fusion probabilities. Importantly, the study demonstrates that the synthesis cross sections of superheavy nuclei calculated using different nuclear mass models align well with experimental data, falling within an error range of one order of magnitude. This finding underscores the reliability of our model predictions. Looking ahead, the study utilizes five distinct nuclear mass models to predict the synthesis cross sections of superheavy elements 119 and 120, along with their associated uncertainties. These predictions offer valuable insights into the feasibility of synthesizing these elusive elements and pave the way for future experimental explorations.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.15304 [pdf]
PRC(2024)·6 citations
06
[Submitted on 23 Feb 2024]
Perturbative computations of neutron-proton scattering observables using renormalization-group invariant $χ$ EFT up to N $^{3}$ LO
Oliver Thim · Andreas Ekström · Christian Forssén
We predict neutron-proton scattering cross-sections and polarization observables up to next-to-next-to-next-to leading order in a renormalization-group invariant description of the strong nucleon-nucleon interaction. Low-energy constants are calibrated to phase shifts, sub-leading corrections are computed in distorted-wave perturbation theory, and we employ momentum-cutoff values 500 and 2500 MeV. We find a steady order-by-order convergence and realistic descriptions of scattering observables up to a laboratory scattering energy of approximately 100 MeV. We also compare perturbative and non-perturbative calculations for phase shifts and cross sections and quantify how unitarity is gradually restored at higher orders. The perturbative approach offers an important diagnostic tool for any power counting and our results suggest that the breakdown scale in chiral effective field theory might be significantly lower than estimates obtained in non-perturbative calculations.
Comments:
18 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.15325 [pdf]
PRC(2024)·14 citations
07
[Submitted on 23 Feb 2024]
Worldline Monte Carlo method for few body nuclear physics
Shailesh Chandrasekharan (1)🇨🇳 · Son T. Nguyen (1 and 2)🇨🇳 · Thomas R. Richardson (1 and 3) ((1) Duke University, (2) Washington and Lee University, (3) Institut für Kernphysik and PRISMA+ Cluster of Excellence, Johannes Gutenberg-Universität)🇨🇳
In this work we introduce a worldline based fermion Monte Carlo algorithm for studying few body quantum mechanics of self-interacting fermions in the Hamiltonian lattice formulation. Our motivation to construct the method comes from our interest in studying renormalization of chiral nuclear effective field theory with lattice regularization. In particular we wish to apply our method to compute the lattice spacing dependence of local lattice interactions as we take the continuum limit of the lattice theory. Our algorithm can compute matrix elements of the operator $exp (- β H)$ where $H$ is the lattice Hamiltonian and $β$ is a free real parameter. These elements help us compute deep bound states that are well separated from scattering states even at values of $β$ which are not very large. Computing these bound state energies accurately can help us study renormalization of the lattice theory. In addition to developing the algorithm, in this work we also introduce a finite volume renormalization scheme for the lattice Hamiltonian of the leading pionless effective field theory and show how it would work in the one and two body sectors.
Comments:
23 pages, 8 figures, 17 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
arXiv:
2402.15377 [pdf]
PRC(2024)·4 citations
08
[Submitted on 23 Feb 2024]
Extended Fayans energy density functional: optimization and analysis
Paul-Gerhard Reinhard · Jared O'Neal · Stefan M. Wild · Witold Nazarewicz
The Fayans energy density functional (EDF) has been very successful in describing global nuclear properties (binding energies, charge radii, and especially differences of radii) within nuclear density functional theory. In a recent study, supervised machine learning methods were used to calibrate the Fayans EDF. Building on this experience, in this work we explore the effect of adding isovector pairing terms, which are responsible for different proton and neutron pairing fields, by comparing a 13D model without the isovector pairing term against the extended 14D model. At the heart of the calibration is a carefully selected heterogeneous dataset of experimental observables representing ground-state properties of spherical even-even nuclei. To quantify the impact of the calibration dataset on model parameters and the importance of the new terms, we carry out advanced sensitivity and correlation analysis on both models. The extension to 14D improves the overall quality of the model by about 30%. The enhanced degrees of freedom of the 14D model reduce correlations between model parameters and enhance sensitivity.
Comments:
29-page article, 1-page notice
Subjects:
Nuclear Theory (nucl-th); math.OC (math.OC)
arXiv:
2402.15380 [pdf]
J.Phys.G(2024)·15 citations
09
[Submitted on 23 Feb 2024] (cross-list from hep-ph)
Functional renormalization group study of the quark-meson model with omega and rho vector mesons
Mohammed Osman🇨🇳 · Defu Hou🇨🇳 · Wentao Wang🇨🇳 · Hui Zhang🇨🇳
We employ the functional renormalization group flow equations to investigate the phase structure of the two-flavor quark-meson model in the presence of a finite isospin chemical potential, incorporating interactions with omega and rho vector mesons. For comparison, we also compute the phase diagram in the chiral limit using the mean-field approximation. Our findings demonstrate that omega and rho mesons affect the phase structure in markedly distinct ways, and the introduction of an isospin chemical potential leads to significant modifications in the phase boundaries and critical region. Increasing the isospin chemical potential lowers the tricritical points temperature, and tends to suppress the unphysical ``back-bending" of the FRG phase boundary at low temperature.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2402.15474 [pdf]
EPJC(2025)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE