Nuclear Theory·nucl-th

Friday·January 12, 2024

15 papers—8 primary·7 cross-listed

01
[Submitted on 10 Jan 2024]
Predicting nucleon-nucleus scattering observables using nuclear structure theory
Aaina Thapa🇺🇸 · Jutta Escher🇺🇸 · Emanuel Chimanski🇺🇸 · Marc Dupuis🇫🇷 · Sophie Péru🇫🇷 · Walid Younes🇺🇸
Developing a predictive capability for inelastic scattering will find applications in multiple areas. Experimental data for neutron-nucleus inelastic scattering is limited and thus one needs a robust theoretical framework to complement it. Charged-particle inelastic scattering can be used as a surrogate for $(n, γ)$ reactions to predict capture cross sections for unstable nuclei. Our work uses microscopic nuclear structure calculations for spherical nuclei to obtain nucleon-nucleus scattering potentials and calculate cross sections for these processes. We implement the Jeukenne, Lejeune, Mahaux (JLM) semi-microscopic folding approach, where the medium effects on nuclear interaction are parameterized in nuclear matter to obtain the nucleon-nucleon $(N N)$ interaction in a medium at positive energies. We solve for the nuclear ground state using the Hartree-Fock-Bogliubov (HFB) many-body method, assuming the nucleons within the nucleus interact via the Gogny-D1M potential. The vibrational excited states of the target nucleus are calculated using the quasi-particle random phase approximation (QRPA). We demonstrate our approach for spherical nuclei in the medium-mass region, showing scattering results for the $^{90}$ Zr nucleus.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2401.05505 [pdf]
EPJ Web Conf.(2024)·7 citations
02
[Submitted on 11 Jan 2024]
Inference of Parameters for Back-shifted Fermi Gas Model using Feedback Neural Network
Peng-Xiang Du · Tian-Shuai Shang · Kun-Peng Geng · Jian Li · Dong-Liang Fang
The back-shifted Fermi gas model is widely employed for calculating nuclear level density (NLD) as it can effectively reproduce experimental data by adjusting parameters. However, selecting parameters for nuclei lacking experimental data poses a challenge. In this study, the feedforward neural network (FNN) was utilized to learn the level density parameters at neutron separation energy $a (S_{n})$ and the energy shift $Δ$ for 289 nuclei. Simultaneously, parameters for nearly 3000 nuclei are provided through the FNN. Using these parameters, calculations were performed for neutron resonance spacing in $s$ and $p$ waves, cumulative number of levels, and NLD. The FNN results were also compared with the calculated outcomes of the parameters from fitting experimental data (local parameters) and those obtained from systematic studies (global parameters), as well as the experimental data. The results indicate that parameters from the FNN achieve performance comparable to local parameters in reproducing experimental data. Moreover, for extrapolated nuclei, parameters from the FNN still offer a robust description of experimental data.
Comments:
11 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2401.05622 [pdf]
PRC(2024)·8 citations
03
[Submitted on 11 Jan 2024]
From NS observations to nuclear matter properties: a machine learning approach
Valéria Carvalho · Márcio Ferreira · Constança Providência
This study is devoted to the inference problem of extracting the nuclear matter properties directly from a set of mass-radius observations. We employ Bayesian neural networks (BNNs), which is a probabilistic model capable of estimating the uncertainties associated with its predictions. To simulate different noise levels on the $M (R)$ observations, we create three different sets of mock data. Our results show BNNs as an accurate and reliable tool for predicting the nuclear matter properties whenever the true values are not completely outside the training dataset statistics, i.e., if the model is not heavily dependent on its extrapolating capacities. Using real mass-radius pulsar data, the model predicted, for instance, $L_{sym} = 39.80 \pm 17.52$ MeV and $K_{sym} = - 101.67 \pm 62.86$ MeV ( $2 σ$ interval). Our study provides a valuable inference framework when new NS data becomes available.
Comments:
15 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2401.05770 [pdf]
PRD(2024)·21 citations
04
[Submitted on 11 Jan 2024]
Quadrupole dynamics of carbon isotopes and 10Be
H. Li · D. Fang · H. J. Ong · A. M. Shirokov · J. P. Vary · P. Yin · X. Zhao
Electric quadrupole (E2) moments and transitions provide measures of nuclear deformation and related collective structure. However, matrix elements of the E2 operator are sensitive to the nuclear wave function at large distances and are poorly convergent within the ab initio no-core shell model approach. We demonstrate for the first time that the ratio of neutron to proton quadrupole transition matrix elements, Mn/Mp, is well-converged in the ab initio no-core shell model and provides a new and robust tool for comparing with experimental results. We find that our parameter-free results for Mn/Mp for the carbon isotopes and 10Be compare well with experiment, where available, and offer new insight into the quadrupole dynamics of nuclear response.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2401.05776 [pdf]
PRC(2024)·8 citations
05
[Submitted on 11 Jan 2024]
Impact of the molecular resonances on the 12C+12C fusion reaction rate
Yasutaka Taniguchi · Masaaki Kimura
The properties of the low-energy 12C+12C molecular resonances, which potentially enhance the fusion reaction rate at low temperatures, have been investigated by a full-microscopic nuclear model employing various nuclear energy density functionals. We show that some density functionals plausibly describe the observed high-spin 12C+12C molecular resonances and predict many 0+ and 2+ resonances at low energies, which enhance the reaction rate. We also discuss how the uncertainty in the nuclear energy density functionals propagates to that of the reaction rate.
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2401.05803 [pdf]
PLB(2024)·17 citations
06
[Submitted on 11 Jan 2024]
Axially Symmetric Quadrupole-Octupole Model incorporating Sextic Potential
M. Chabab · A. El Batoul · L. El Ouaourti
We present an extended application of the analytic quadrupole octupole axially symmetric model, originally employed to study the octupole deformation and vibrations in light actinides using an infinite well potential (IW). In this work, we extend the model's applicability to a broader range of nuclei exhibiting octupole deformation by incorporating a sextic potential instead of the Davidson potential.Similarly to conventional models, such as AQOA-IW (for infinite square potential) and AQOA-D (for the Davidson potential), our proposed model is referred to as AQOA-S. By employing the sextic potential, phenomenologically represented as $v (β ~) = a_{1} β ~^{2} + a_{2} β ~^{4} + a_{3} β ~^{6}$ , we can derive analytical expressions for the energy spectra and transition rates (B(E1), B(E2), B(E3)). The energy spectra of the model are essentially governed by two critical parameters: $ϕ_{0}$ , indicating the balance between octupole and quadrupole strain, and $α$ , a key factor in adjusting the shape and behavior of the spectra through the sextic potential. In terms of applications, the study encompasses five isotopes, namely $^{222 - 226}$ Ra and $^{224, 226}$ Th. Significantly, our model demonstrates remarkable agreement with the corresponding experimental data, particularly for the recently determined B(EL) transition rates of $^{224}$ Ra, surpassing the performance of the model that employs the Davidson potential. The stability of the octupole deformation in $^{224}$ Ra adds particular significance to these findings.
Comments:
10 pages, 1 figure, accepted in Null. Phys. A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2401.05985 [pdf]
NPA(2024)·2 citations
07
[Submitted on 11 Jan 2024]
Implications of comprehensive nuclear and astrophysics data on the equations of state of neutron star matter
Sk Md Adil Imam · Tuhin Malik · Constança Providência · B. K. Agrawal
The equations of state (EoSs) governing neutron star (NS) matter obtained for both non-relativistic and relativistic mean-field models are systematically confronted with a diverse set of terrestrial data and astrophysical observations within the Bayesian framework. The terrestrial data, spans from bulk properties of finite nuclei to the heavy-ion collisions, constrain the symmetric nuclear matter EoS and the symmetry energy up to twice the saturation density ( $ρ_{0}$ = 0.16 fm $^{- 3}$ ). The astrophysical observations encompass the NS radius, the tidal deformability, and the lower bound on maximum mass. Three distinct posterior distributions of EoSs are generated by gradually updating the priors with different constraints: (i) only the maximum NS mass, (ii) incorporating additional terrestrial data, (iii) combining both the terrestrial data and astrophysical observations. These EoS distributions are then compared using the Kullback-Liebler divergence which highlights the significant constraints imposed on the EoSs by the currently available lower bound of NS maximum mass and terrestrial data. The remaining astrophysical observations marginally refine the EoS within the density range $\sim$ 2-3 $ρ_{0}$ . It is observed that the relativistic mean field model yields stiffer EoS around the saturation density, but predict smaller values of the speed of sound and proton fraction in the interior of massive stars.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2401.06018 [pdf]
PRD(2024)·27 citations
08
[Submitted on 11 Jan 2024]
Landscape of nuclear deformation softness with spherical quasi-particle random phase approximation
Le-Anh Nguyen · Minh-Loc Bui · Panagiota Papakonstantinou · Naftali Auerbach
We investigate the stability and softness of nuclei against quadrupole, octupole, and hexadecapole deformation. By applying the spherical Skyrme-force Hartree-Fock Bardeen-Cooper-Schrieffer quasi-particle random phase approximation, we diagnose ground-state deformation when imaginary solutions are obtained, i.e., the spherical ground state {\em collapses}. We also calculate the multipole polarizability in spherical nuclei with no collapse, as a measure of softness. This numerically light and theoretically sound method is found able to capture deformation patterns across the nuclide chart. The connection between the intrinsic shape of nuclei and the dynamics of their low-lying collective states is established and the role of shell structure is discussed.
Comments:
8 pages, 8 figures, accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2401.06117 [pdf]
PRC(2024)·6 citations
09
[Submitted on 9 Jan 2024] (cross-list from physics.plasm-ph)
Effect of Longitudinal Fluctuations of $3$ D Weizsäcker-Williams Field on Pressure Isotropization of Glasma
Hidefumi Matsuda🇨🇳 · Xu-Guang Huang🇨🇳
We investigate the effects of boost invariance breaking on the isotropization of pressure in the glasma, using the $3 + 1$ D glasma simulation. The breaking is attributed to spatial fluctuations of the classical color charge density along the collision axis. We present numerical results for pressure and energy density at mid-rapidity and across a wider rapidity region. It is found that, despite varying longitudinal correlation lengths, the behaviors of the pressure isotropizations are qualitatively similar. The numerical results suggest that, in the initial stage, longitudinal color electromagnetic fields develop, similar to those in the boost invariant glasma. Subsequently, these fields evolve into a dilute glasma, expanding longitudinally in a manner akin to a dilute gas. We also show that the energy density at mid-rapidity exhibits a $1/ τ$ decay in the dilute glasma stage.
Comments:
16 page, 6 figures
Subjects:
Plasma Physics (physics.plasm-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2401.04296 [pdf]
Entropy(2024)·9 citations
10
[Submitted on 10 Jan 2024] (cross-list from hep-lat)
Trace anomaly form factors from lattice QCD
Bigeng Wang🇺🇸 · Fangcheng He🇺🇸 · Gen Wang🇫🇷 · Terrence Draper🇺🇸 · Jian Liang🇨🇳 · Keh-Fei Liu🇺🇸 · Yi-Bo Yang🇨🇳
The hadron mass can be obtained through the calculation of the trace of the energy-momentum tensor in the hadron which includes the trace anomaly and sigma terms. The anomaly due to conformal symmetry breaking is believed to be an important ingredient for hadron mass generation and confinement. In this work, we will present the calculation of the glue part of the trace anomaly form factors of the pion up to $Q^{2} \sim 4.3 GeV^{2}$ and the nucleon up to $Q^{2} \sim 1 GeV^{2}$ . The calculations are performed on a domain wall fermion ensemble with overlap valence quarks at seven valence pion masses varying from $\sim 250$ to $\sim 540$ MeV, including the unitary point $\sim 340$ MeV. We calculate the radius of the glue trace anomaly for the pion and the nucleon from the $z$ expansion. By performing a two-dimensional Fourier transform on the glue trace anomaly form factors in the infinite momentum frame with no energy transfer, we also obtain their spatial distributions for several valence quark masses. The results are qualitatively extrapolated to the physical valence pion mass with systematic errors from the unphysical sea quark mass, discretization effects in the renormalization sum rule, and finite-volume effects to be addressed in the future. We find the pion's form factor changes sign, as does its spatial distribution, for light quark masses. This explains how the trace anomaly contribution to the pion mass approaches zero toward the chiral limit.
Comments:
This is the version accepted for publication in Physical Review D
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2401.05496 [pdf]
PRD(2024)·35 citations
11
[Submitted on 10 Jan 2024] (cross-list from hep-ph)
Orbital Angular Momentum Small- $x$ Evolution: Exact Results in the Large- $N_{c}$ Limit
Brandon Manley🇺🇸
We construct an exact solution to the revised small- $x$ orbital angular momentum (OAM) evolution equations derived recently, based on an earlier work. These equations are derived in the double logarithmic approximation (summing powers of $α_{s} ln^{2} (1/ x)$ with $α_{s}$ the strong coupling constant and $x$ the Bjorken $x$ variable) and the large- $N_{c}$ limit, with $N_{c}$ the number of quark colors. From our solution, we extract the small- $x$ , large- $N_{c}$ expressions of the quark and gluon OAM distributions. Additionally, we determine the large- $N_{c}$ small- $x$ asymptotics of the OAM distributions to be \begin{align} \notag L_{q+\bar{q}}(x,Q^2) \sim L_G(x,Q^2) \sim \Delta \Sigma (x,Q^2) \sim \Delta G(x,Q^2) \sim \left(\frac{1}{x} \right)^{\alpha_h}, \end{align} with the intercept $α_{h}$ the same as obtained in the small- $x$ helicity evolution, which can be approximated as $α_{h} \approx 3.66074 \frac{α _{s} N _{c}}{2 π}$ . This result is in complete agreement with the literature. Additionally, we calculate the ratio of the quark and gluon OAM distributions to the flavor-singlet quark and gluon helicity parton distribution functions respectively in the small- $x$ region.
Comments:
27 pages, 2 figures; v2: typos corrected, references added, appendix C modified, 22 pages, 2 figures. Signs corrected, discussion expanded; v4: typos corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2401.05508 [pdf]
JHEP(2024)·15 citations
12
[Submitted on 11 Jan 2024] (cross-list from astro-ph.HE)
Astromers: Status and Prospects
G. Wendell Misch · Matthew R. Mumpower
The extreme temperatures and densities of many astrophysical environments tends to destabilize nuclear isomers by inducing transitions to higher energy states. Those states may then cascade to ground. However, not all environments destabilize all isomers. Nuclear isomers which retain their metastable character in pertinent astrophysical environments are known as astrophysically metastable nuclear isomers, or "astromers". Astromers can influence nucleosynthesis, altering abundances or even creating new pathways that would otherwise be inaccessible. Astromers may also release energy faster or slower relative to their associated ground state, acting as heating accelerants or batteries, respectively. In stable isotopes, they may even simply remain populated after a cataclysmic event and emit observable x- or $γ$ -rays. The variety of behaviors of these nuclear species and the effects they can have merit careful consideration in nearly every possible astrophysical environment. Here we provide a brief overview of astromers past and present, and we outline future work that will help to illuminate their role in the cosmos.
Comments:
39 pages(10 of the 16 of them references), 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2401.05598 [pdf]
Eur.Phys.J.ST(2024)·13 citations
13
[Submitted on 11 Jan 2024] (cross-list from hep-lat)
Advancing real-time Yang-Mills: towards real-time observables from first principles
Kirill Boguslavski · Paul Hotzy · David I. Müller🇦🇹
The complex Langevin (CL) method shows great promise in enabling the calculation of observables for theories with complex actions. Nevertheless, real-time quantum field theories have remained largely unsolved due to the particular severity of the sign problem. In this contribution, we discuss our recent progress in applying CL to a thermal SU(2) Yang-Mills theory on a 3+1 dimensional lattice. We present our anisotropic kernel that stabilizes the CL approach for real times longer than the inverse temperature - a first for Yang-Mills theory. We provide explicit evidence of reproducing symmetries and relations among different types of propagators when the complex time path approaches the Schwinger-Keldysh contour. This method paves the way for calculating transport coefficients and other real-time observables from first principles.
Comments:
10 pages, 7 figures; Proceedings of the 40th International Symposium on Lattice Field Theory (LATTICE2023)
Subjects:
High Energy Physics — Lattice (hep-lat); cond-mat.other (cond-mat.other); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2401.05723 [pdf]
PoS(2024)·2 citations
14
[Submitted on 11 Jan 2024] (cross-list from physics.atom-ph)
Full leading-order nuclear polarization in highly charged ions
Igor A. Valuev · Natalia S. Oreshkina (Max-Planck-Institut für Kernphysik, Heidelberg, Germany)
The nuclear-polarization corrections to the energy levels of highly charged ions are systematically investigated to leading order in the fine-structure constant. To this end, the notion of effective photon propagators with nuclear-polarization insertions is employed, where the nuclear excitation spectrum is calculated by means of the Hartree-Fock-based random-phase approximation. The effective Skyrme force is used to describe the interaction between nucleons, and the model dependence is analyzed. To leading order, the formalism predicts two contributions given by the effective vacuum-polarization and self-energy diagrams. The existing ambiguity around the vacuum-polarization term is resolved by demonstrating that it is effectively absorbed in the standard finite-nuclear-size correction. The self-energy part is evaluated with the full electromagnetic electron-nucleus interaction taken into account, where the importance of the effects of the nuclear three-currents is emphasized.
Comments:
12 pages, 3 figures, 4 tables; typos corrected, Table I and Fig. 3 slightly updated
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2401.05904 [pdf]
PRA(2024)·11 citations
15
[Submitted on 11 Jan 2024] (cross-list from physics.atom-ph)
The spin-flip-induced quadrupole resonance in odd- $A$ exotic atoms
Fredrik P. Gustafsson🇨🇭 · Daniel Pęcak🇵🇱 · Tomasz Sowiński🇵🇱
We examine the possible existence of quadrupole resonances in exotic atoms containing odd- $A$ nuclei. We find that the spin-flip of the de-exciting exotic particle can induce a resonance, altering the orbital angular momentum of the nucleus by one quanta. This process results in an excited nucleus with a suppression in x-ray photon emissions during the exotic atom cascade. We provide specific cases of antiprotonic atoms of stable elements where this resonance effect is expected to occur. The study of this phenomena may provide insight into the strong interaction of deeply bound antiprotonic states in the proximity of the unpaired nucleon, and serve as a tool for probing short-lived excited nuclear states.
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
2401.06063 [pdf]
PRC(2024)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE