Nuclear Theory·nucl-th

Friday·August 2, 2019

11 papers—7 primary·4 cross-listed

01
Ab Initio Structure of p-Shell Nuclei with Chiral Effective Field Theory and Daejeon16 Interactions
Pieter Maris🇺🇸 · Ik Jae Shin🇰🇷 · James P. Vary🇺🇸
We present No-Core Full Configuration results for the ground state energies of all particle-stable p-shell nuclei, as well as the excitation energies of more than 40 narrow states, excluding isobaric analog states. We used the chiral LENPIC nucleon-nucleon plus three-nucleon interaction at N2LO with semi-local coordinate space regulators, and also the phenomenological Daejeon16 nucleon-nucleon potential. With simple exponential extrapolations of the total energies of each state, binding energies and spectra are found to be in good agreement with experiment. Both interactions produce a trend towards some overbinding of nuclei at the upper end of the p-shell.
nucl-th8 citations
02
Centrality Dependence of Multiplicity Fluctuations in Ion-Ion Collisions from the Beam Energy Scan at FAIR
Anuj Chandra🇮🇳 · Bushra Ali🇮🇳 · Shakeel Ahmad🇮🇳
Multiplicity distributions and event-by-event multiplicity fluctuations in AuAu collisions at energies in future heavy-ion experiment at the Facility for Anti-proton and Ion Research (FAIR) are investigated. Events corresponding to FAIR energies are simulated in the frame work of Ultra Relativistic Quantum Molecular Dynamics (URQMD) model. It is observed that the mean and the width of multiplicity distributions monotonically increase with beam energy. The trend of variations of dispersion with mean number of participating nucleons for the centrality-bin width of 5\% are in accord with the Central Limit Theorem. The multiplicity distributions in various centrality bins as well as for full event samples are observed to obey Koba, Nielsen and Olesen (KNO) scaling. The trends of variations of scaled variance with beam energy are also found to support the KNO scaling predictions for larger collision centrality. The findings also reveal that the statistical fluctuations in 5\% centrality-bin width appear to be under control.
nucl-thhep-phAdv.High Energy Phys.(2019)·3 citations
03
How accurately we know the standard $^{252}$ Cf(sf) neutron multiplicity?
R. Capote · D. Neudecker
Small uncertainties obtained for the Neutron Standards have been associated with possible missing correlations in the input data, with an incomplete uncertainty budget of the employed experimental database or with unrecognized uncertainty sources common to many measurements. While further detailed studies may improve the first two issues, the issue of potential unrecognized uncertainties and correlations between different experiments has long been neglected. We address this gap with a test-case study ons the evaluation of the total neutron multiplicity of the $^{252}$ Cf(sf) source, which is included in the evaluation of the Thermal Neutron Constants within the Neutron Standards.
nucl-thnucl-exphysics.data-an1 citation
04
Perturbation Scheme for the Effective Nuclear Force
Kun Ratha Kean · Takashi Nishikawa · Yoritaka Iwata
Based on a systematic Hartree-Fock+BCS calculation, new perturbation scheme is proposed to modify the existing Skyrme-type effective nuclear force. Much attention is paid to have a better description of fission property of heavy nuclei. In terms of incorporating the nuclear medium effects on the fission barrier height more correctly, two typical Skyrme parameter sets (SkM* and SLy4) are modified. In conclusion, according to the comparison to experiments, the calculated fission barrier heights are improved by almost 90 $%$ .
nucl-thnucl-exJPS Conf.Proc.(2020)·2 citations
05
PHSD -- a microscopic transport approach for strongly interacting systems
E.L. Bratkovskaya🇩🇪 · W. Cassing🇩🇪 · P. Moreau🇩🇪 · L. Oliva🇩🇪 · O.E. Soloveva🇩🇪 · T. Song🇩🇪
We present the basic ideas of the Parton-Hadron-String Dynamics (PHSD) transport approach which is a microscopic covariant dynamical model for strongly interacting systems formulated on the basis of Kadanoff-Baym equations for Green's functions in phase-space representation (in 1st order gradient expansion beyond the quasi-particle approximation). The approach consistently describes the full evolution of a relativistic heavy-ion collision from the initial hard scatterings and string formation through the dynamical deconfinement phase transition to the strongly-interacting quark-gluon plasma (sQGP) as well as hadronization and the subsequent interactions in the expanding hadronic phase. The PHSD approach has been applied to p+p, p+A and A+A collisions from lower SIS to LHC energies and been successful in describing a large number of experimental data including single-particle spectra, collective flow and electromagnetic probes. Some highlights of recent PHSD results will be presented.
nucl-thhep-ph14 citations
06
IAEA Photonuclear Data Library 2019
T. Kawano · Y. S. Cho · P. Dimitriou · D. Filipescu · N. Iwamoto · V. Plujko · X. Tao · H. Utsunomiya · V. Varlamov · R. Xu · R. Capote · I. Gheorghe and 15 other authors
Photo-induced reaction cross section data are of importance for a variety of current or emerging applications, such as radiation shielding design and radiation transport analyses, calculations of absorbed dose in the human body during radiotherapy, physics and technology of fission reactors (influence of photo-reactions on neutron balance) and fusion reactors (plasma diagnostics and shielding), activation analyses, safeguards and inspection technologies, nuclear waste transmutation, medical isotope production and astrophysical applications. Since the release of the IAEA Photonuclear Data Library in 1999 however, new experimental data as well as new methods to assess the reliability of experimental cross sections have become available. Theoretical models and input parameters used to evaluate photo-induced reactions have improved significantly over the years. In addition, new measurements of partial photoneutron cross sections using mono-energetic photon beams and advanced neutron detection systems have been performed allowing for the validation of the evaluations and assessments of the experimental data. Furthermore, technological advances have led to the construction of new and more powerful gamma-beam facilities, therefore new data needs are emerging. We report our coordinated efforts to address these data needs and present the results of the new evaluations of more than 200 nuclides included in the new updated IAEA Photonuclear Data Library, where the photon energy goes up to 200 MeV. We discuss the new assessment method and make recommendations to the user community in cases where the experimental data are discrepant and the assessments disagree. In addition, in the absence of experimental data, we present model predictions for photo-induced reaction cross section on nuclides of potential interest to medical radioisotope production.
nucl-thNucl.Data Sheets(2020)·120 citations
07
Anomalous quartic term in the expansion of the symmetry energy
N. Zabari · S. Kubis · W. Wójcik
The quartic term in the framework of relativistic mean field theory with inclusion of scalar meson interactions is investigated. It is shown that the quartic term in the asymmetric expansion of nuclear matter energy may reach very large values. This makes the even power expansion of asymmetry questionable and suggests possible non-analytic contributions to the energy of matter.
nucl-thPRC(2019)·11 citations
08
Measurement of the nuclear symmetry energy parameters from gravitational wave events
Carolyn A. Raithel🇺🇸 · Feryal Ozel🇺🇸
The nuclear symmetry energy plays a role in determining both the nuclear properties of terrestrial matter as well as the astrophysical properties of neutron stars. The first measurement of the neutron star tidal deformability, from gravitational wave event GW170817, provides a new way of probing the symmetry energy. In this work, we report on new constraints on the symmetry energy from GW170817. We focus in particular on the low-order coefficients: namely, the value of the symmetry energy at the nuclear saturation density, S_0, and the slope of the symmetry energy, L_0. We find that the gravitational wave data are relatively insensitive to S_0, but that they depend strongly on L_0 and point to lower values of L_0 than have previously been reported, with a peak likelihood near L_0 ~ 20 MeV. Finally, we use the inferred posteriors on L_0 to derive new analytic constraints on higher-order nuclear terms.
↳ astro-ph.HEnucl-th39 citations
09
The virial expansion of attractively interacting Fermi gases in 1D, 2D, and 3D, up to fifth order
Y. Hou · J. E. Drut
The virial expansion characterizes the high-temperature approach to the quantum-classical crossover in any quantum many-body system. Here, we calculate the virial coefficients up to the fifth-order of Fermi gases in 1D, 2D, and 3D, with attractive contact interactions, as relevant for a variety of applications in atomic and nuclear physics. To that end, we discretize the imaginary-time direction and calculate the relevant canonical partition functions. In coarse discretizations, we obtain analytic results featuring relationships between the interaction-induced changes $Δ b_{3}$ , $Δ b_{4}$ , and $Δ b_{5}$ as functions of $Δ b_{2}$ , the latter being exactly known in many cases by virtue of the Beth-Uhlenbeck formula. Using automated-algebra methods, we push our calculations to progressively finer discretizations and extrapolate to the continuous-time limit. We find excellent agreement for $Δ b_{3}$ with previous calculations in all dimensions and we formulate predictions for $Δ b_{4}$ and $Δ b_{5}$ in 1D and 2D. We also provide, for a range of couplings,the subspace contributions $Δ b_{31}$ , $Δ b_{22}$ , $Δ b_{41}$ , and $Δ b_{32}$ , which determine the equation of state and static response of polarized systems at high temperature. As a performance check, we compare the density equation of state and Tan contact with quantum Monte Carlo calculations, diagrammatic approaches, and experimental data where available. Finally, we apply Padé and Padé-Borel resummation methods to extend the usefulness of the virial coefficients to approach and in some cases go beyond the unit-fugacity point.
↳ cond-mat.quant-gasnucl-thPRA(2020)·11 citations
10
A computational EXFOR database
Georg Schnabel
The EXFOR library is a useful resource for many people in the field of nuclear physics. In particular, the experimental data in the EXFOR library serves as a starting point for nuclear data evaluations. There is an ongoing discussion about how to make evaluations more transparent and reproducible. One important ingredient may be convenient programmatic access to the data in the EXFOR library from high-level languages. To this end, the complete EXFOR library can be converted to a MongoDB database. This database can be conveniently searched and accessed from a wide variety of programming languages, such as C++, Python, Java, Matlab, and R. This contribution provides some details about the successful conversion of the EXFOR library to a MongoDB database and shows simple usage examples to underline its merits. All codes required for the conversion have been made available online and are open-source. In addition, a Dockerfile has been created to facilitate the installation process.
↳ cs.DLnucl-exnucl-thphysics.comp-ph+1EPJ Web Conf.(2020)·2 citations
11
Canonical interpretation of the newly observed $Λ_{b} (6146)^{0}$ and $Λ_{b} (6152)^{0}$ via strong decay behaviors
Wei Liang🇨🇳 · Qi-Fang Lü🇨🇳 · Xian-Hui Zhong🇨🇳
Stimulated by the newly observed $Λ_{b} (6146)^{0}$ and $Λ_{b} (6152)^{0}$ resonances, we investigate the strong decays of the low-lying singly bottom baryons within the quark pair creation model. Considering their masses and decay modes, we tentatively assign these states as the $λ -$ mode $Λ_{b} (2 S)$ , $Λ_{b} (1 D)$ , $Σ_{b} (2 S)$ , and $Σ_{b} (1 P)$ states, and then estimate their strong decay widths. Compared with the experimental total widths and decay modes measured by the LHCb Collaboration, the $Λ_{b} (6146)^{0}$ and $Λ_{b} (6152)^{0}$ can be reasonably clarified into the $J^{P} = 5/ 2^{+}$ and $J^{P} = 3/ 2^{+}$ $Λ_{b} (1 D)$ sates respectively, while other canonical assignments are disfavored. Other low-lying bottom states are also presented, where various narrow states may have good potential to be observed in future LHCb experiments.
↳ hep-phhep-exnucl-thPRD(2019)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE