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arXiv 2022年

作者： Giuliani, Pablo Godbey, Kyle Bonilla, Edgard Viens, Frederi Piekarewicz, Jorge FRIB/NSCL Laboratory Michigan State University East LansingMI48824 United States Department of Statistics and Probability Michigan State University East LansingMI48824 United States Department of Physics Stanford University StanfordCA94305 United States Rice University Department of Statistics HoustonTX77005 United States Department of Physics Florida State University TallahasseeFL32306 United States

A covariant energy density functional is calibrated using a principled Bayesian statistical framework informed by experimental binding energies and charge radii of several magic and semi-magic nuclei. The Bayesian sampling required for the calibration is enabled by the emulation of the high-fidelity model through the implementation of a reduced basis method (RBM)—a set of dimensionality reduction techniques that can speed up demanding calculations involving partial differential equations by several orders of magnitude. The RBM emulator we build—using only 100 evaluations of the high-fidelity model—is able to accurately reproduce the model calculations in tens of milliseconds on a personal computer, an increase in speed of nearly a factor of 3,300 when compared to the original solver. Besides the analysis of the posterior distribution of parameters, we present predictions with properly estimated uncertainties for observables not included in the fit, specifically the neutron skin thickness of 208Pb [1–3] and 48Ca [4], as reported by PREX and CREX collaborations. The straightforward implementation and outstanding performance of the RBM makes it an ideal tool for assisting the nuclear theory community in providing reliable estimates with properly quantified uncertainties of physical observables. Such uncertainty quantification tools will become essential given the expected abundance of data from the recently inaugurated and future experimental and observational facilities. © 2022, CC BY.

关键词： Binding energy

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Quadrupole collectivity and shell closure in neutron-rich nuclei near N=126

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Physical Review C 2019年第5期99卷 054329-054329页

作者： X. Y. Wu J. M. Yao FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA

We present a comprehensive study on the low-lying states of neutron-rich Er, Yb, Hf, and W isotopes across the N=126 shell with a multireference covariant density functional theory. Beyond-mean-field effects from shape mixing and symmetry restoration on the observables that are relevant for understanding quadrupole collectivity and underlying shell structure are investigated. The general features of low-lying states in closed-shell nuclei are retained in these four isotopes around N=126, even though the shell gap is overall quenched by about 30% with the beyond-mean-field effects. These effects are consistent with the previous generator-coordinate calculations based on Gogny forces, but much smaller than that predicted by the collective Hamiltonian calculation. It implies that the beyond-mean-field effects on the r-process abundances before the third peak at A≈195 might be more moderate than that reported by Arcones and Bertsch [Phys. Rev. Lett. 108, 151101 (2012)].

关键词： Binding energy & masses Collective levels Nuclear density functional theory 190 ≤ A ≤ 219

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Merging ab initio theory and few-body approach for (d,p) reactions

arXiv

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arXiv 2019年

作者： Rotureau, Jimmy Potel, G. Li, W. Nunes, F.M. NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States

A framework for A(d, p)B reactions is introduced by merging the microscopic approach to computing the properties of the nucleon-target systems and the three-body n+p+A reaction formalism, thus providing a consistent link between the reaction cross sections and the underlying microscopic structure. In this first step toward a full microscopic description, we focus on the inclusion of the neutron-target microscopic properties. The properties of the neutron-target subsystem are encapsulated in the Green’s function which is computed with the Coupled Cluster theory using a chiral nucleon-nucleon and three-nucleon interactions. Subsequently, this many-body information is introduced in the few-body Green’s Function Transfer approach to (d, p) reactions. Our benchmarks on stable targets 40,48Ca show an excellent agreement with the data. We then proceed to make specific predictions for (d, p) on neutron rich 52,54Ca isotopes. These predictions are directly relevant to testing the new magic numbers N = 32, 34 and are expected to be feasible in the first campaign of the projected frib facility. Copyright © 2019, The Authors. All rights reserved.

关键词： Merging

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Near-threshold dipole strength in 10Be with isoscalar character

arXiv

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arXiv 2025年

作者： Chen, J. Ayyad, Y. Bazin, D. Mittig, W. Serikow, M.Z. Keeley, N. Wang, S.M. Zhou, B. Zamora, J.C. Beceiro-Novo, S. Cortesi, M. DeNudt, M. Heinitz, S. Giraud, S. Gueye, P. Hoffman, C.R. Kay, B.P. Maugeri, E.A. Monteagudo, B.G. Li, H. Liu, W.P. Muñoz, A. Ndayisabye, F. Pereira, J. Rijal, N. Santamaria, C. Schumann, D. Watwood, N. Votta, G. Yin, P. Yuan, C.X. Zhang, Y.N. College of Science Southern University of Science and Technology Guangdong Shenzhen518055 China Physics Division Argonne National Laboratory LemontIL60439 United States IGFAE Universidade de Santiago de Compostela Santiago de CompostelaE-15782 Spain FRIB/NSCL Laboratory Michigan State University East LansingMI48824 United States National Centre for Nuclear Research ul. Andrzeja Soltana 7 Otwock05-400 Poland Institute of Modern Physics Fudan University Shanghai200433 China Shanghai Research Center for Theoretical Nuclear Physics NSFC Fudan University Shanghai200438 China Universidade da Coruña Departamento de Física y Ciencias de la Tierra CITENI Campus Industrial Ferrol15471 Spain Laboratory of Radiochemistry Paul Scherrer Institute Villigen Switzerland Department of Physics Hope College HollandMI49422-9000 United States Institute of Modern Physics Chinese Academy of Sciences Lanzhou730000 China China Institute of Atomic Energy P. O. Box 27547 Beijing102413 China College of Physics and Engineering Henan University of Science and Technology Luoyang471023 China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen University Zhuhai519082 China

Isoscalar dipole transitions are a distinctive fingerprint of cluster structures. A 1− resonance at 7.27(10) MeV, located just below the α-emission threshold, has been observed in the deuteron inelastic scattering reactions off 10Be. The deformation lengths of the excited states in 10Be below 9 MeV have been inferred from the differential cross sections using coupled channel calculations. This observed 1− resonance has isoscalar characteristics and exhausts approximately 5%-15% of the isoscalar dipole energy-weighted sum rule, providing evidence for pronounced α cluster structure in 10Be. The Gamow coupled channel approach supports this interpretation and suggests the near-threshold effect might be playing an important role in this excitation energy domain. The α+α+n+n four-body calculation reproduces the observed enhanced dipole strength, implying that the four-body cluster structure is essential to describe the 1− states in 10Be. © 2025, CC BY.

关键词： Inelastic scattering

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Neutron Drip Line in the Ca Region from Bayesian Model Averaging

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Physical Review Letters 2019年第6期122卷 062502-062502页

作者： Léo Neufcourt Yuchen Cao (曹宇晨) Witold Nazarewicz Erik Olsen Frederi Viens Department of Statistics and Probability Michigan State University East Lansing Michigan 48824 USA FRIB Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Physics and Astronomy and NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Physics and Astronomy and FRIB Laboratory Michigan State University East Lansing Michigan 48824 USA

The region of heavy calcium isotopes forms the frontier of experimental and theoretical nuclear structure research where the basic concepts of nuclear physics are put to stringent test. The recent discovery of the extremely neutron-rich nuclei around Ca60 O. B. Tarasov et al. [Phys. Rev. Lett. 121, 022501 (2018)] and the experimental determination of masses for Ca55–57 S. Michimasa et al. [Phys. Rev. Lett. 121, 022506 (2018)] provide unique information about the binding energy surface in this region. To assess the impact of these experimental discoveries on the nuclear landscape’s extent, we use global mass models and statistical machine learning to make predictions, with quantified levels of certainty, for bound nuclides between Si and Ti. Using a Bayesian model averaging analysis based on Gaussian-process-based extrapolations we introduce the posterior probability pex for each nucleus to be bound to neutron emission. We find that extrapolations for drip-line locations, at which the nuclear binding ends, are consistent across the global mass models used, in spite of significant variations between their raw predictions. In particular, considering the current experimental information and current global mass models, we predict that Ca68 has an average posterior probability pex≈76% to be bound to two-neutron emission while the nucleus Ca61 is likely to decay by emitting a neutron (pex≈46%).

关键词： Nuclear binding Nuclear forces Nuclear structure & decays Monte Carlo methods Nuclear density functional theory

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Quadrupole collectivity and shell closure in neutron-rich nuclei around N = 126

arXiv

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arXiv 2019年

作者： Wu, X.Y. Yao, J.M. College of Physics and Communication Electronics Jiangxi Normal University Nanchang330022 China FRIB/NSCL Laboratory Michigan State University East LansingMI48824 United States

We present a comprehensive study on the low-lying states of neutron-rich Er, Yb, Hf, and W isotopes across the N = 126 shell with a multi-reference covariant density functional theory. Beyond mean-field effects from shape mixing and symmetry restoration on the observables that are relevant for understanding quadrupole collectivity and underlying shell structure are investigated. The general features of low-lying states in closed-shell nuclei are retained in these four isotopes around N = 126, even though the shell gap is overall quenched by about 30% with the beyond mean-field effects. These effects are consistent with the previous generator-coordinate calculations based on Gogny forces, but much smaller than that predicted by the collective Hamiltonian calculation. It implies that the beyond mean-field effects on the r-process abundances before the third peak at A ∼ 195 might be more moderate than that found in A. Arcones and G. F. Bertsch, Phys. Rev. Lett. 108, 151101 (2012). Copyright © 2019, The Authors. All rights reserved.

关键词： Shells (structures)

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ADG: Automated generation and evaluation of many-body diagrams III. Bogoliubov in-medium similarity renormalization group formalism

arXiv

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arXiv 2021年

作者： Tichai, Alexander Arthuis, P. Hergert, H. Duguet, T. Technische Universität Darmstadt Department of Physics Darmstadt64289 Germany ExtreMe Matter Institute EMMI GSI Helmholtzzentrum für Schwerionenforschung GmbH Darmstadt64291 Germany Max-Planck-Institut für Kernphysik Saupfercheckweg 1 Heidelberg69117 Germany NSCL/FRIB Laboratory Department of Physics and Astronomy Michigan State University East LansingMI48824-1321 United States IRFU CEA Université Paris-Saclay Gif-sur-Yvette91191 France KU Leuven Instituut voor Kern- en Stralingsfysica Leuven3001 Belgium

The goal of the present paper is twofold. First, a novel expansion many-body method applicable to superfluid open-shell nuclei, the so-called Bogoliubov in-medium similarity renormalization group (BIMSRG) theory, is formulated. This generalization of standard single-reference IMSRG theory for closed-shell systems parallels the recent extensions of coupled cluster, self-consistent Green’s function or many-body perturbation theory. Within the realm of IMSRG theories, BIMSRG provides an interesting alternative to the already existing multi-reference IMSRG (MR-IMSRG) method applicable to open-shell nuclei. The algebraic equations for low-order approximations, i.e., BIMSRG(1) and BIMSRG(2), can be derived manually without much difficulty. However, such a methodology becomes already impractical and error prone for the derivation of the BIMSRG(3) equations, which are eventually needed to reach high accuracy. Based on a diagrammatic formulation of BIMSRG theory, the second objective of the present paper is thus to describe the third version (v3.0.0) of the ADG code that automatically (1) generates all valid BIMSRG(n) diagrams and (2) evaluates their algebraic expressions in a matter of seconds. This is achieved in such a way that equations can easily be retrieved for both the flow equation and the Magnus expansion formulations of BIMSRG. Expanding on this work, the first future objective is to numerically implement BIMSRG(2) (eventually BIMSRG(3)) equations and perform ab initio calculations of mid-mass open-shell nuclei. Copyright © 2021, The Authors. All rights reserved.

关键词： Statistical mechanics

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Analysis of beam position monitor requirements with bayesian gaussian regression

arXiv

引用

arXiv 2019年

作者： Li, Yongjun Hao, Yue Cheng, Weixing Rainer, Robert Brookhaven National Laboratory UptonNY11973 United States FRIB/NSCL Michigan State University East LansingMI48864 United States Argonne National Laboratory ArgonneIL60439 United States

With a Bayesian Gaussian regression approach, a systematic method for analyzing a storage ring's beam position monitor (BPM) system requirements has been developed. The ultimate performance of a ring-based accelerator, based on brightness or luminosity, is determined not only by global parameters, but also by local beam properties at some particular points of interest (POI). BPMs used for monitoring the beam properties, however, cannot be located at these points. Therefore, the underlying and fundamental purpose of a BPM system is to predict whether the beam properties at POIs reach their desired values. The prediction process can be viewed as a regression problem with BPM readings as the training data, but containing random noise. A Bayesian Gaussian regression approach can determine the probability distribution of the predictive errors, which can be used to conversely analyze the BPM system requirements. This approach is demonstrated by using turnbyturn data to reconstruct a linear optics model, and predict the brightness degradation for a ring-based light source. The quality of BPMs was found to be more important than their quantity in mitigating predictive errors. Copyright © 2019, The Authors. All rights reserved.

关键词： Requirements engineering

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Structure and decay of the extremely proton-rich nuclei O11,12

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Physical Review C 2019年第5期99卷 054302-054302页

作者： S. M. Wang (王思敏) W. Nazarewicz R. J. Charity L. G. Sobotka FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Physics and Astronomy and FRIB Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Chemistry Washington University St. Louis Missouri 63130 USA Department of Physics Washington University St. Louis Missouri 63130 USA

Background: The recent observation of the unbound nucleus O11 offers the unique possibility to study how the structure and dynamics of two-proton (2p) decay is affected by the removal of one neutron from O12, and provides important information on the Thomas-Ehrman effect in the mirror pairs O3811−Li8311 and O4812−Be8412, which involve the 2p emitters O11 and O12.

关键词： Cluster models Lifetimes & widths Nuclear structure & decays Proton emission

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Energy spectrum of neutron-rich helium isotopes: Complex made simple

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Physical Review C 2018年第6期98卷 061302(R)-061302(R)页

作者： K. Fossez J. Rotureau W. Nazarewicz NSCL/FRIB Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Physics and Astronomy NSCL/FRIB Laboratory Michigan State University East Lansing Michigan 48824 USA

We demonstrate that the intricate energy spectrum of neutron-rich helium isotopes can be straightforwardly described by taking advantage of the low-energy properties of neutron-neutron interaction and the scale separation that is present in diluted drip-line systems. By using arguments based on the halo effective field theory, we carry out a parameter reduction of the complex-energy configuration interaction framework in the spd space, including resonant and scattering states. By constraining the core potential to α−n scattering phase shifts and adjusting the strength of the spin-singlet central neutron-neutron interaction, we reproduce experimental energies and widths of 5–8He within tens of keV precision. We predict a parity inversion of narrow resonances in He9 and show that the ground state of He10 is an s-wave-dominated configuration that could decay through two-neutron emission. This threshold state can be viewed as a “double-halo” structure in an analogy to the atomic He34He2 trimer.

关键词： Energy levels & level densities Few-body systems Nuclear forces Nuclear structure & decays Rare & new isotopes 6 ≤ A ≤ 19

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