Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session DK: Nuclear Theory II |
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Chair: Kristina Launey, Louisiana State University Room: Hilton Queen's 4 |
Thursday, October 25, 2018 9:00AM - 9:15AM |
DK.00001: Pionless effective field theory for atomic nuclei and lattice nuclei Aaina Bansal, Sven Binder, Andreas Ekström, Gaute Hagen, Gustav R Jansen, Thomas Papenbrock We compute the medium-mass nuclei $^{16}$O and $^{40}$Ca using |
Thursday, October 25, 2018 9:15AM - 9:30AM |
DK.00002: Recent developments in applying Bayesian statistics to effective field theories Richard J Furnstahl, Jordan A Melendez, Daniel Robertson Phillips, Sarah Wesolowski Uncertainty quantification (UQ) is an essential part and one of the main advantages of applying effective field theories (EFT) to low-energy nuclear physics. A Bayesian statistical framework is particularly well suited for this task, as EFT expectations regarding naturalness and truncation errors can be encoded through prior probability distribution functions (PDFs). The specification of priors means that all theoretical assumptions are explicit in the calculation of the posterior PDFs, making such an analysis reproducible. The BUQEYE collaboration (``Bayesian Uncertainty Quantification: Errors for Your EFT'') has the overall goal of full UQ and associated diagnostics for EFT predictions using Bayesian statistics. This includes parameter estimation, uncertainty propagation to observables, model checking (``Is the EFT and our model for errors working?''), model selection (``Is one EFT implementation better than another?''), and the use of Bayesian statistical methods as a physics diagnostic tool. We will give background and selected results from recent and ongoing work by the BUQEYEs. |
Thursday, October 25, 2018 9:30AM - 9:45AM |
DK.00003: Bayesian Discrepancy Models for Full Uncertainty Propagation in Effective Field Theories Jordan Andrew Melendez A full accounting of the uncertainties inherent in chiral effective field theory (χEFT) is a requirement for rigorous uncertainty quantification across the nuclear chart. We propose a Bayesian discrepancy model that is informed by the convergence of χEFT to quantify the size of its higher-order contributions. Based in Gaussian processes, the discrepancy due to χEFT truncation can then be used for two important goals: (1) to obtain better estimates of the χEFT parameters when fit to data and (2) to quantify uncertainties in predictions from χEFTs that have already been fit. We show how the discrepancy model arises naturally from the physics of χEFT, how the discrepancy term appears in fitting and prediction equations, and discuss the application of these techniques to the search for neutrinoless double beta decay. |
Thursday, October 25, 2018 9:45AM - 10:00AM |
DK.00004: Rearrangement potential in scattering state with interactions of chiral effective field theory Michio Kohno Although the importance of rearrangement effects in the description of ground state properties of nuclei has been recognized, the incorporation of them in a microscopic description of an optical-model potential has been limited. Extending the study of the microscopic optical-model potential [1] using interactions of chiral effective field theory, a second-order rearrangement potential in scattering state is calculated in nuclear matter. Pauli blocking effects in ladder correlations in a target nucleus by an incoming nucleon appear as a real and repulsive rearrangement potential. To estimate the rearrangement effect in a finite nucleus, a simple local density approximation is adopted. The second-order repulsive contribution is found about 5 MeV at normal density and smaller at low densities. While the depth of the optical-model potential becomes closer to the empirical one, the good account of nucleon-nucleus elastic scattering persists. The repulsive contribution can help improving the description of nucleus-nucleus scattering at larger angles. [1] M. Toyokawa et al., Prog. Theor. Exp. Phys. 2018, 023D03 (2018). |
Thursday, October 25, 2018 10:00AM - 10:15AM |
DK.00005: Convergence in the ab initio symplectic no-core configuration interaction framework Anna McCoy, Mark Caprio, Tomáš Dytrych A major challenge in quantitatively predicting nuclear structure directly from realistic nucleon-nucleon interactions arises due to an explosion in the dimension of the traditional configuration interaction basis as the number of nucleons and included shells increases. Combining symplectic symmetry with the no-core configuration interaction framework provides a means of identifying and restricting the basis to include only the highly excited configurations which dominantly contribute to the nuclear wavefunction, thereby reducing the size of the basis necessary to obtain accurate results. We present a framework for ab initio symplectic no-core configuration interaction (SpNCCI) calculations of the nuclear problem and explore convergence behavior of calculations of p-shell nuclei in this framework. |
Thursday, October 25, 2018 10:15AM - 10:30AM |
DK.00006: A solution to the puzzle of quenched beta-decays Gaute Hagen A central puzzle has been that observed β-decay rates are systematically smaller than theoretical predictions. This was attributed to an apparent quenching of the fundamental coupling constant gA in the nucleus by a factor of about 0.75. The origin of this quenching is controversial and has so far eluded a first-principles theoretical understanding. This talk presents a solution to this puzzle, and shows that this quenching can be explained from two-body currents and many-body correlations. Using interactions and currents from chiral effective field theory that describe Gamow-Teller strength in light nuclei well, I will present a first principles computation of the Gamow-Teller strength in 100Sn. By developing high order coupled-cluster methods we obtain a quenching factor in the range 0.73-0.85 from two-body currents which depends somewhat on the employed Hamiltonian. Our results are consistent with experimental data, including the pioneering measurement for 100Sn [1,2]. These theoretical advances have been enabled by systematic effective field theories combined with powerful quantum many-body techniques and ever increasing computational power. [1] Hinke, C. B. et al., Nature 486, 341-345 (2012). [2] Batist, L. et al. Eur. Phys. J. A 46, 45-53 (2010).
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Thursday, October 25, 2018 10:30AM - 10:45AM |
DK.00007: Abstract Withdrawn
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Thursday, October 25, 2018 10:45AM - 11:00AM |
DK.00008: A Study of β-decay and Delayed Neutron of Odd Nuclei Including Core Polarization Effect Futoshi Minato There are various theoretical works based on mean-field theory + quasiparticle random phase approximation (QRPA) calculating β-decay half-lives of nuclei. For the moment, they are the only approaches that are based on a microscopic theory applicable for the systematic calculation in the nuclear chart. A special attention is needed when calculating odd nuclei because of the presence of core polarization effect (CPE). However, the systematic calculation of aforementioned microscopic theories has approximated the calculation of odd nuclei in a simple way. This may cause a problem when predicting unmeasured half-lives, delayed neutron (DN) emission probabilities, etc. Under this background, the CPE on β-decay and DN are investigated. We assume that odd nucleus consists of active even-even nucleus and valence particle(s), and use a perturbation theory to estimate the CPE. Core phonon states to be excited are calculated by HFB + QRPA. We found the CPE mitigates an odd-even straggling of half-lives found in no CPE calculations, which is consistent with experiments. |
Thursday, October 25, 2018 11:00AM - 11:15AM |
DK.00009: ABSTRACT WITHDRAWN
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Thursday, October 25, 2018 11:15AM - 11:30AM |
DK.00010: Uncertainty quantification in nuclear shell-model calculations Sota Yoshida, Noritaka Shimizu, Tomoaki Togashi, Takaharu Otsuka In addition to successful descriptions with phenomenological effective interactions so far, shell-model calculations play now key roles to investigate various nuclear observables based on state-of-the-art realistic nuclear potentials from chiral effective field theory and ab initio methods to derive effective interactions for a valence space. Within this context, it is urgent task to investigate the validity of valence shell model itself, which states should be described within a given model space. Quantifying the uncertainties in shell-model effective interactions for a given model space provide us important informations, (possible) missing contributions in current nuclear potential and/or many-body methods to derive eff. int., comparisons with experimental data in a higher level, and so on. |
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