Bulletin of the American Physical Society
Fall 2022 Meeting of the APS Division of Nuclear Physics
Volume 67, Number 17
Thursday–Sunday, October 27–30, 2022; Time Zone: Central Daylight Time, USA; New Orleans, Louisiana
Session EK: Nuclear Theory II |
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Chair: Amy Nicholson, University of North Carolina Room: Hyatt Regency Hotel Imperial 5AB |
Friday, October 28, 2022 10:30AM - 10:42AM |
EK.00001: Auxiliary Field Diffusion Monte Carlo calculations of magnetic moments of light nuclei from χEFT Joshua D Martin, Samuel J Novario, Stefano Gandolfi, Joseph A Carlson, Ingo Tews We calculate the magnetic moments of light nuclei (A < 20) using the auxiliary field diffusion quantum Monte Carlo method with two- and three-nucleon forces from chiral effective field theory (χEFT) and consistent electromagnetic currents also obtained from χEFT. In addition to theoretical estimates for magnetic moments for a collection of light nuclei, we also present order-by-order estimates of the theoretical uncertainty stemming from the truncation of the chiral expansion for select nuclei. |
Friday, October 28, 2022 10:42AM - 10:54AM |
EK.00002: The quasi-deuteron model at low renormalization group resolution Anthony J Tropiano, Richard J Furnstahl, Scott K Bogner, Mostofa A Hisham The quasi-deuteron model introduced by Levinger is used to explain cross sections for knocking out high-momentum protons in photo-absorption on nuclei. Assuming a one-body reaction operator, the nuclear wave function must include two-body short-range correlations (SRCs) with deuteron-like quantum numbers. Here we describe the quasi-deuteron model at low renormalization group (RG) resolution and determine the Levinger constant, which is proportional to the ratio of nuclear photo-absorption to that for photo-disintegration of a deuteron. We extract the Levinger constant based on the ratio of momentum distributions at high relative momentum. We compute momentum distributions evolved under similarity RG (SRG) transformations, where the SRC physics is shifted into the operator as a universal two-body term. The short-range nature of this operator motivates using local-density approximations with uncorrelated wave functions in evaluating nuclear matrix elements, which greatly simplifies the analysis. The operator must be consistently matched to the RG scale and scheme of the interaction for a reliable extraction. We apply SRG transformations to different nucleon-nucleon (NN) interactions and use the deuteron wave functions and Weinberg eigenvalues to determine approximate matching scales. We predict the Levinger constant for several NN interactions and a wide range of nuclei comparing to experimental extractions. The predictions at low RG resolution are in good agreement with experiment when starting with a hard NN interaction and the initial operator. Similar agreement is found using soft NN interactions when the additional two-body operator induced by evolution from hard to soft is included. |
Friday, October 28, 2022 10:54AM - 11:06AM |
EK.00003: Ab initio asymptotic normalizations of 7Be and 7Li states Kenneth M Nollett, Satish Chandran Asymptotic normalization coefficients (ANCs) are crucial parameters for models of direct capture reactions, where they can embody constraints derived from experiment or many-body calculations. Here we report ab initio calculations of ANCs for breakup of 7Be and 7Li states into an alpha particle and a 3He or 3H nucleus using the variational Monte Carlo (VMC) method. Previous VMC calculations of these ANCs required computing the spectroscopic overlap of a state onto a cluster configuration, and then reading the ANC from the long-range tail of the overlap; this was problematic because the tail is difficult to compute well in VMC. Here we compute ANCs from an integral relation that folds the wave function with the short-ranged nucleon-nucleon potential, yielding a short-ranged integral. The resulting ANCs are then based on the most accurately-computed parts of the wave function. We report ANCs for the bound states of 7Be and 7Li, which are important for reactions in the Sun and the Big Bang, as well as partial widths of narrow unbound states. This is the first application of integral relations to cluster-separation ANCs in the quantum Monte Carlo context. |
Friday, October 28, 2022 11:06AM - 11:18AM |
EK.00004: The nature of 9N and 9He low-lying states Joshua Wylie, Simin Wang, Witold Nazarewicz A recent experiment provided the first evidence for 9N, a 5p emitter [1]. Since 9N lies well beyond the proton dripline, questions were raised as to the nature of its states and the states of its mirror nucleus, 9He. Experimental data for 9N suggests that there is a possible 1/2+ state and a 1/2- resonance state at higher energy. Initial comparisons with the mirror nucleus 9He suggested that this 1/2+ was a resonance [2,3], thus the ground state for both nuclei might be a resonance, yet both works may have introduced some artificial binding to stabilize the results. According to our Gamow Shell Model calculations, the 1/2+ state of 9He is a virtual state while in 9N the 1/2+ is a threshold resonant state, similar to the ground state of 10N [4]. |
Friday, October 28, 2022 11:18AM - 11:30AM |
EK.00005: Nuclear short-range correlations using the generalized contact formalism: new results Ronen Weiss The generalized contact formalism (GCF) is a useful model for analyzing the properties and implications of nuclear short-range correlations (SRCs). Based on an asymptotic factorization of the wave function when two-particles are found close to each other, the GCF was used to study two-body densities and momentum distributions, electron scattering reactions, and more, resulting in a consistent and comprehensive picture regarding the effects of SRC pairs. In this talk, I will review some of the main results of the GCF, focusing on recent studies regarding neutrinoless double beta decay matrix elements, the implications of isospin symmetry and more. |
Friday, October 28, 2022 11:30AM - 11:42AM |
EK.00006: Particle-Vibration Coupling Effect on the Nuclear Shell Structure at Finite Temperature Herlik Wibowo, Elena Litvinova In the present work, we investigate the shell evolution of neutron-rich even-even Ni isotopes (A = 68-78) with temperature in a beyond-mean-field framework, where a thermal relativistic mean-field model (RMF) is extended by including the coupling between nucleons and collective vibrations. The single-particle states are extracted by solving the temperature-dependent Dyson equation with the dynamical kernel of the particle-vibration coupling (PVC) origin on the basis of thermal RMF. The toy models in strongly truncated space are utilized to further investigate the sensitivity of the fragmentation pattern to the phonon frequencies, the mean-field level density, and the PVC strength. |
Friday, October 28, 2022 11:42AM - 11:54AM |
EK.00007: Ab initio calculations of Gamow-Teller strength distributions Samuel J Novario, Gaute Hagen, Petr Navratil The progress in ab initio calculations of atomic nuclei can be attributed to advances in chiral effective field theory, many-body methods, and high-performance computing. In particular, electroweak currents derived from chiral effective field theory have made it possible to accurately calculate corresponding phenomena without quenching factors. These phenomena have wide-ranging implications from nucleosynthesis to neutrinoless double-beta decays. In this presentation, I will detail our recent coupled cluster calculations of Gamow-Teller strength functions in several nuclei where we have utilized interactions and full two-body electroweak currents derived from chiral effective field theory. (LA-UR-22-26433) |
Friday, October 28, 2022 11:54AM - 12:06PM |
EK.00008: The anchor-based approach to energy density functional optimization Ahmad Taninah, Anatoli Afanasjev Nuclear density functional theory (DFT) is one of the most widely used theoretical tools for the description of finite nuclei and neutron stars. Its performance is defined by underlying energy density functionals (EDFs) with a few parameters adjusted to the properties of finite nuclei and nuclear matter. A common difficulty in the DFT framework (both relativistic and nonrelativistic) is that the inclusion of the deformed nuclei in the fitting protocols increases the optimization time dramatically. As a result, the absolute majority of EDFs are fitted by employing only spherical nuclei in the fitting protocols. However, while this results in a good description of spherical nuclei, it reduces the global performance of the EDFs [1, 2]. To alleviate this problem, we propose a new anchor-based approach to the optimization of EDFs. In this approach, the optimization is based on a set of "anchor" spherical nuclei. The binding energies of these nuclei are corrected by minimizing the difference between the calculated and experimental binding energies of all known even-even nuclei. To illustrate the approach's applicability, it has been used to optimize the covariant EDFs and has shown significant global improvements in the description of physical observables [2]. In my presentation, I will discuss this new approach and highlight the main results obtained. |
Friday, October 28, 2022 12:06PM - 12:18PM |
EK.00009: Disruption of the Nuclear Standard Model by the QUEST/RING Theory Claude Massot, Olivier Massot
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