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 CL: Nuclear Theory I |
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Chair: Wataru Horiuchi, Hokkaido University Room: Hilton Queen's 5 |
Wednesday, October 24, 2018 7:00PM - 7:15PM |
CL.00001: Nucleon-nucleon interaction charge dependence in Nd breakup within effective “isospinless” model Vladimir M Suslov, Igor Filikhin, Branislav Vlahovic The role of the total isospin 3/2 component in three-nucleon reactions was studied in [1], based on the standard isospin formalism. The component has to be taken into account to describe the effect of the charge-independence breaking (CIB) in nucleon-nucleon interaction. We propose alternative approach based in ''given charge formalism'' which includes the isospin 3/2 component in a natural way, assuming the neutrons and protons to be distinguishable particles. We developed the effective “isospinless” model for the three-nucleon systems based on the given charge formalism. The charge symmetry breaking (CSB) effect for 3He and 3H is simulated by using s-wave MT-I-III potential with adjusted parameters. The calculated energy difference between the 3He and 3H, caused by the CSB, is well consistent with previous evaluations. The isospin and “isospinless” models are applied to simulate the CIB effect for the Nd breakup scattering at low energy. We have shown that the obtained results weakly depend on CIB taken into account. However, the corrections are noticeable on the background of possible numerical inaccuracy. [1] H. Witala, et al. Few-Body Syst. 57, 1213 (2016). |
Wednesday, October 24, 2018 7:15PM - 7:30PM |
CL.00002: Three-body correlations in exotic-atom-like three- and four-bosons Hajime Moriya, Wataru Horiuchi An exotic atom is defined as a Coulomb bound system that includes particles other than nucleons or electrons, e.g., an atomic system including mesons. In particular, exotic atoms with anti-$K$-meson ($\bar{K}$) have been focused on from interest in understanding the interaction between an $\bar{K}$ and a nucleon ($\bar{K}N$ interaction). The $\bar{K}N$ interaction is known to be short-range and strongly attractive, which predicts nuclear deeply bound states consisting of $\bar{K}$ and nucleons. However, the existence of those states is still under discussion and we need further investigation on such systems. The present study discusses the relationship between the nuclear and atomic bound states in the exotic-atom-like systems with respect to the strength of the two-body interaction. For simplicity we first consider a simple model consisting of identical bosons whose interaction has long-range and short-range attraction parts. We investigate changes of the binding energy of the three-body system with varying the strength of the short-range attraction, and quantify the evaluation of the three-body correlations in the three- and four-body systems. |
Wednesday, October 24, 2018 7:30PM - 7:45PM |
CL.00003: Novel method for computing the tensor multipole expansion of two nucleon currents in momentum space. Kyle Wendt Two nucleon currents are a critical ingredient in predictive calculations of electroweak phenomena in nuclei such as beta-decay, neutrino-nucleus scattering, and neutrinoless double beta decay. However, their complicated mathematical structure has rendered these currents prohibitively difficult to include in modern basis-expansion many-body approaches, such as coupled cluster theory or in-medium similarity renormalization group, without severe approximations. We have developed a novel method to compute and represent the multipole expansion of these currents in mixed momentum-spline partial wave basis. We will present an overview of the formalism as well preliminary results using the full/non-approximated momentum dependence of the current. |
Wednesday, October 24, 2018 7:45PM - 8:00PM |
CL.00004: Nuclear Few-Body Problem with Chiral Perturbation Theory Md Kamrul Hoque Ome, Michael McNeil Forbes, Jeremy Holt Lattice Quantum Chromodynamics (LQCD) provides a method to connect QCD with low-energy phenomena, but calculations are limited to small boxes which make it difficult to extrapolate to large distances. In this talk, I shall discuss techniques for solving Schr\"{o}dinger equation in boxes for non-local chiral potentials to facilitate the extraction of physical parameters from lattice QCD. For example, I shall discuss how discrete variable representation basis with periodic and twisted boundary conditions can improve computational efficiency. I shall also discuss the advantages of twist-averaged boundary conditions for solving problems in computational lattice QCD. |
Wednesday, October 24, 2018 8:00PM - 8:15PM |
CL.00005: Scalar, axial and tensor matrix elements in light nuclei from lattice QCD William Detmold I will discuss recent calculations of the matrix elements of scalar, axial and tensor quark bilinear operators in light nuclei at unphysically heavy values of the quark masses. Axial matrix elements control the Gamow-Teller decays of nuclei and have potential for precision tests. Tensor matrix elements determine the quark chromo-electric dipole moment and are important in the context of proposed experiemnts to meaure nuclear EDMs. Scalar matrix elements are important for interpretation of dark matter direct detection experiments. Our calculations provide a full flavour decomposition of the matrix elements in A=1,2,3 nucleon system. Nuclear effects are resolved in most channels, with axial and tensor matrix elements modified at the percent level from naive expectations. In contrast, the scalar matrix elements in the nuclei differ at the 10% level from scaling those of the nucleon. If these effects persist at the physical quark masses and for larger, experimentally practical nuclei, their phenomenological impat would be significant. |
Wednesday, October 24, 2018 8:15PM - 8:30PM |
CL.00006: Similarity Renormalization Group Evolution of Many-body Operators Peter Gysbers, Petr Navratil, Sofia Quaglioni Unitary transformations such as Similarity Renormalization Group (SRG) are used to soften nuclear interactions to improve convergence in the calculation of nuclear wavefunctions and energies. Calculations of other observables will only be correct if the corresponding operators are also transformed. I will present applications of SRG to nuclear radii, Gamow-Teller beta decay and neutrinoless double-beta decay operators. By performing the transformation in two- or three-body space, the SRG-induced two- and three-body contributions can be separated and analyzed. |
Wednesday, October 24, 2018 8:30PM - 8:45PM |
CL.00007: Ab initio calculation of electromagnetic observables in the p-shell using translationally-invariant intrinsic operators Patrick J Fasano, Mark A Caprio, Pieter Maris, James P Vary Ab initio methods in nuclear theory strive to make quantitative predictions of nuclear observables, starting with the internucleon interaction. In the no-core configuration interaction (NCCI) approach, calculations have traditionally been performed with harmonic oscillator functions and Nmax truncation due the factorizability into center-of-mass and intrinsic wave functions. Use of other bases and truncations (which may have, e.g., better asymptotics or convergence behavior) induces a mixing between these degrees of freedom which contaminates observables calculated using one-body operators. By using translationally-invariant two-body operators in place of their one-body counterparts, we compute electromagnetic observables in the p-shell using other single-particle orbitals, such as natural orbitals, and many-body truncation schemes. |
Wednesday, October 24, 2018 8:45PM - 9:00PM |
CL.00008: Electromagnetic sum rules for the no-core shell model Calvin Johnson Sum rules provide a simple characterization of transition strengths. I present systematic results for E2, M1, and E1 transitions in no core shell model calculations. In particular, by calculating sum rules for hundreds of states, I will address the generalized Brink-Axel hypothesis in ab initio calculations. |
Wednesday, October 24, 2018 9:00PM - 9:15PM |
CL.00009: Electromagnetic sum rules and response functions from an ab initio symmetry-adapted framework Robert B Baker, Kristina D Launey, Nir Nevo Dinur, Sonia Bacca, Jerry P Draayer, Tomas Dytrych We will discuss recent work to combine the ab initio symmetry-adapted no-core shell model (SA-NCSM) with the Lorentz integral transform method in order to study the underlying dynamic properties of intermediate mass nuclei from first principles. The SA-NCSM employs realistic interactions and can handle ultra-large model spaces in nuclei up through the calcium region by utilizing symmetries known to dominate the nuclear dynamics. Coupling with the Lorentz integral transform method allows us to calculate electromagnetic sum rules and response functions for nuclei beyond the reach of other methods. We will present benchmark calculations for He-4, compared to the exact solutions of the hyperspherical harmonics method, as well as preliminary electromagnetic response functions obtained in this approach. |
Wednesday, October 24, 2018 9:15PM - 9:30PM |
CL.00010: Linear response on a Quantum Computer Alessandro Roggero, Joseph A Carlson The dynamic linear response of a quantum system is critical for understanding both the structure and dynamics of strongly-interacting quantum systems, including neutron scattering from materials, photon and electron scattering from atomic systems, and electron and neutrino scattering by nuclei. |
Wednesday, October 24, 2018 9:30PM - 9:45PM |
CL.00011: Decoupling of bound states with the Magnus expansion and the in-medium similarity renormalization group Anthony J Tropiano, Scott Bogner, Dick Furnstahl, Nathan M Parzuchowski The in-medium similarity renormalization group (IMSRG) softens nucleon-nucleon interactions by applying a continuous unitary transformation to the Hamiltonian to decouple low- and high-momentum scales. Here we study differences between evolving nuclear Hamiltonians with the typical IMSRG approach and with the Magnus expansion by applying these approaches to a leading-order nucleon-nucleon potential in momentum space that features a spurious, deep bound state at higher chiral effective field theory cutoffs. We consider both the Wegner and relative kinetic energy SRG generators. We find that the Magnus implementation converges to the typical SRG approach. With the Wegner SRG generator, the Magnus expansion can be used to soften nuclear potentials without shifting deeply bound states in the low-energy scale, and the SRG flow equations can be solved with a crude ODE solver without loss of accuracy in the eigenvalues of the evolved operator. |
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