Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session DM: Nuclear Theory I |
Hide Abstracts |
Chair: Amy Nicholson, UNC Room: White Hill |
Tuesday, October 12, 2021 9:30AM - 9:42AM |
DM.00001: Renormalization of pion exchange in nuclear interactions Thomas Papenbrock, Andreas Ekstrom, Gaute Hagen We revisit the renormalization of one- and two-pion exchange and determine the counter terms that are needed to achieve RG invariance. A simple picture emerges, and three-nucleon forces enter at leading order. |
Tuesday, October 12, 2021 9:42AM - 9:54AM |
DM.00002: Fast and rigorous constraints on chiral three-nucleon forces from few-body observables Sarah Wesolowski, Isak Svensson, Andreas Ekstrom, Christian Forssen, Richard J Furnstahl, Jordan A Melendez, Daniel R Phillips We explore the constraints on the three-nucleon force (3NF) of chiral effective field theory (ChiEFT) that are provided by bound-state observables in the A=3 and A=4 sectors. Our statistically rigorous analysis incorporates experimental error, computational method uncertainty, and the uncertainty due to truncation of the ChiEFT expansion at next-to-next-to-leading order. A consistent solution for the 3H binding energy, the 4He binding energy and radius, and the 3H beta-decay rate can only be obtained if ChiEFT truncation errors are included in the analysis. All of these except the beta-decay rate give essentially degenerate constraints on the 3NF low-energy constants, so this observable is crucial for estimating these parameters. We use eigenvector continuation for fast and accurate emulation of No-Core Shell Model calculations of the few-nucleon observables. This facilitates sampling of the posterior probability distribution, allowing us to also determine the distributions of the parameters that quantify the truncation error. We find a ChiEFT expansion parameter of Q=0.33 +/- 0.06 for these observables. |
Tuesday, October 12, 2021 9:54AM - 10:06AM |
DM.00003: Aspects of Three-Nucleon Systems in Pionless Effective Field Xincheng Lin Pionless effective field theory provides a systematic and model-independent way to study three-nucleon systems, such as neutron-deuteron scattering [1] and the triton [2], at very low momenta (p< m_π, where m_π ≈140 MeV is the pion mass). Calculations of observables at such low momenta are important to the study of big bang nucleosynthesis, some dark matter detection experiments, and some experiments at Triangle Universities Nuclear Laboratory/High Intensity Gamma-ray Source. In this talk, I will present some recent progress in these areas. |
Tuesday, October 12, 2021 10:06AM - 10:18AM |
DM.00004: Calculation of the A=6 bound states within the hyperspherical harmonic basis Alex Gnech, Laura Elisa Marcucci, Michele Viviani, Rocco Schiavilla We present some recent results of the application of the Hyperspherical Harmonic (HH) approach to A=6 nuclei. The use of a new computational approach permitted the extension of the HH method, successfully used by the Pisa in the few-body system context, to study larger systems. We will shortly review some of the technical improvements and then we will show the results for the spectra of the A=6 nuclei computed with modern SRG evolved two-body chiral interactions. Moreover, we will present also some preliminary study where the three-body intractions are added. Finally, we will show a first application of the HH approach technique that we are studying for solving scattering states for A>4. In this presentation, we will try to demonstrate that the HH appproach can reach the same level of accuracy obtained by the mostly used No-Core-Shell-Model method also beyond the few-body sector. |
Tuesday, October 12, 2021 10:18AM - 10:30AM |
DM.00005: A Perturbative Study of the Uncoupled P-Wave Channels for Two-Nucleon Scattering Jaber Balal Habashi The uncoupled P-wave channels of two-nucleon scattering are studied perturbatively from the perspective of effective field theories (EFTs). In this talk I discuss an EFT for these channels that includes a perturbative dibaryon field and perturbative pions. The results of the next-to-next-to-leading order EFT show a good agreement with the Nijmegen partial wave analysis for momenta up to k_{cm} ~ 400 MeV. |
Tuesday, October 12, 2021 10:30AM - 10:42AM |
DM.00006: Finite volume effective field theory for few-nucleon systems William Detmold, Phiala E Shanahan Pionless effective field theory in a finite volume (FVEFT) is investigated as a framework for the analysis of multinucleon spectra and matrix elements calculated in lattice QCD (LQCD). By combining FVEFT with the stochastic variational method, the spectra of nuclei with atomic number A∈{2,3} are matched to existing finite-volume LQCD calculations. Based on the variational wave functions that are constructed in this approach, the finite-volume matrix elements of various local operators are computed in FVEFT and matched to LQCD calculations of the corresponding QCD operators in the same volume, thereby determining the relevant one- and two-body effective field theory counterterms and enabling an extrapolation of the LQCD matrix elements to infinite volume. As examples, the scalar, tensor, and axial matrix elements are considered, in addition to the magnetic moments and the isovector longitudinal momentum fraction. |
Tuesday, October 12, 2021 10:42AM - 10:54AM |
DM.00007: Volume dependence of charged-particle bound states Hang Yu, Sebastian Koenig, Dean J Lee Simulating a quantum system in a finite volume is a powerful theoretical tool to extract information about it. The pioneering work of Lüscher has shown that the real-world properties of the system are encoded in how its discrete energy levels change with the size of the volume, and many aspects of this idea have already been studied. The approach is commonly used for example to analyze lattice calculations of atomic nuclei. We consider the finite-volume correction to the binding energy of two-body systems with a repulsive Coulomb interaction. The long-range nature of the Coulomb interaction constitutes an interesting challenge for the formalism, which normally assumes the presence of short (or finite) range interactions only. We investigate this problem in one and three-dimensional periodic boxes and show that the challenge can be overcome by truncating the Colomb potential at the box boundary. This approach then yields analytic expressions for the volume dependence of bound states in terms of Whittaker functions, which reduce to known results in the limit where the Coulomb interaction is switched off. We test our results against numerical calculations and show how the method can be used to extract asymptotic normalization coefficients for charged-particle bound states. |
Tuesday, October 12, 2021 10:54AM - 11:06AM |
DM.00008: △-full chiral effective field theory in finite harmonic oscillator basis Aaina Bansal, Ragnar Stroberg We regulate △-full chiral effective field theory (EFT) potentials upto next-to-next-to-leading order by using finite harmonic oscillator basis as the regulator. We extend the method, previously developed for pionless effective field theory, to include additional pion-exchange terms between two- and three-nucleons in chiral EFT. This approach ensures ultra-violet (UV) convergence by construction without the need of starting from a big enough oscillator model space to capture the tail of conventionally employed momentum space regulators. The low-energy coefficients of the short-range nucleon-nucleon (NN) and three-nucleon EFT interactions are adjusted to reproduce the low-energy NN phase shifts and triton ground state properties, respectively. We compute the ground state energies and radii of 3H, 3He and 4He nuclei as proof-of-principle calculations for this framework. |
Tuesday, October 12, 2021 11:06AM - 11:18AM |
DM.00009: Chiral Effective Field Theory Parameter Estimation Using Markov Chain Monte Carlo Jason Bub, Maria Piarulli, Saori Pastore Effective field theories (EFTs) offer a rigorous connection of quantum chromodynamics to the low energy regime of nuclear structure and interactions. While high-quality effective interactions have been produced that can successfully replicate experimental data, they suffer from the same shortcoming that plagues much of theoretical nuclear physics: a lack of error estimation. While rough estimates have been used to quantify uncertainties in the models, rigorous and systematic uncertainty quantifications are currently still missing. To remedy this, we introduce an implementation of Markov Chain Monte Carlo (MCMC) to sample from the EFT parameter space. This allows for the quantification of uncertainties on the parameters of the EFT through their probability distributions. We further show that the uncertainty in the EFT parameters can be used to estimate the error in observable calculations through the samples produced. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700