Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session K12: Nuclear Theory IIIRecordings Available
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Sponsoring Units: DNP Chair: Emanuele Mereghetti, LANL Room: Shubert |
Sunday, April 10, 2022 1:30PM - 1:42PM |
K12.00001: Coarse-Graining of Heavy-Ion Collisions at Fermi Energy Thomas J Onyango, Ralf F Rapp, Aldo Bonasera Heavy-ion collisions aim at exploring the properties of hot and dense nuclear matter. Among the key questions are if and how the produced medium reaches (local) thermal equilibrium enabling the study of generic properties of strongly interacting matter. Here, we utilize a coarse graining method to investigate the kinetic properties of the fireball formed in nuclear collisions at Fermi energies. Based on the output from microscopic transport simulations for nucleon positions and momenta within the Constrained Molecular Dynamics (CoMD) model, we employ fit functions for the single-nucleon momentum distributions and extract the time evolution of local thermodynamic properties, focusing on central collisions of Ca-40 nuclei at 35 AMeV bombarding energy. It turns out that the transverse-momentum distributions are well described by Fermi distributions with a time-dependent temperature and chemical potential. In the longitudinal direction, off-equilibrium effects due to the primordial motion of the incoming nuclei are essential and are accounted for by introducing a two-centroid motion into the distributions. We find that the ``directed" kinetic energy associated with the centroid motion dissipates after about 150fm/c, at which point approximate local thermal equilibrium is reached at temperatures of around 6 MeV. We convert our results into a trajectory in the phase diagram and discuss future applications of calculating photon emission spectra. |
Sunday, April 10, 2022 1:42PM - 1:54PM |
K12.00002: Evolving optical potentials to low resolution Mostofa A Hisham, Anthony J Tropiano, Richard J Furnstahl Similarity Renormalization Group (SRG) operations evolve Hamiltonians by continuous unitary transformations, driving hard potentials to softer potentials by decoupling high- and low-momentum components. In practice the SRG will shift the high-momentum physics in the nuclear wavefunction, such as Short-Range Correlations (SRCs), to reaction operators when calculating nuclear observables such as cross sections. Using a toy model, we examine properties of the optical potential through SRG transformations and study the effects of commonly used approximation methods on the SRG-evolved potential. We also investigate the perturbativeness of such optical potentials by looking at the SRG evolution of the Weinberg eigenvalues of the interaction. Finally, we differentiate the non-locality that arises from SRG evolution from the non-local optical potential itself. |
Sunday, April 10, 2022 1:54PM - 2:06PM |
K12.00003: Irreducible three-body forces in deuteron-nucleus reactions: Faddeev method vs ab initio theory Linda Hlophe, Sofia Quaglioni Deuteron-induced nuclear reactions are typically described within a Faddeev three-body model consisting of a neutron, proton, and the nucleus interacting through pairwise forces. While Faddeev techniques enable the exact description of the three-body dynamics, their predictive power is limited in part by the omission of irreducible three-body nucleon-nucleon-nucleus forces. An alternative approach for describing deuteron-nucleus reactions is ab initio theory, where the system is described from first principles, starting from individual nucleons and the interactions amongst them. We adopt the ab initio no-core shell model (NCSM) coupled with the resonating group method (RGM) to compute microscopic nucleon-nucleus interactions and use them to describe deuteron-induced reactions by means of momentum space Faddeev calculations, beginning with 2H+4He scattering. Simultaneously, we also carry out ab initio calculations of the same deuteron-induced scattering process within the NCSM/RGM approach. I will show that the effects of the irreducible three-body force are not negligible and impact bound state energies as well as cross sections. I will also demonstrate that the irreducible three-body force arises from the complete antisymmetrization of the nucleon-nucleon-nucleus system. This finding paves the way for improved Faddeev calculations of deuteron-nucleus reactions. |
Sunday, April 10, 2022 2:06PM - 2:18PM |
K12.00004: Angular-momentum projection in coupled-cluster theory: structure of 34Mg Thomas Papenbrock, Gaute Hagen, Sam Novario, Zhonghao Sun, Justin G Lietz, Gustav R Jansen, Thomas Duguet, Alexander Tichai Single-reference coupled-cluster theory is an accurate and affordable computational method for the nuclear many-body problem. For open-shell nuclei, the reference state typically breaks rotational invariance and angular momentum must be restored as a good quantum number. We employ the disentangled coupled-cluster formalism and a Hermitian approach for the angular momentum projection. Our results agree with benchmarks and data for 8Be and 20Ne using a two-nucleon interaction from chiral effective field theory and for pf-shell nuclei within a traditional shell model. We predict the rotational band in the exotic nucleus 34Mg. |
Sunday, April 10, 2022 2:18PM - 2:30PM |
K12.00005: Active space coupled cluster calculation of open-shell nuclei Zhonghao Sun, Gaute Hagen, Thomas Papenbrock We present an active space coupled-cluster approach to the calculations of open-shell nuclei. The Hilbert space of the Hamiltonian is split into an active and external space. Cluster operators in the active space are determined through a spherical shell model calculation. The contributions of 4-particle-4-hole excitations adjacent to the Fermi surface are captured, and the rotation invariance of the system is preserved in the active space. The cluster operators in the external space (coupled to the active space) are determined through the standard coupled cluster. We applied the method to the low-lying states of 20Ne and 12C and compared it with the angular momentum projected coupled-cluster calculations. |
Sunday, April 10, 2022 2:30PM - 2:42PM |
K12.00006: Covariant energy density functionals optimization: a new approach. Ahmad Taninah, Anatoli Afanasjev Covariant density functional theory (CDFT) is one of the modern theoretical tools for the description of finite nuclei and neutron stars. Its performance is defined by underlying covariant energy density functionals (CEDFs) which depend on a number of parameters. The analysis of the major classes of CEDFs reveals the existence of parametric correlations between these parameters [1,2]. The removal of these correlations reduces the number of independent parameters to five or six depending on the underlying functional structure without leading to a degradation of the performance of CEDFs on a global scale [2,3]. However, this analysis is based on the fitting protocols that employ only spherical nuclei. The results of this study reveal that information about deformed nuclei should be included in the fitting protocol for improving the performance of CEDFs [3]. Furthermore, an isospin-dependent pairing interaction should be employed to improve performance [3]. This presentation will provide details of the new method and highlight the main results. |
Sunday, April 10, 2022 2:42PM - 2:54PM |
K12.00007: Lattice QCD Determination of the Bjorken-π₯ Dependence of PDFs at Next-to-next-to-leading Order Xiang Gao, Andrew D Hanlon, Swagato Mukherjee, Peter Petreczky, Philipp Scior, Sergey Syritsyn, Yong Zhao In this talk, we present a direct calculation of the π₯-dependence of pion valence PDF with the large-momentum effective theory approach. In this calculation we adopt the most up-to-date theoretical developments on the systematic corrections, which include the hybrid renormalization scheme that rigorously renormalizes the lattice matrix elements at both short and long distances, as well as the two-loop matching kernel that allows for direct calculation of the π₯-dependence of the PDF without any model assumption. Therefore, we are able to make predictions for the PDF at π₯β[π₯min,π₯max] where the systematic uncertainties are under control, which is a firm step towards precision-controlled calculation. |
Sunday, April 10, 2022 2:54PM - 3:06PM Withdrawn |
K12.00008: Quest Ring Theory to extract nuclear inner energies Claude Massot
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Sunday, April 10, 2022 3:06PM - 3:18PM |
K12.00009: On Using Controllable Mass Objects to Induce Linear Motion on Staionary Systems Matthew Gorban, William Julius, Gerald B Cleaver In a Gedanken experiment, we previously demonstrated that, by carefully changing the mass of an object undergoing 1D harmonic motion, an otherwise stationary system can undergo induced linear motion over the course of a complete harmonic cycle. Here we expand upon this result and consider the effects of isolated versus coupled mass exchange between two controllable mass objects in a two-mass spring system. Additionally, we analyze the effects of locally changing an object's mass and address necessary conditions for setting up a quantum system that incorporates vacuum symmetry breaking to induce bulk motion in harmonic quantum system. |
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