Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session M10: Nuclear Theory III |
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Chair: Amy Lovell, Los Alamos Natl Lab Room: Hilton Waikoloa Village Kohala 3 |
Friday, December 1, 2023 2:00PM - 2:15PM |
M10.00001: Abstract Withdrawn
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Friday, December 1, 2023 2:15PM - 2:30PM |
M10.00002: Uncertainty-quantified optical potentials for the fission fragment region Kyle Beyer, Amy E Lovell, Cole D Pruitt, Brian Kiedrowski Fission fragments present a messy but unique source of experimental data about the many-body physics of neutron-rich nuclei, which has implications in astrophysical nucleosynthesis, energy, and nuclear non-proliferation applications. Currently, phenomenological optical potentials, the nucleon-nucleus interactions used in nuclear reaction models, are calibrated to direct reaction experiments on stable targets, and extrapolated away from stability for applications involving neutron-rich nuclei - including in fission event generators that use Hauser-Feshbach fragment de-excitation, such as CGMF, FIFRELIN, GEF, and Meitner. The goal of this work is to outline the inclusion of compound-nuclear observables - with fission as a case study - into the calibration of these optical potentials, using a Monte Carlo Hauser-Feshbach approach. To make this model calibration computationally tractable, while preserving event-by-event correlations in observables, an intrusive model order reduction technique for calculating transition matrices is constructed using the reduced basis method, with preliminary results showing a speedup on the order of 10^3. Initial results indicate the presence of hitherto untapped constrains on optical potentials in neutron-fragment correlated fission experiments, especially neutron energy spectra as a function of fragment mass and TKE. The overarching goal is to construct the world's first uncertainty-quantified optical potential for the fission fragment region that is simultaneously calibrated to direct reactions on isotopes in this region, as well as experimental fission observables. |
Friday, December 1, 2023 2:30PM - 2:45PM |
M10.00003: Noniterative finite amplitude methods for E1 and M1 transitions and the application to neutron radiative capture cross sections Hirokazu Sasaki, Toshihiko Kawano, Ionel Stetcu We derive the equation of quasiparticle random-phase approximation (QRPA) based on noniterative finite amplitude method and demonstrate how the fully microscopic density functional theory predicts the electric dipole (E1) and the magnetic dipole (M1) giant resonances. The obtained photoabsorption cross sections are applied to the calculation of neutron radiative capture cross sections based on the statistical Hauser-Feshbach theory. We find that the low energy M1 scissors mode in our QRPA calculation can significantly enhance the capture cross sections for deformed nuclei. |
Friday, December 1, 2023 2:45PM - 3:00PM |
M10.00004: Connecting structure of nuclei to nucleon-nucleus scattering Aaina Thapa, Emanuel Chimanski, Jutta E Escher, Walid Younes, Sophie Péru, Eunjin In Charged-particle inelastic scattering is an experimental probe for excitation spectrum of the target nucleus and has applications in surrogate reaction method. On the other hand, the experimental data for neutron-nucleus inelastic scattering is scarce and thus one needs a robust theoretical framework to study it in a predictive way. To this end we integrate microscopic structure of nuclei with reaction theory for nucleon-nucleus scattering. We implement the Jeukenne, Lejeune, Mahaux (JLM) semi-microscopic folding approach [1,2,3], where the medium effects on nuclear interaction are parameterized in nuclear matter to obtain nucleon-nucleon interaction in a medium at positive energies. We solve the nuclear ground state using Hartree-Fock-Bogoliubov many-body method, and by approximating interaction between nucleons within a nucleus as Gogny-D1M potential [4]. The vibrational excited states of the target nucleus are calculated using quasi-particle random phase approximation method [5]. In this presentation, we present our results for elastic and inelastic scattering cross sections for the chain of Zr isotopes using this approach. |
Friday, December 1, 2023 3:00PM - 3:15PM |
M10.00005: Inelastic Reactions on a Quantum Computer Gautam Rupak, Paulo F Bedaque, Ratna Khadka, Muhammad Yusf Radiative processes, where a photon/neutrino is emitted, play an important role in atomic, nuclear, and particle physics. I present an algorithm for calculating radiative, and in general inelastic processes such as charge exchange reactions, on a quantum computer. The algorithm relies on an extra qubit that, in a certain sense, represents the photon/neutrino. It is used to drive the system near a resonance of the Rabi oscillations between initial and final states. The transition matrix elements are related to the frequency of the oscillations. We demonstrate the feasibility of the method by performing actual quantum computations and simulations of simple systems. |
Friday, December 1, 2023 3:15PM - 3:30PM |
M10.00006: Reclassifying neutron resonance spins with Machine Learning Gustavo P Nobre, David A Brown, Ethan Richards, Pedro Rodríguez, Sophia J Hollick, Sergey Scoville, Mary Fucci Neutron resonances are sharp fluctuations seen in neutron transmission and capture experiments at low-energy neutron-induced reactions. Properties of neutron resonances are some of the few experimental constraints to nuclear level densities and gamma strength functions (crucial for modeling many nuclear applications). Resonances are characterized by their angular momenta quantum numbers, which are normally assigned through fits often done in a not fully reproducible manner. Comprehensive compilations of evaluated resonances often contain incorrectly assigned spins. To address these issues, we developed and successfully applied a Machine-Learning method [1] to train a multi-label classifier to identify resonances with incorrect spin assignments. Model training can be done either on synthetic data built to simulate statistical properties of resonances seen in real nuclei, or on ranges of real experimental data known to have reliable assignments . The trained classifier can be applied to resonances sequences from compiled, evaluated, or experimental data. We will show results on 52Cr and 238U using synthetic and/or real data to train, cross-validate and predict spin assignments on evaluated data. We will also discuss future developments. |
Friday, December 1, 2023 3:30PM - 3:45PM |
M10.00007: Revising Neutron Capture Gamma Ray Production Emanuel V Chimanski, Bret R Beck, Lee A Bernstein, David A Brown, Roberto Capote, Godfree Gert, Aaron M Hurst, Caleb Mattoon, Elizabeth McCutchan, Chris Morse, Gustavo P Nobre, Shuya Ota, Andrej Trkov The gamma-ray spectrum produced by neutron induced reactions is utilized to reveal the microscopic features of the nucleus. The characteristics of the emitted photons are in important component in various modern applications, including the active interrogation technique used in planetary space science and oil well logging. The gamma-ray production information is compiled in evaluated nuclear data files, enabling a precise transport simulation and the success of material interrogation procedures. We are aware of deficiencies and gaps in accessible nuclear data libraries, as well as the need to enhance coincidence measurement applications. The deficiencies affect both secondary gamma emission and correlations between deexcitations and neutron emissions. One of our goals is to support the particle-gamma and gamma-gamma coincidence modeling by revising the gamma production data and formats within ENDF/B-VIII.0. Our efforts are intended to improve simulation performed with different transport codes e.g. MCNP, GEANT4, and Mercury. In this context, we are improving capture and inelastic gamma-ray libraries. In this work, we'll discuss a selection of refined thermal neutron capture gamma-ray spectrum for light nuclei. An in-line gamma cascade capability for both primary gammas and secondary cascade emissions will also be discussed. |
Friday, December 1, 2023 3:45PM - 4:00PM |
M10.00008: Effect of the Coulomb force on fission fragment angular momenta Jorgen Randrup Nuclear fission produces fragments endowed with typically half a dozen units of angular momentum each. After scission has occurred and the fragments recede, they are still interacting via the Coulomb force which exerts an undulating but steadily decreasing torque on deformed fragments. This may lead to an amplification of their rotations, in effect shifting the fragment spin distributions upwards by 1-2 units. Complete dynamcial calculations are carried out to illustrate the effect quantitatively, but its essential features can be understood by perturbative considerations. |
Friday, December 1, 2023 4:00PM - 4:15PM |
M10.00009: Construction of conserved covariant current operators in phenomenological relativistic quantum models of strongly interacting systems. Wayne N Polyzou I discuss a systematic method for constructing conserved covariant current operators that are consistent with the dynamics in phenomenological relativistic models of strongly interacting systems. The current is constructed by expressing the Hamiltonian in the Weyl representation, replacing the momentum operators by gauge covariant derivatives, and extracting the coefficient of the part of the operator that is linear in vector potential. The method generates the representation-dependent many-body parts of the current operator that are needed in order to satsify the dynamical constraints of current covaraince and current conservation. Because the resulting current is an operator, it can be consistently applied to different reactions. Non-commuting operators are treated explicitly using Trotter methods. |
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