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 EF: Nuclear Structure: Light Nuclei I |
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Chair: Mallory Smith, NSCL Room: Berkeley & Clarendon |
Tuesday, October 12, 2021 11:45AM - 11:57AM |
EF.00001: Global Sensitivity Analysis of Collective Observables for Light Nuclei Kevin Becker, Kristina D Launey, Tomas Dytrych Collective motion plays an important role in the dynamics of atomic nuclei across the Segre chart, and ab initio studies show that such features arise from an emergent symmetry in nuclear Hamiltonians [1]. With the goal to constrain uncertainties on collective observables computed with chiral effective field theory interactions, we couple the framework of the symmetry-adapted no-core shell model with the method of global sensitivity analysis [2]. In this talk, we discuss a sensitivity analysis that determines the low-energy constants in the interaction that have the largest impact on collective observables. We generate a sufficiently large sample of unique sets of the low-energy constants, and diagonalize the associated Hamiltonians to obtain the low-lying wavefunctions for selected light nuclei. Specifically, we compute the quadrupole moments and B(E2) transitions for 6Li and 12C. This opens the door for constructing nuclear potentials for precise calculations of collective nuclear observables. |
Tuesday, October 12, 2021 11:57AM - 12:09PM |
EF.00002: Evidence against the Efimov effect in 12C from spectroscopy and astrophysics Jack E Bishop, Grigory V Rogachev, Sunghoon Ahn, Eric Aboud, Marina Barbui, Alexandra Bosh, Joshua Hooker, Curtis Hunt, Heshani Jayatissa, Evgeniy Koshchiy, Rachel Malecek, Scott T Marley, Michael Munch, Emmanuel Pollaco, Cole D Pruitt, Brian T Roeder, Antti Saastamoinen, Lee G Sobotka, Sriteja Upadhyayula The Efimov effect is a universal phenomenon in physics whereby three-body systems are stabilized via the interaction of unbound two-body sub-systems. A hypothetical state in 12C at 7.458 MeV excitation energy, comprising of a loose structure of three α-particles in mutual two-body resonances, has been suggested to correspond to an Efimov state in nuclear physics. Using the combined data sets from two recent experiments, one with the TexAT TPC to measure α-decay and the other with Gammasphere to measure γ-decay of states in 12C populated by 12N and 12B β-decay respectively, we achieve high sensitivity to states in close-proximity to the α-threshold in 12C. In parallel, calculations of the triple-alpha reaction rate show the inclusion of the Efimov state corresponds to a large increase in the reaction rate around 5×107 K. This talk will summarize these results and demonstrate the remarkable sensitivity achieved in this combined approach. |
Tuesday, October 12, 2021 12:09PM - 12:21PM |
EF.00003: Quenching of single-particle strength in A = 15 nuclei. Benjamin P Kay, Jie Chen, Matt D Gott, Calem R Hoffman, Heshani Jayatissa, John P Schiffer, Tsz Leung Tang, Ivan Tolstukhin, Alan J Mitchell, Gareth B Roderick, Heather L Crawford, Augusto O Macchiavelli, Francesc Yasid Ayyad Limonge, Gemma L Wilson, Sam Bennett, Sean J Freeman, Katie Garrett, David K Sharp, Kelly A Chipps, Matthew Hall, Patrick T MacGregor A simultaneous determination of the occupancy of the 1s and 0d orbitals outside of 14C and 14N has been made via the neutron-adding (d,p) reaction in inverse kinematics using the HELIOS spectrometer at Argonne National Laboratory. Spectroscopic factors for these orbitals are found to be about 0.6 that of the single-particle values, indicating a quenching of single-particle motion consistent with a large body of transfer-reaction data. The magnitude of this quenching and its dependence on ΔS, the difference between proton and neutron separation energies, is inconsistent with that seen in intermediate-energy knockout reactions on complex targets. |
Tuesday, October 12, 2021 12:21PM - 12:33PM |
EF.00004: Structure Studies of 13Be Jerome Mathew Kovoor, Joshua Hooker, Marija Vostinar, Kate L Jones, Rituparna Kanungo, Matthias Holl, Orry Workman, Steven D Pain A variety of structure phenomena such as alpha clustering, neutron halos, and the breakdown of the N=8 shell gap are observed in the beryllium nuclei, making them attractive for nuclear structure studies. The structure of 13Be offers insights into the N=8 shell gap, the nature of the Borromean 14Be nucleus, the influence of the continuum, and the nature of neutron-drip line nuclei. |
Tuesday, October 12, 2021 12:33PM - 12:45PM |
EF.00005: Search for 15Be decays to 12Be+3n Anthony N Kuchera, Rida Shahid, Aidan J Edmondson, Jinpai Zhao, Nathan H Frank, Oscar Peterson-Veatch 15Be is an unbound nuclide that has been observed to decay by the emission of a single neutron to the ground state of 14Be. The ground state of 15Be could not be confirmed because of a possible decay at lower energy through an unbound state in 14Be which would emit two more neutrons. The present work is an attempt to search for these decays consisting of 12Be and three neutrons originating from unbound states in 15Be populated via a neutron transfer from a CD2 target to a 14Be beam. This experiment was performed at the National Superconducting Cyclotron Laboratory using the Modular Neutron Array (MoNA) and Sweeper magnet setup to detect the neutrons and charged particles, respectively, from the decays. Using invariant mass spectroscopy, the two-, three-, and four-body decay energies were reconstructed. The data were interpreted by comparing the experimental decay energies to those produced by detailed Monte Carlo simulations. Preliminary results indicate the observation of an unbound state in 15Be constructed from 12Be+3n at a comparable energy to the previously observed state that decays to 14Be+n. |
Tuesday, October 12, 2021 12:45PM - 12:57PM |
EF.00006: Experimental study of near-threshold proton resonances in11B Eilens Lopez Saavedra, Sergio J Almaraz-Calderon, Lagy T Baby, Benjamin W Asher, Ashton B Morelock, Jesus F Perello, Eli S Temanson, Ingo L Wiedenhoever, Anthony N Kuchera, Kirby W Kemper The study of near-threshold proton resonances in 11B has been the object of several recent theoretical and experimental studies due to its unique structural and decay properties. An experiment to search for charge particles decaying from low-lying, low spin resonance states in 11B was performed at the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University,using a radioactive 10Be beam via the 10B(d,n) reaction. The 11B recoils were measured in coincidence with an array of silicon detectors where protons and alpha particles decaying from unbound states in 11B were identified. Details on the experiment and preliminary results will be presented in this work. |
Tuesday, October 12, 2021 12:57PM - 1:09PM |
EF.00007: A Study of the Low-Lying States of 9B with a Super-Enge Split-Pole Spectrograph (SE-SPS) and the Silicon Array for Branching Ratio Experiments (SABRE) Rachel Malecek, Scott T Marley, Catherine M Deibel, Kevin T Macon, Erin C Good, Balakrishnan Sudarsan, Khang H Pham, Keilah S Davis, William D Braverman, Zach Purcell, Ingo L Wiedenhoever, Lagy T Baby, Gordon W McCann, Chris J Esparza, Benjamin W Asher, Eilens Lopez Saavedra, Bryan Kelly, Caleb Benetti, Vignesh Sitaraman, Alex Conley, Ashton B Morelock, Kenneth G Hanselman, Jesus F Perello, Eli S Temanson, Aldo Bonasera We used the single-particle transfer reaction 10B(3He,α) to investigate the structure of the light, neutron-deficient nucleus 9B. Previous studies of 9B report discrepant values for the energy, width, and spin-parity of this isotope’s first-excited state, which is thought to be the mirror of the 1.65-MeV 1/2+ state in 9Be. Experimental results for this state’s energy range between 0.7-1.8 MeV with widths between 0.3-1.5 MeV. We performed the 10B(3He,α) reaction at Florida State University with a 7.5-MeV 3He beam incident on an isotopically enriched 10B target. Alpha particles were momentum-analyzed by the new Super-Enge Split-Pole magnetic spectrograph (SE-SPS) and detected at the focal plane, while the decay particles of 9B were detected by the Silicon Array for Branching Ratio Experiments (SABRE) at backward laboratory angles. Preliminary results from this experiment will be presented. |
Tuesday, October 12, 2021 1:09PM - 1:21PM |
EF.00008: Probing a possible excited state of tritium via the 6He(p,t)α reaction with the TexAT TPC Cody E Parker, Grigory V Rogachev, Dustin P Scriven, Jack E Bishop, Evgeniy Koshchiy, Eric Aboud, Marina Barbui, Alexandra Bosh, Emily Harris, Curtis Hunt, Michael J Roosa, Brian T Roeder, Antti Saastamoinen The 3H nucleus, or triton, is a well-studied few-body system, however, there remains uncertainty as to whether an exited state exists. Two previous experiments studying 6He(p,t)α at single beam energies [JETP Lett 59, 320 (1994); PRC 68, 024602 (2003)] observed an enhancement in the final α-particle spectrum corresponding to an excitation energy of about 7 MeV in the triton. To overcome the limitations of the single-beam energy measurements, the Texas Active Target Time Projection Chamber (TexAT TPC) has been utilized to measure 6He(p,t)α at multiple energy slices along the beam axis at the Texas A&M University Cyclotron Institute. Reconstructing the vertex location, energy deposited, and scattering angle of the outgoing α-particles allows for Q-value reconstruction. When coupled with kinematics, this is used to separate ground state and potential excited state events. The decay products from any potential excited state can also be measured with the TPC to provide an unambiguous reaction identification. The latest results from this work will be presented. |
Tuesday, October 12, 2021 1:21PM - 1:33PM |
EF.00009: Abstract Withdrawn |
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