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 D10: Nuclear Structure II |
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Chair: Aaron Gallant, Lawrence Livermore Natl Lab Room: Hilton Waikoloa Village Kohala 3 |
Wednesday, November 29, 2023 9:00AM - 9:15AM |
D10.00001: Half-life measurement of isomeric state in 25Si Daiki Nishimura, Mitsumori Fukuda, Mei Amitani, Chihaya Fukushima, Takuji Izumikawa, Atsushi Kitagawa, Mototsugu Mihara, Eri Miyata, Yuki Nakamura, Takashi Ohtsubo, Takeshi Suzuki, Maya Takechi, Masaomi Tanaka, Takayuki Yamaguchi The rapid proton capture process (rp process) passing through proton-rich nuclei plays an important role in the nucleosynthesis as well as the rapid neutron capture process. However, a possible path of the rp process 24Al(p,γ)25Si(p,γ)26P(p,γ)27S has not been well studied yet due to lack of experimental data for their nuclear structure. Since the temperature in the candidate of the site of rp process is around 109 K, low-lying excited states can affect the rp process taking into account the Maxwell-Boltzmann distribution. The first excited state at 40 keV in 25Si, which is a candidate for the isomer, has not been researched yet in detail. To measure the half-life of the first excited state in 25Si, the γ-ray spectroscopy have been performed at QST-HIMAC. |
Wednesday, November 29, 2023 9:15AM - 9:30AM |
D10.00002: Spectroscopy of 12Be using TexAT-TPC Michael J Roosa, Grigory V Rogachev, Gregory Christian, Marina Barbui, Jack E Bishop, Emily Harris, Evgeniy Koshchiy, Zifeng Luo, Shuya Ota, Cody E Parker, Dustin P Scriven The detailed spectroscopic data that can be extracted from single nucleon transfer reactions provides a useful experimental probe of nuclear structure. This work aims to complement existing data for the 12Be system by measuring the spectroscopic factors to low-lying states in 12Be with the 13B(d,3He)12Be reaction in inverse kinematics. Data for this measurement was taken last fall (F22) using the k500 cyclotron and the Momentum Achromat Recoil Spectrometer (MARS) at Texas A&M University Cyclotron Institute. A 13B beam was impinged on a deuterated methane target and - using the Texas Active-Target Time Projection Chamber - particle tracks and energies were recorded . By reconstructing reaction vertices and tracks in TexAT, angular cross sections and thus spectroscopic factors can be extracted. Ongoing analysis and preliminary results will be discussed. |
Wednesday, November 29, 2023 9:30AM - 9:45AM |
D10.00003: Search for the proposed near-threshold proton-emission resoance in 11B and its implication on βp decay from 11Be Wanpeng Tan, Nicholas Raden, Kevin Lee, Ani Aprihamian, Carl R Brune, Bikash Chauhan, Sydney D Coil, Richard J deBoer, Michael Jeswald, Shelly R Lesher Unusually large decay branching ratio for beta-delayed proton emission from the halo nucleus 11Be was first observed indirectly through detection of the final state nucleus 10Be using the accelerator mass spectroscopy technique. Direct observation of proton emission was claimed by a radioactive beam measurement at TRIUMF with the AT-TPC device, showing evidence of a possible new near-threshold resonance at excitation energy of 11.425 MeV in 11B. Other evidence of such a resonance was also shown in two other different radioactive experiments. However, a recent experiment via 10Be(d,n) uing the neutron time-of-flight technique find no evidence of its existence. At Notre Dame, we conducted a relative simple stable beam experiment to search for this propopsed resonance, by scaning the excitation energy range in 11B through two channels of 7Li(a,a) and 7Li(a,p) to populate near-threshold levels in 11B. The time-of-flight technique was used to separate different particle species and angular distributions from 20 to 150 degrees in the lab frame were measured. Preliminary results will be reported and its implication on possible new physics will also be discussed. |
Wednesday, November 29, 2023 9:45AM - 10:00AM |
D10.00004: Search in the 7Li(α, α)7Li reaction for the Jπ = ½+ near-threshold resonance of 11B relevant to the β-delayed proton emission of 11Be Tianxudong Tang A narrow near-threshold proton emission resonance in 11B (Ex = 11.4MeV, Jπ = ½+) was observed in three independent experiments (Triumf Canada, FRIB, and Florida State University). The theoretical effort showed that coupling to the continuum is important. More experimental information is needed to understand its characteristics. The resonant elastic scattering experiment 10Be(p, p)10Be indicated a decay to the 7Li +α channel. An experiment was conducted at the tandem facility of Notre Dame using Silicon detectors to study this 7Li +α channel of 11B via the 7Li(α, α)7Li reaction. R-matrix was used to analyze the elastic and inelastic scattering excitation functions. This and other recent results will be discussed. |
Wednesday, November 29, 2023 10:00AM - 10:15AM |
D10.00005: Locating the first p1/2- state in 13Be Xinyi Wang, Paul Gueye, Thomas Baumann, Paul A Deyoung, Nathan H Frank, Anthony N Kuchera, Belen Monteagudo Godoy, Thomas Redpath, Henry S Webb, James A Brown Spectroscopy of the neutron unbound 13Be is key to understanding the unexpected structural changes of neutron-rich nuclei around N=8. Invariant mass spectra from previous experiments have not been able to determine the 1/2- p-wave location. This resonance is expected to strongly decay into a long-lived 02+ state in 12Be with a mean lifetime of 331(12) ns. Its decay scheme has a 20% branch through 12Be(2+) into the ground state by emitting a 2.1 MeV gamma ray, and 80% for an E0 transition emitting two 511 keV gamma rays from positron annihilation. An experiment was performed by the MoNA Collaboration at the National Superconducting Cyclotron Laboratory of Michigan State University to study the decay of 13Be by one neutron emission into this isomeric state in 12Be. It consisted of the first usage of a dedicated new telescope made of a stack of 5 silicon detectors and a CsI stopping detector to identify the 12Be fragment. 96 modules of the MoNA-LISA neutron array were used as well as the gamma ray detector CAESAR that was placed around the telescope to detect the decay of the expected isomeric state with long lifetime in the daughter nucleus. This experiment also tested the possibility for sweeperless experiments for the MoNA Collaboration. An overview and preliminary results of the experiment will be presented and discussed. |
Wednesday, November 29, 2023 10:15AM - 10:30AM |
D10.00006: Beta Delayed Spectroscopy of 29F, observation of the first excited state of 29Ne James Christie, Miguel Madurga, Zhengyu Xu, Robert Grzywacz, Philipp Wagenknecht, Thomas T King, Shree Neupane, Joseph Heideman, Aaron Chester, Andrea Richard, Kevin Siegl, James M Allmond, Rin Yokoyama, Jesse N Farr The island of inversion around 32Mg, characterized by tensor-force-driven deformation, has |
Wednesday, November 29, 2023 10:30AM - 10:45AM |
D10.00007: First beta-delayed neutron spectroscopy of doubly-magic $^{24}O$. Shree Neupane, Noritaka Kitamura, Zhengyu Xu, Robert Grzywacz, Joseph Heideman, Thomas T King, Miguel Madurga, Kevin Siegl, Philipp Wagenknecht, Andrea Richard, Aaron Chester Located at the neutron drip-line, $^{24}O$ is the heaviest doubly-magic isotope of the oxygen isotopic chain. As the $Q_eta$ value increases and the neutron separation energy in the daughter nucleus decreases for the neutron-rich nucleus, beta-delayed neutron emission becomes a dominant decay mode, and neutron energy measurement is vital in studying the beta decay to the neutron unbound states. Also, spectroscopy of such drip-line nuclei may provide important information regarding the effects of nuclear interactions and many-body correlations in determining the limits of nuclear stability [1]. |
Wednesday, November 29, 2023 10:45AM - 11:00AM |
D10.00008: Experimental test of the ratio method to constrain the halo property of 11Be with BlueSteAl Shuya Ota, Pierre Capel, Gregory Christian, Kris Hagel, Emily Harris, Zifeng Luo, Elizabeth McCutchan, Chris Morse, Brian T Roeder, Michael J Roosa, Antti Saastamoinen, Dustin P Scriven A new method to constrain the properties of neutron-halo nuclei, the ratio method, was experimentally studied. The ratio method theoretically predicts that it is possible to constrain the single-particle state and the binding energy of a neutron-halo nucleus from the ratios of neutron breakup and elastic cross sections. We, therefore, tested the method to verify the predictions using a well-studied halo nucleus, 11Be, and explored the possibility of further extending the method to more exotic halo nuclei in the future. We measured angular differential elastic and neutron breakup cross sections of 11Be on 12C at 22.5 MeV/u at the Texas A&M University K500 cyclotron. The 12C target was bombarded with a 11Be beam produced at MARS (Momentum Achromat Recoil Separator) spectrometer. Elastic 11Be and neutron breakup 10Be were detected with the BlueSTEAl Si detector array that we developed recently. We will present preliminary results from our experiment. |
Wednesday, November 29, 2023 11:00AM - 11:15AM |
D10.00009: Measurement of (4He, 6Li) Proton-neutron Pair Transfer Reaction for the Study of Proton-neutron Pair Condensation Jiawei CAI, Shinsuke Ota, Masanori Dozono, Satoshi Adachi, Shutaro Hanai, Yuto Hijikata, Genki Hosoya, Nobuaki Imai, Masatoshi Itoh, Noritaka Kitamura, Shin'ichiro Michimasa, Takeshi Y Saito, Shumpei Yamazaki, Shohei Yonekura Fermion pair condensation is expected to be a universal phenomenon in the mass hierarchy of many body systems such as atoms, nuclei, and quarks. Nucleon pair condensation plays important roles in both nuclei and nucleonic matter, or neutron stars. The pair rotation is a signal of pair condensation, in which the transition to ground state is much stronger than that to excited state. The existence of the condensation of neutron-neutron (nn) pairs was confirmed in Sn isotopes, while the condensation of proton-neutron (pn) pairs in the 3S1 channel is still not discovered. A two-nucleon transfer reaction (α, 6Li) is a good candidate for an effective probe, providing clear identification of the spin-parity of the final state and a good momentum matching condition. In this research, the reaction study was performed. |
Wednesday, November 29, 2023 11:15AM - 11:30AM |
D10.00010: PANDORA Project: Study of Photonuclear Reactions below A = 60 Atsushi Tamii Photo-nuclear reactions in the mass region below a mass of 60 will be systematically investigated in the project PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics). Virtual photon exchange by proton scattering and a high-intensity real-photon beam by laser Compton scattering will be used to excite target nuclei to determine the photo-absorption cross-sections covering the giant dipole resonance. Decay particles and gammas will be measured in coincidence. The primary motivation of the project is to determine the energy loss process of the nuclei consisting the Ultra-high-energy cosmic rays (UHECRs) in the inter-galactic propagation. UHECRs are observed on earth up to above 1020 eV by observatories such as Pierre Auger and Telescope Array. The origin and the acceleration mechanism remain a mystery. A recent analysis of the air-shower depth distribution showed a trend to be larger in mass between a proton and an iron at the highest energy. UHECR nuclei are predicted to lose their energy primarily by emitting particles after photo-nuclear excitation by absorbing a cosmic microwave background (CMB) photon. Thus, photo-absorption cross-sections and decay branching ratios are the key ingredients for understanding the energy and mass evolution of UHECRs during the inter-galactic propagation. |
Wednesday, November 29, 2023 11:30AM - 11:45AM |
D10.00011: Intruder structure in 11Li from an ab initio perspective Mark A Caprio, Calvin W Johnson The ground state of 11Li has a well-known neutron halo structure, which, in a shell-model interpretation, arises from intruder contributions, in which neutrons are excited across the N=8 shell closure. Ab initio no-core configuration interaction (NCCI) calculations, for light nuclei in general, predict a low-lying spectrum which includes both normal (0ℏω) and intruder (2ℏω) states. The convergence of intruder states can be a challenge, but, in calculations with sufficiently soft interactions, the intruder states approach their low-lying physical energies. In 11Li, we find that the ground state and low-lying states are described by strong two-state mixing, between normal and intruder configurations, involving distinct Elliott SU(3) structure and radically different deformation. |
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