Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session MM: Nuclear Structure A=30-60 |
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Chair: Adam Fritsch, Gonzaga University Room: Hilton Queen's 6 |
Saturday, October 27, 2018 2:00PM - 2:15PM |
MM.00001: Shell-model Interpretation of the Intruder States in 38Cl Rebeka Sultana Lubna, Konstantinos Kravvaris, Samuel L Tabor, Vandana Tripathi, Alexander Volya, Elizabeth Rubino, Maria Anastasiou, Benjamin Asher, Lagy T Baby, Jonathan Baron, David Dwaine Caussyn, David Clarke, Jesus Perello, Nabin Rijal, Kalisa Villafana, James Allmond
The excited states in 38Cl were populated by the 26Mg(18O, αpnγ)38Cl fusion evaporation reaction at Elab=50 MeV in John. D. Fox laboratory, Florida State University. The experimental observations have been interpreted by shell model calculations using FSU-A interaction, currently being developed by our group [1]. In this interaction, we have chosen the approach of fitting experimental data started from an existing interaction. The single particle energies of the fp shell orbitals along with the monopole terms from the sd-pf cross shell two body matrix elements were adjusted to fit the experimental data compiled from the nuclei ranging from 23Ne to 40K. The interaction well explains 0hbarΩ and 1hbarΩ states in 38Cl. FSU-A also predicts 0p-0h and 1p-1h states of the nearby isotopes which will also be discussed along with future plans to refine this interaction to make it more universal. [1] R. S. Lubna, K. Kravvaris, A. Volya, S.L. Tabor, V. Tripathi |
(Author Not Attending)
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MM.00002: Exploring High-Spin States in $^{39}$Ar using a Fusion-Evaporation Reaction Brittany Abromeit, Samuel L Tabor, Vandana Tripathi, Rebeka Sultana Lubna, Konstantinos Kravvaris, Elizabeth Rubino, Alexander Volya In nuclear physics, a goal is to understand the structure of nuclei and use theory to predict their properties: experimental data can help put constraints on the theories used to model these nuclei. At FSU, a fusion-evaporation reaction was conducted, allowing for the creation of high-spin states in $^{39}$Ar. The 7 day experiment used a $^{14}$C beam impinging on a $^{27}$Al target. To observe the high-spin states in $^{39}$Ar, the FSU gamma array, consisting of 10 High-Purity Germanium (HPGe) detectors, was coupled with a particle telescope. The selection of the proton-neutron decay channel allowed for all gamma decays occurring in coincidence with the emission of protons and neutrons to be observed. Using the coincidences, matrices were constructed to further study the particle-gamma-gamma and gamma-gamma coincidences. The study of these matrices lead to the discovery of new energy levels in $^{39}$Ar suspected of having high spin, due to the nature of the reaction and direct feeding into previously known high-spin states. The new potentially high-spin states have been compared to a shell model interaction that is being developed at FSU. Results will be discussed. |
Saturday, October 27, 2018 2:30PM - 2:45PM |
MM.00003: Cross-Shell Excitations and High Spins in 41K and 41Ca Elizabeth Rubino, Samuel L. Tabor, Vandana Tripathi, Maria Anastasiou, Benjamin Asher, Lagy T Baby, Jonathan Baron, David Dwaine Caussyn, David Clarke, Jesus Perello, Konstantinos Kravvaris, Nabin Rijal, Kalisa A Villafana, Alexander S Volya, James M Allmond The work to be presented here investigates the nuclear structure of |
Saturday, October 27, 2018 2:45PM - 3:00PM |
MM.00004: Electroweak transitions in intermediate mass nuclei Grigor H Sargsyan, Kristina D Launey, Tomas Dytrych, Jerry P Draayer We calculate beta decays and B(E2) values using the ab initio symmetry-adapted no-core shell model (SA-NCSM). The SA-NCSM employs emergent symmetries in nuclei in order to decrease the dimensionality of the model space, this allows us to reproduce the low-energy nuclear dynamics using only a small fraction of the model space, thus expanding the reach of ab initio theory to heavier nuclei, such as sd-shell nuclei and 48Ca. This work aims to contribute to the study of the long standing gA quenching problem and ultimately to study 48Ca and 48Ti, of interest to neutrinoless double beta decays. |
Saturday, October 27, 2018 3:00PM - 3:15PM |
MM.00005: Direct determination of the neutron skin thickness of 48Ca probed via proton elastic scattering and the ESPRI project Juzo Zenihiro Equation of state (EOS) of the nuclear matter controls the properties of not only the finite quantum system, nuclei, but also the structure of neutron stars and the dynamics of supernovas. Presently, the isospin-asymmetric term of the EOS, the symmetry energy is much less certain. The density dependent term of the symmetry energy plays very important role to form the neutron-rich matter. Therefore, it is very essential for understanding the neutron star. The neutron skin thickness (Δrnp) is the most important parameter to understand the density dependence of the symmetry energy. It is very difficult, however, to determine Δrnp accurately due to the theoretical model ambiguities. Proton elastic scattering is one of the best probes to extract the direct information of proton and neutron distributions. We have successfully determined the model independent neutron distributions and the Δrnp of Sn and Pb isotopes. We will report a result of Δrnp in 48Ca. Recently Δrnp in 48Ca has received much attention because the ab initio calculation including a multi-nucleon force can be applied to Ca region. This helps us to directly understand the role of the multi-nucleon force which is essential for the EOS at high density. |
Saturday, October 27, 2018 3:15PM - 3:30PM |
MM.00006: Direct mass measurements of very neutron-rich calcium isotopes beyond N=34 Shin'ichiro Michimasa, Motoki Kobayashi, Yu Kiyokawa, Shinsuke Ota, D. S. Ahn, H. Baba, G. P. A. Berg, M. Dozono, N. Fukuda, E. Ideguchi, S. Kawase, T. Kubo, Y. Kubota, C. S. Lee, D. Nishimura, H. Sakai, Y. Shimizu, A. Stolz, H. Suzuki, M. Takaki, H. Takeda, S. Takeuchi, T. Uesaka, R. Yokoyama, S. Shimoura Nuclear mass is one of the fundamental quantities expressing its nuclear structure property, and systematic investigation of nuclear masses can illuminate unexpected phenomena such as emergency of new magic numbers and disappearance of conventional magic numbers. In order to obtain the conclusive evidence of the emergency of theoretically-proposed magic number N=34, we have performed an experiment to measure the atomic masses of very neutron-rich calcium isotopes beyond N=34 and have determined the atomic masses of 55-57Ca isotopes successfully for the first time. The experiment was done using the BigRIPS-SHARAQ system at RIKEN RIBF. The masses were determined by TOF-Bρ method in use of CVD diamond timing detectors, LP-MWDC tracking detectors and a PPAC detector. The determined masses made clear a magic nature of neutrons in 54Ca and the emergence of the new magic number 34 became evident in neutron-rich calcium isotopes. In this contribution, we will present details of the experiment and discuss the obtained results. |
Saturday, October 27, 2018 3:30PM - 3:45PM |
MM.00007: Coulomb excitation of 52Ca Yusuke Fujino, Yasuhiro Togano, Kazuo Ieki The Coulomb excitation of 52Ca at 240 MeV/nucleon has been measured. In neutron-rich nuclei, it is known that the magic numbers evolve with a neutron-proton ratio (i.e. disappearance at N =8,20)[1]. For Calcium isotopes, 52Ca is supposed to be the doubly magic nucleus with Z=20 and N =32, possible new magic number, based on the relatively high 2+1 energy. And the reduced transition probability B(E2;0+1→2+1 ) has not yet been measured. To disclose the nuclear collectivity, we have measured the B(E2) value of 52Ca with Coulomb excitation. The experiment was performed by using SAMURAI spectrometer at RIKEN RIBF. The beam at 240 MeV/nucleon impinged on a lead and carbon target, and the reaction residue was identified by using the SAMURAI spectrometer. The de-excitation γ-ray from 52Ca was detected by using the CsI(Na) array CATANA and LaBr3 detectors. In the present talk, the Coulomb excitation cross section to the first 2+ state of 52Ca will be reported. [1] O.Sorlin and M.-G.Porquet, Prog. Part. Nucl. Phys. 61,602 (2008) |
Saturday, October 27, 2018 3:45PM - 4:00PM |
MM.00008: Production of isomers around 52Fe nucleus via projectile fragmentation Keita Kawata, Shinsuke Ota, Masanori Dozono, Shin'ichiro Michimasa, Hiroki Nishibata, Chihiro Iwamoto, Noritaka Kitamura, Shoichiro Masuoka, Rieko Tsunoda, Tomoya Harada, Hideyuki Sakai, Nobuaki Imai, Kentaro Yako, Tomoya Sato Nucleosynthesis heavier than iron in the supernova explosion is one of the attractive topics. Electron capture rates of nuclei near iron are inputs for network calculation. The electron capture rate above beta-decay threshold can be estimated from the strength distribution of the charge exchange reactions.Nuclei in high temperature circumstances may be in excited state, and then the information of charge exchange reaction from excited state is desired. Experiments were performed at HIMAC. The isomer ratio around 52Fe are measured by using projectile fragmentation from 58Ni(0+),59Co(7/2-) and 82Kr(0+) at 350MeV/u with changing longitudinal momentum transfer, transverse momentum transfer and incident nucleus. To obtain the transverse momentum dependence the incident beam angle to the target was changed. The typical isomer ratio of 52Fe is larger than 5 %. The results on the isomer ratio around Fe will be presented. |
Saturday, October 27, 2018 4:00PM - 4:15PM |
MM.00009: In-beam γ spectroscopy of 55Ca and 55K via nucleon knockout reactions Takuma Koiwai, Kathrin Wimmer, Pieter Doornenbal, Alexandre Obertelli The shell model is very successful in describing the properties of stable nuclei. However, modifications of the nuclear shell structure have been observed especially for the nuclei far from stability. For very exotic Ca isotopes, new magic numbers at N = 32, 34 have been inferred from gamma-ray spectroscopy and mass measurements. However, more direct indications for shell closures can be obtained from the single-particle structure of neighboring nuclei. In this study we have investigated the proton and neutron single particle structure of 56Ca using knockout reaction combined with in-beam gamma-ray spectroscopy. The experiment was performed at RI Beam Factory, Japan. A primary 70Zn beam with 345 MeV/u impinged on 10 mm-thick 9Be production target. Secondary beams including 56Ca were separated and identified by BigRIPS and impinged on the liquid hydrogen target MINOS. The detector array DALI2 was placed around MINOS to measure the gamma-rays emitted from the reaction products. Fragments were identified by the large-acceptance multi-particle spectrometer SAMURAI. In this talk we will present the preliminary results and comparison to theoretical calculations. In-beam γ spectroscopy of 55Ca and 55K via nucleon knockout reactions. |
Saturday, October 27, 2018 4:15PM - 4:30PM |
MM.00010: Investigation of decay properties of neutron-rich isotopes in the vicinity of 60Ca Andreas Stolz, DeukSoon Ahn, Thomas Baumann, Daniel Bazin, Jill S. Berrryman, Georg Bollen, Marco Cortesi, Alex C. Dombos, Alexandra Gade, Thomas N. Ginter, Caley Harris, Marc Hausmann, Toshiyuki Kubo, Elaine Kwan, Sean N. Liddick, Stephanie Lyons, David J. Morrissey, Naoki Fukuda, Alicia Palmisano, Jorge Pereira, Mauricio Portillo, Yohei Shimizu, Mallory Smith, Artemis Spyrou, Mathias Steiner Neutron-rich isotopes in the close vicinity of 60Ca from the fragmentation of a 140 MeV/u 82Se beam on a 9Be target were separated and identified in the A1900 Fragment Separator at the National Superconducting Cyclotron Laboratory at Michigan State University. A large-momentum acceptance beam optics of the separator with a new momentum-compression wedge degrader at the first optical focus was used to increase the transmission efficiencies. Fragments were identified event-by-event by measurement of energy loss and time-of-flight and subsequently implanted in a double-sided silicon strip detector surrounded by two HPGe detectors to measure decay properties. Preliminary results will be reported. |
Saturday, October 27, 2018 4:30PM - 4:45PM |
MM.00011: Geant4 Simulations of Nuclear Isomer Gamma Emission Detection Adam L Fritsch, James Aaron Brown, Andrew Clusserath, Bryce Makela When an atomic nucleus is excited, it can form a nuclear isomer, a metastable state with a relatively long half-life. By experimentally investigating the energy levels of neutron-rich isomers, nuclear structure models can be better constrained. Using Geant4, Monte Carlo simulations have been performed to determine optimal detector geometry and placement near a target for measurement of nuclear isomer de-excitation via gamma emission. Various beam and target combinations have been simulated. Preliminary results will be presented. |
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