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 MC: Nuclear Reactions 2 |
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Chair: Takashi Nakamura, Tokyo Institute of Technology Room: Hilton Kohala 2 |
Saturday, October 27, 2018 2:00PM - 2:15PM |
MC.00001: Discovery of 60Ca Oleg B. Tarasov, DeukSoon Ahn, Daniel Bazin, Naoki Fukuda, Alexandra Gade, Marc Hausmann, Naoto Inabe, S. Ishiukawa, N. Iwasa, Keita Kawata, T. Komatsubara, Toshiyuki Kubo, Kensuke Kusaka, David Joseph Morrissey, Masao Ohtake, Hideaki Otsu, Mauricio Portillo, T. Sakakibara, Hiroyoshi Sakurai, Hiromi Sato, Bradley M Sherrill, Yohei Shimizu, Andreas Stolz, Toshiyuki Sumikama, Hiroshi Suzuki The discovery of the important neutron-rich nucleus 60Ca and seven others near the limits of nuclear stability is reported from the fragmentation of a 345 MeV/u 70Zn projectile beam on 9Be targets at the Radioactive Ion-Beam Factory of the RIKEN Nishina Center. The produced fragments were analyzed and unambiguously identified using the BigRIPS two-stage in-flight separator. The results are compared with the drip lines predicted by a variety of mass models. |
Saturday, October 27, 2018 2:15PM - 2:30PM |
MC.00002: Production of very neutron-rich Pd isotopes around N = 82 by projectile fragmentation of a RI beam of 132Sn at 280 MeV/u Hiroshi Suzuki, Koichi Yoshida, Naoki Fukuda, Hiroyuki Takeda, Yohei Shimizu, DeukSoon Ahn, Toshiyuki Sumikama, Naohito Inabe, Tetsuro Komatsubara, Hiromi Sato, Zeren Korkulu, Kensuke Kusaka, Yoshiyuki Yanagisawa, Masao Ohtake, Hideki Ueno, Shin'ichiro Michimasa, Noritaka Kitamura, Keita Kawata, Nobuaki Imai, Oleg B. Tarasov, Daniel Bazin, Toshiyuki Kubo, Jerry Nolen, Walter F Henning We have produced very neutron-rich Pd isotopes around N = 82 by projectile fragmentation of a radioactive isotope (RI) beam of 132Sn using the BigRIPS separator and the ZeroDegree spectrometer at RIKEN RI Beam Factory. A two-step reaction scheme [1], a projectile fragmentation of RI beams, has been proposed for production of mid-heavy very-neutron-rich RIs around N = 82. In this scheme, a long-lived RI (e.g. 132Sn) is produced by ISOL and post-accelerated, then more exotic nuclei (125-128Pd) are produced by fragmentation. This scheme may have an advantage for obtaining yields of such RIs compared to in-flight fission of 238U or direct production by ISOL. The in-flight fission of 238U is useful for production of mid-heavy nuclei, whereas the production cross-sections decrease drastically in such exotic region. On the other hand, much yields are obtained in target by ISOL, whereas exotic nuclei with half-lives < ~1 ms cannot be supplied because of bad extraction efficiency. To evaluate the usefulness of the two-step reaction scheme, we have measured the cross sections of the neutron-rich RIs produced from the 132Sn beam and compared their production yields by this scheme and the in-flight fission of 238U. Reference [1] K. Helariutta et al., Eur. Phys. J. A 17 (2003) 181. |
Saturday, October 27, 2018 2:30PM - 2:45PM |
MC.00003: Nucleon pickup cross sections to explore nucleon momentum distributions and nuclear structure Mitsunori Fukuda, Natsuki Tadano, Shintaro Yamaoka, Masaomi Tanaka, Junichi Ohno, Daiki Nishimura, Maya Takechi, Hang Du, Shigekazu Fukuda, Takuji Izumikawa, Yuki Kanke, Atsushi Kitagawa, Kensaku Matsuta, Mototsugu Mihara, Sadao Momota, Daiki Murooka, Takashi Ohtsubo, Hiroyuki Oikawa, Shinji Sato, Jiro Shimaya, Yuki Takeuchi, Shinji Suzuki, Takeshi Suzuki, Yutaro Tanaka, Takayuki Yamaguchi Compared to the projectile fragmentation cross sections, nucleon pickup cross sections at E/A > 100 MeV have not been so well investigated neither experimentally nor theoretically. One-nucleon pickup cross sections may have rich information on, for example, nucleon momentum distribution in nuclei or nuclear structure. Therefore we measured one-nucleon pickup cross sections of 16O beam at a few 100 MeV/nucleon. |
Saturday, October 27, 2018 2:45PM - 3:00PM |
MC.00004: ABSTRACT WITHDRAWN
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Saturday, October 27, 2018 3:00PM - 3:15PM |
MC.00005: Production of n-rich nuclei via 2-proton knockout with deuterium target Midori Miwa, Tomohiro Uesaka, Yuki Kubota, He Wang, Alexandre Obertelli, Hideaki Otsu, Pieter Doornenbal Production of neutron-rich nuclei through one-nucleon knockout (p,2p) reactions has been successfully demonstrated with the MINOS at RIBF. In future RIBF experiments, a method to remove more than one protons with a reasonable rate will be required for production of more neutron-rich nuclei. At present there is no consensus on what is the best reaction for two-proton removal. In this presentation, a performance of the (d,3pn) reaction with the MINOS as a candidate of the two-proton knockout driver in future RIBF experiments is discussed. The experiment was carried out using the SAMURAI spectrometer. A secondary cocktail beam including 58Ti was produced with projectile fragmentation reactions of a primary 70Zn beam at 345 MeV/u impinging on a beryllium target. The liquid hydrogen and deuterium with thicknesses of 1.1 g/cm2 and 1.8 g/cm2, respectively, were used as the secondary targets. The cross sections were derived by counting the numbers of particles before and after the target, considering an effective beam intensity. It was found that cross section for two-proton removal with a deuteron target is larger by a factor of ~3 than that with a proton target. This fact may imply possible advantages of a deuteron target to produce neutron-rich nuclei via two-proton knockout. |
Saturday, October 27, 2018 3:15PM - 3:30PM |
MC.00006: Neutron spectroscopic studies with the CATRiNA array Jesus F Perello, Sergio J Almaraz-Calderon, Benjamin Asher, Lagy T Baby Nuclear reactions involving neutrons play a crucial role in nuclear astrophysics research. Experimental studies of neutron-rich and neutron-deficient nuclei are becoming available with the advent of advanced radioactive beam facilities. New detection systems are in need to study nuclear reactions with these exotic nuclei. Neutron detection arrays should be able to perform neutron spectroscopy and use neutrons to 'tag' other reaction by-products. At Florida State University we have developed the Compound Array for Transfer Reactions in Nuclear Astrophysics (CATRiNA), an array of 16 deuterated-benzene (C6D6) scintillators as neutron detectors with fast-response time and excellent pulse-shape-discrimination capabilities. Moreover, C6D6 detectors provide a structured pulse-height spectrum, which has shown potential for neutron spectroscopy in addition to the traditional time-of-flight technique. CATRiNA was designed to measure (d,n) and (3He,n) reactions to perform spectroscopic studies of nuclei relevant for nuclear structure and nuclear astrophysics. In this work, we will discuss the characterization of the CATRiNA detectors and preliminary results on neutron spectroscopic studies will be presented. |
Saturday, October 27, 2018 3:30PM - 3:45PM |
MC.00007: Development of dispersion matching optics of primary beam for SRC – BigRIPS system at RIBF Shota Y Matsumoto, DeukSoon Ahn, Hiroyuki Fujioka, Naoki Fukuda, Nobuhisa Fukunishi, Geissel Hans, Naohito Inabe, Kenta Itahashi, Kensuke Kusaka, Takahiro Nishi, Yohei Shimizu, Toshiyuki Sumikama, Hiroshi Suzuki, Motonobu Takaki, Hiroyuki Takeda, Yoshiki Tanaka, Tomohiro Uesaka, Yoshiyuki Yanagisawa, Koichi Yoshida We are developing dispersion matching optics for SRC – BigRIPS system at RIBF, aiming at systematic precision spectroscopy of pionic atoms via the (d, 3He) reaction and searching for double Gamow–Teller giant resonances via the (12C, 12Be(02+)) reaction. We improve the measurement technique in the missing mass spectroscopy. Both experiments use primary beam and the same detector configuration for missing-mass spectroscopy. In these experiments, the largest contribution to the resolving power is a primary beam momentum spread. Therefore we develop a dispersion matching optical system to suppress the contribution from the momentum spread at the focal plane. We performed machine study of beam transfer line (beam line for primary beam) and BigRIPS (beam line for secondary beam) at RIBF in June 2018 in order to achieve the dispersion matching condition. In this experiment, we estimated optical matrices in the beam transfer line based on the measured data by detectors located in the BigRIPS. We report the results of the machine stydy and the future plan. |
Saturday, October 27, 2018 3:45PM - 4:00PM |
MC.00008: Kr+C Reactions to Explore the Asymmetry Dependence of the Nuclear Caloric Curve Alan McIntosh, Lauren Heilborn, Sherry J Yennello Our previous investigations have demonstrated that the nuclear caloric curve depends on the neutron-proton asymmetry. Such a dependence is impacted by the asymmetry energy, and, if sufficiently well characterized, could be used to constrain the equation of state. We have conducted a new experiment to systematically study the asymmetry dependence of the caloric curve. Collisions of 78-Kr and 86-Kr beams with 12-C targets have been performed at 15, 25, and 35 MeV/u. Light charged particles were measured in the FAUST (a Si-CsI array) from 1.6 to 45.5 degrees. Heavy residues were been measured with the QTS (a focusing spectrometer) from 0.9 to 2.3 degrees. Fusion residues are separated from the deep-inelastic residues on the basis of their velocity. The energy and composition of the beam determine the composition and excitation of the compound nuclei after fusion. The light charged particle yields and kinetic properties are sensitive to the temperature of the hot compound nuclei, allowing caloric curves to be constructed. |
Saturday, October 27, 2018 4:00PM - 4:15PM |
MC.00009: Projectile-like fragment production studies using coincident neutrons Sharon Stephenson, the MoNA Collaboration The production of nuclei near the neutron dripline at Radioactive Ion Beam (RIB) facilities requires multi-step reactions between primary beams and targets. Understanding these multi-step reactions narrows constraints on secondary beam production rates and therefore optimizes beam time. Experimental planning typically depends on empirical parameterizations like EPAX, but results can differ from experiment [1]. At the National Superconducting Cyclotron Laboratory (NSCL), the MoNA Collaboration measured coincident neutrons and charged fragments in the 32Mg + 9Be reaction in order to study the formation of the precursor states, i.e. projectile-like fragments (PLF’s). Charged fragments were deflected by the Sweeper magnet into a suite of charged particle and coincidence neutrons measured in the Modular Neutron Array (MoNA). The rigidity of the Sweeper was varied during this experiment allowing the detection of a range of isotopes. Analysis of the neutron multiplicity and energy distributions in coincidence with sodium, neon, or fluorine charged fragments will be presented. [1] M. Mocko, et al., Physical Review C 74 054612 (2006) |
Saturday, October 27, 2018 4:15PM - 4:30PM |
MC.00010: Proton-proton correlation functions measured near the Fermi Energy using the FAUST Lauren Heilborn, Alan McIntosh, Sherry J Yennello Proton-proton correlation functions have been predicted to be sensitive to the form of the nuclear equation of state. Previous experiments have searched for evidence of this sensitivity and shown the importance of event selection in correlation function extraction. We have performed a new experiment varying the neutron-proton asymmetry of the system by varying the composition at constant atomic number and by varying the composition at constant mass in collisions around Atot=98 just above the Fermi energy. The FAUST (a Si-CsI array) was used to measure protons (and other light charged particles) produced from 1.6 to 45 degrees. FAUST was upgraded with position sensitive silicon detectors which have <200um resolution within the detector. Proton proton correlation functions have been extracted from the experimental data. These can be compared with correlation functions from a transport model, Boltzmann-Uehling-Uhlenbeck. |
Saturday, October 27, 2018 4:30PM - 4:45PM |
MC.00011: Experimental constraint on an exotic spin- and velocity-dependent interaction with a spin-exchange relaxation-free magnetometer Young Jin Kim, Pinghan Chu, Igor Savukov Many theoretical extensions of the Standard Model of particle physics suggested the existence of new hypothetical fundamental bosons to resolve the strong charge-parity (CP) problem in the quantum chromodynamics, such as the axion and axionlike particles. The exotic particles are very light and can mediate new macroscopic interactions between fermions with an interaction range from micrometers to centimeters. To explore exotic interactions, we recently proposed a novel experimental approach based on a spin-exchange relaxation-free (SERF) magnetometer, the most sensitive cryogen-free magnetic-field sensor reaching femto-Tesla sensitivity. This approach aims to sensitively detect magnetic-field-like effects from the exotic interactions between SERF polarized electrons and particles of an external solid-state mass. With our experimental approach, we conducted a search for an exotic spin- and velocity-dependent interaction between SERF polarized electrons and unpolarized nucleons. In this talk, we will report experimental results on the interaction with 82 hours of data averaging. |
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