Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session FF: Mini-Symposium on Transfer and Charge Exchange Reaction Studies with Stable and Radioactive Ion Beams II |
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Chair: Sharon Stephenson, Gettysburg College Room: King's 2 |
Friday, October 10, 2014 9:00AM - 9:30AM |
FF.00001: Charge Exchange Reaction: a powerful tool to study the ``Weak Response'' of nuclei Invited Speaker: Yoshitaka Fujita Weak-interaction processes, for example, Gamow-Teller (GT) transitions, play important roles in the stellar evolution and nucleosynthesis. $\beta$-decay studies provide the most direct information on the transition strengths caused by these processes, but the accessible $E_x$ range is limited by the decay $Q$ values. On the other hand, Charge-Exchange (CE) reactions can access the transitions to higher excited states. Pioneering ($p,n$) reactions at intermediate incident energies ($E_{\rm beam} > 100$ MeV/nucleon) found the main part of the GT transition strength expected by the GT sum rule in GT resonances (GTRs) situated in the $E_x = 10-15$ MeV region, and detailed studies in combination with ($n,p$) studies provide further knowledge on the GT sum rule. Recent development of CE reactions toward higher resolution and sensitivity is impressive. The ($p,n$)-type ($^3$He,$t$) reaction achieved a $\Delta E \sim 30$ keV and GTRs were resolved into individual states. The ($d,^2$He) reaction also provides much better resolution in the ($n,p$)-type study and recent ($t,^3$He) reaction in coincidence with $\gamma$ decay could detect weakly excited states. We can also see future in the CE reactions using unstable incident beams. [Preview Abstract] |
Friday, October 10, 2014 9:30AM - 9:45AM |
FF.00002: (p,n) Charge-Exchange Reactions in Inverse Kinematics Samuel Lipschutz Charge-exchange experiments at intermediate energy yield important information about collective excitations with spin-isospin degrees of freedom. The properties of isovector giant resonances in neutron-rich rare-isotopes provide stringent tests of theoretical models and are important inputs for modeling of astrophysical phenomena. The (p,n) charge-exchange reaction in inverse kinematics has been developed as a new tool for investigating isovector giant resonances in rare isotopes. The technique, which involves the detection of low-energy neutrons that recoil from a hydrogen target, while detecting fast beam-like ejectiles in a magnetic spectrometer, was successfully employed at NSCL to study the $^{56}$Ni(p,n) reaction. Continuing with this technique a $^{16}$C(p,n) experiment at 100 MeV/u aimed at extracting isovector multipole strengths up to excitation energies of 30 MeV was preformed. The Low Energy Neutron Detector Array (LENDA) and the Versatile Array of Neutron Detectors at Low Energy (VANDLE) were utilized in combination with the Ursinus Liquid Hydrogen Target and the S800 spectrometer to perform this experiment. Preliminary results will be shown. [Preview Abstract] |
Friday, October 10, 2014 9:45AM - 10:00AM |
FF.00003: The parity-transfer reaction $(^{16}{\rm O},^{16}{\rm F})$ for studies of pionic $0^-$ mode Masanori Dozono The spin-dipole (SD) $0^-$ excitation is an important topic in the study of spin-isospin responses in nuclei. Because the $0^-$ excitation carries the same quantum number as a pion, its strength distribution is expected to reflect pion-like correlations in nuclei such as tensor correlations. Despite this importance, experimental information on $0^{-}$ states is very limited because of a lack of experimental tools that are suitable for $0^{-}$ studies. we propose a new probe, a parity-transfer $({}^{16}{\rm O},{}^{16}{\rm F}(0^-))$ reaction for $0^-$ studies. The parity-transfer reaction uses $0^+ \rightarrow 0^{-}$ transition in the projectile to probe $0^-$ states in a target nucleus. This reaction has unique sensitivity to unnatural parity states, which is an advantage over other reactions used so far. For the first parity-transfer measurement, we performed a ${}^{12}{\rm C}({}^{16}{\rm O},{}^{16}{\rm F}(0^-)){}^{12}{\rm B}$ experiment at the RIKEN RIBF facility by using a SHARAQ spectrometer. In this presentation, we will report the details of the experiment and the results. [Preview Abstract] |
Friday, October 10, 2014 10:00AM - 10:15AM |
FF.00004: Missing mass spectroscopy of $^{4}$H via exothermic charge exchange reaction ($^{8}$He, $^{8}$Li$\gamma$) Hiroyuki Miya Charge exchange reactions are powerful tools in the study of spin-isospin responses in nuclei. The RI beam induced reactions have the variety of spin-isospin and the high $Q$-Value with internal energy. We aimed to study the nuclear structure of unbound nuetron rich 4H. This work is the first measurement of ($^{8}$He(0$^{+}$), $^{8}$Li(1$^{+}$)) reaction at the energy of 190 MeV/u. This reaction has the feature of the large mass difference of 11 MeV and tagging $\Delta$ $S$ = $\Delta$ $T$ = 1 transition mode by detecting de-excited $\gamma$-rays (980~keV) form first 1$^{+}$ state in $^{8}$Li. The experiment was performed with the SHARAQ spectrometer combined with the $\gamma$-ray detector array DALI2 in RIBF. The $^{8}$He beam produced via thr projectile fragmentation of $^{18}$O was irradiated liquid $^{4}$He target at the intensity of about 2 MHz. Excitation energy was obtained by measuring the momenta of the $^{8}$He and $^{8}$Li beams in the beamline and the SHARAQ by using missing-mass method. In this presentation, the result of the present experiment will be reported. [Preview Abstract] |
Friday, October 10, 2014 10:15AM - 10:30AM |
FF.00005: Neutrino nuclear responses for double beta decays and astro neutrinos by charge exchange reactions Hiroyasu Ejiri Neutrino nuclear responses are crucial for neutrino studies in nuclei. Charge exchange reactions (CER) are shown to be used to study charged current neutrino nuclear responses associated with double beta decays(DBD)and astro neutrino interactions [1,2]. CERs to be used are high energy-resolution (He3,t) reactions at RCNP, photonuclear reactions via IAR at NewSUBARU [3] and muon capture reactions at MUSIC RCNP and MLF J-PARC. The Gamow Teller (GT) strengths studied by CERs reproduce the observed 2 neutrino DBD matrix elements [2]. The GT and spin dipole (SD) matrix elements are found to be reduced much due to the nucleon spin isospin correlations and the non-nucleonic (delta isobar) nuclear medium effects. Impacts of the reductions on the DBD matrix elements and astro neutrino interactions are discussed.\\[4pt] [1] H.Ejiri, JSPS 74 (2005) 2101.\\[0pt] [2] J. Vergados, H. Ejiri, F. Simkovic, Rep. Prog. Phys. 75 (2012) 106301.\\[0pt] [3] H. Ejiri et al., Phys. Rev. C 88 (2013) 054610.\\[0pt] [4] H. Ejiri, N. Soukouti, J. Suhonen, Phys. Lett. B 729 (2014) 27. [Preview Abstract] |
Friday, October 10, 2014 10:30AM - 10:45AM |
FF.00006: Measurement of $\gamma$-rays from giant resonances of $^{12}C$ and $^{16}O$ Iwa Ou Oxygen and carbon are the most common targets in neutrino experiments such as Super Kamiokande(H$_2$O) and Daya-Bay (liquid scintillator). The $\gamma$-ray production from neutral current (NC) $\nu-^{16}$O and $\nu-^{12}$C (inelastic scattering) is applicable to the measurement of core-collapse supernova neutrinos. A core-collapse supernova emits all type of neutrino with mean energy of 10-20MeV. In most neutrino detectors, the main signal is charged current event which can detect electron type neutrino only. While in NC event, mu and tau type neutrino can be detected. Therefore NC event is very important for the understanding of supernova mechanism. NC events will be identified by detecting the $\gamma$-rays emitted from giant resonances of $^{16}$O and $^{12}$C. But there is no experimental data for $\gamma$-ray production from these resonances. Our goal is to measure the $\gamma$-ray emission probability and energy spectrum from these resonances. We carried out an experiment to measure $\gamma$-rays from giant resonance of $^{16}$O and $^{12}$C using 400MeV proton beam, magnetic spectrometer ``Grand Raiden'' and NaI(Tl) $\gamma$-detecter at Research Center for Nuclear Physics in Osaka University. In this talk, experimental setup and current analysis status will be presented. [Preview Abstract] |
Friday, October 10, 2014 10:45AM - 11:00AM |
FF.00007: (6Li,d) reactions at sub-Coulomb energies for nuclear astrophysics Griogry Rogachev, Melina Avila, Evgeniy Koshchiy, Lagy Baby, Joseph Belarge, Kirby Kemper, Anthony Kuchera, Daniel Santiago-Gonzalez, Akram Mukhamedzhanov Near $\alpha$-threshold states play an important role in nuclear astrophysics as they often determine the ($\alpha$,$\gamma$), ($\alpha$,p) and ($\alpha$,n) reaction rates. Clustering can enhance the corresponding cross sections and it is necessary to measure the partial $\alpha$-width to evaluation the low energy cross section. We will discuss application of sub-Coulomb ($^6$Li,d) and ($^7$Li,t) $\alpha$-transfer reactions to extract an asymptotic normalization coefficients (ANCs) for the astrophysically important resonances and present new data on $^{12,13}$C,$^{16}$O($^6$Li,d) reactions. [Preview Abstract] |
Friday, October 10, 2014 11:00AM - 11:15AM |
FF.00008: Measuring $^{19}$F($\alpha $,n) with VANDLE for Nuclear Safeguards William Peters, R.C.C. Clement, M.S. Smith, S.D. Pain, S. Thompson, J.A. Cizewski, C. Reingold, B. Manning, S. Burcher, D.W. Bardayan, W.-P. Tan, E. Stech, M.K. Smith, K. Smith, R. Avetisyan, A. Long, A. Battaglia, S. Marley, A. Gyurjinyan, S. Ilyushkin, P.D. O'Malley, M. Madurga, S.V. Paulauskas, S. Taylor, M. Febbraro UF$_{6}$ is used in many parts of the Uranium Fuel Cycle, and various techniques are used by nonproliferation agencies to monitor and account for the material. One of the most promising non-destructive assay (NDA) methods consists of measuring gross neutron rates induced by uranium-decay alpha particles reacting with the fluorine and emitting a neutron. This method, however, currently lacks reliable nuclear data on the $^{19}$F($\alpha $,n) reaction cross section to determine an accurate neutron yield rate for a given sample of UF$_{6}$. We have used the Versatile Array of Neutron Detectors at Low Energy (VANDLE) to measure the cross section and coincident neutron spectrum over an energy range pertinent to NDA in a two part experiment: First at Notre Dame with a LaF$_{3}$ target and a pulsed alpha-particle beam, and second at ORNL with a windowless He-gas target and a $^{19}$F beam. The motivation for this measurement and preliminary results will be presented. [Preview Abstract] |
Friday, October 10, 2014 11:15AM - 11:30AM |
FF.00009: An Exploratory Study of $^{38}$Ca($\alpha$,p) Resonance States in $^{42}$Ti using the $^{46}$Ti($^{4}$He,$^{8}$He)$^{42}$Ti Reaction Alexander Long, Georg Berg, Joachim Goerres, Darshana Patel, Rashi Talwar, Michael Wiescher, Manoel Couder, Kichiji Hatanaka, Hiro Fujita, Yoshitaka Fujita, Atsushi Tamii, Kenjiro Miki, Takeshi Ito, Bin Liu, John Greene During type 1 X-ray bursts, if temperatures becomes sufficiently high, ($\alpha$,p) reactions ($\alpha$p-process) can effectively bypass the slower $\beta ^{+}$ decay waiting points of the rp-process in the lower mass region A $\leq$ 40. The reaction flow of the $\alpha$p-process can reach all the way up to Sc where very little information is known about the resonance states above the $\alpha$-threshold in these proton rich nuclei. This endpoint of the $\alpha$p-process comes from an ever increasing coulomb barrier and a possible suppression of alpha strengths in the compound nuclei of the ($\alpha$,p) reactions. In order to investigate the end point of the $\alpha$p-process, the $^{38}$Ca($\alpha$,p)$^{41}$Sc reaction was indirectly studied by measuring resonance states in the compound nucleus, $^{42}$Ti, using the $^{46}$Ti($^{4}$He,$^{8}$He)$^{42}$Ti reaction with the Grand Raiden spectrometer at RCNP. The procedures of this experiment along with results will be presented. [Preview Abstract] |
Friday, October 10, 2014 11:30AM - 11:45AM |
FF.00010: Two-neutron transfer reaction mechanisms in $^{12}$C($^6$He,$^{4}$He)$^{14}$C using a realistic three-body $^{6}$He model F. Sarazin, D. Smalley, F.M. Nunes, B.A. Brown The reaction mechanisms of the two-neutron transfer reaction $^{12}$C($^6$He,$^4$He) have been studied at E$_{\mathrm{lab}}=30$ MeV at the TRIUMF ISAC-II facility using the Silicon Highly-segmented Array for Reactions and Coulex (SHARC) inside the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). In the past, the two-neutron transfer ($^{6}$He,$^{4}$He) angular distributions were often analyzed as a one-step process using a simple di-neutron plus core configuration for the $^{6}$He nucleus. In this work, the transfer angular distribution to the 2$^+_2$ 8.32 MeV state in $^{14}$C is studied using a realistic 3-body $^6$He model and advanced shell model calculations for the carbon structure, allowing to calculate the relative contributions of the simultaneous and sequential two-neutron transfer. The reaction model provides a good description of the data set and shows that while the simultaneous process is the dominant transfer mechanism, the sequential transfer contribution cannot be neglected. [Preview Abstract] |
Friday, October 10, 2014 11:45AM - 12:00PM |
FF.00011: A direct measurement of the $^6$Li(n,t)$^4$He cross section at sub-thermal neutron energy A. Yue, M. Dewey, D. Gilliam, J. Nico, G. Greene, A. Laptev The thermal neutron capture cross section for the $^6$Li(n,t)$^4$He reaction is an important neutron cross section standard. Yet few measurements of it have been performed and the ENDF/B-VII recommended value of $(938.5 \pm 1.3)$ b is based heavily on measurements performed at higher energies. The first absolute, direct measurement of the $^6$Li(n,t)$^4$He cross section at sub-thermal neutron energy has been performed at the NIST Center for Neutron Research. An alpha-gamma counter was used to measure the absolute neutron fluence of a monoenergetic neutron beam to sub-0.1\,\% precision. The alpha-gamma counter used a thick, totally absorbing target of $^{10}$B-enriched boron carbide. The rate of absorbed neutrons was determined by counting the 478 keV $^{10}$B(n,$\gamma$)$^7$Li gamma rays with calibrated high-purity germanium detectors. Simultaneously, the absolute rate of neutron-induced charged particles was measured for three thin $^6$Li targets of known density with a defined solid-angle counter. Using the known density of the $^6$Li targets and measurements of the rate of charged particles from the $^6$Li targets, the fluence of the neutron beam, and the energy of the neutron beam, we determine the $^6$Li(n,t)$^4$He cross section at $E_n=3.3$ meV to 0.3\,\% uncertainty. [Preview Abstract] |
Friday, October 10, 2014 12:00PM - 12:15PM |
FF.00012: Spin-isospin response of neutron-rich nucleus $^{8}$He via (p,n) reaction in inverse kinematics Motoki Kobayashi, Kentaro Yako, Susumu Shimoura, Shoichiro Kawase, Keiichi Kisamori, Yuki Kubota, CheongSoo Lee, Shin'ichiro Michimasa, Hiroyuki Miya, Shinsuke Ota, Motonobu Takaki, Masanori Dozono, Hideyuki Sakai, Masaki Sasano We measured the Gamow-Teller (GT) strength of the neutron-rich nucleus $^{8}$He, which has the largest neutron-to-proton ratio among all known particle-stable nuclei, to study the spin-isospin response of very neutron-rich nuclei. We performed the first measurement of the $^{8}$He$(p,n)$$^{8}$Li reaction at 190$A$ MeV in inverse kinematics at the RIKEN RI Beam Factory. Recoil neutrons with low kinetic energies were detected by the neutron detector array WINDS, which was recently developed. The residual particle $^{8}$Li and its decay product $^{7}$Li were detected by auxiliary beam line detectors, a plastic scintillator and a multi-wire drift chamber. We obtained the double differential cross sections at excitation energies up to $E_x$ $\sim$ 20 MeV, where two peaks were observed at $\sim$ 1 MeV and $\sim$ 8 MeV. We evaluated the GT strength for the neutron decay channel of the observed 8-MeV state. The result suggests that most of the GT strength is concentrated in the resonance state at $\sim$ 8 MeV. It was the first direct observation of the GT Resonance of $^{8}$He. [Preview Abstract] |
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