Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session PD: Nuclear Structure VI |
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Chair: Wanpeng Tan, University of Notre Dame Room: Grand Ballroom IV |
Saturday, October 26, 2013 10:30AM - 10:42AM |
PD.00001: ABSTRACT WITHDRAWN |
Saturday, October 26, 2013 10:42AM - 10:54AM |
PD.00002: No Core Shell Model systematics of the Fermi beta-decay matrix element Michael Kruse, Erich Ormand We study the systematics of the Fermi beta-decay matrix element by using the No Core Shell Model (NCSM). We employ the chiral N3LO NN interaction and calculate the A$=$6 triplet T$=$1 states for He-6, Li-6 and Be-6. Although the Fermi transition is energetically forbidden for A$=$6, it does provide us with a good testing ground of extrapolation techniques which we intend to employ for the A$=$10 system. The B-10 to C-10 transition has been measured experimentally and has also been calculated with various theoretical methods including the NCSM. The T$=$1 Coulomb-displacement energies lie on a parabolic curve as given by the isobaric mass multiplet equation. We calculate the b-coefficients and notice a strong correlation with the charge radius of the nuclei. The isospin mixing correction for the Fermi transition is typically linearly proportional to the size of the basis (Nmax) and thus cannot be easily extrapolated. We will present a technique in which we extrapolate the b-coefficients as well as the radius to a ``converged'' result, which we in turn use to estimate the corresponding isospin mixing correction. We will also present results on the giant isovector monopole transition. [Preview Abstract] |
Saturday, October 26, 2013 10:54AM - 11:06AM |
PD.00003: Coulomb displacement energies and isospin-nonconservation for fp-shell nuclei William Ormand, Michael Kruse, Alex Borwn, Morten Hjorth-Jensen A new isospin nonconserving (INC) interaction for fp-shell nuclei is determined empirically by fitting to experimental Coulomb displacement energies. This interaction is based on the Coulomb interaction as well as charge-asymmetric and charge-dependent components in the nucleon-nucleon sector as found in realistic nucleon interactions such as CD-Bonn and effective field theory at N3LO. The INC components arising from the nucleon-nucleon interaction were determined through a renormalization procedure from a G-matrix calculation as well as many-body perturbation theory. The overall strength of these components is tuned to reproduce experimental b- and c-coefficients of the isosbaric mass multiplet equation. A new feture of this interaction is that where possible calculations were performed using the full fp-shell; made possible with recent advances in shell-model codes and high-performance computing. With this interaction, isospin-mixing effects in the fp-shell are estimated including a new calculation of isospin-mixing corrections for Fermi transitions in the fp-shell. [Preview Abstract] |
Saturday, October 26, 2013 11:06AM - 11:18AM |
PD.00004: 4n contributions in populating unbound $^{10}$He from $^{14}$Be Michael Jones, Zach Kohley, Jesse Snyder, Thomas Baumann, Jenna Smith, Artemis Spyrou, Michael Thoennessen The ground state resonance of $^{10}$He was recently measured from the decay energy of the 3-body system $^{8}$He+n+n, and found to be at E=1.6(25) MeV with $\Gamma$ = 1.8(4) MeV. The possibility of contributions from the emission of 4 neutrons has been considered, and higher order 4 and 5-body decay energy spectra were examined. Results show that it is necessary to account for 4n emission in the 2p2n removal reaction $^{14}$Be(-2p2n)$^{10}$He. Detailed Monte Carlo simulations were performed to simulate the emission of 2 non-resonant neutrons followed by the 2n decay of $^{10}$He. Using GEANT4 and MENATE\_R, the efficiency, resolution and acceptances of MoNA (Modular Neutron Array) were incorporated into the simulations. The inclusion of 4n emission allows the simultaneous fitting of the 2 and 3-body decay spectra while reproducing the experimentally observed 4 and 5-body spectra in addition to reproducing the observed multiplicity distribution. [Preview Abstract] |
Saturday, October 26, 2013 11:18AM - 11:30AM |
PD.00005: Study of Neutron Deficient 13O Joseph Belarge, G.V. Rogachev, J. Blackmon, I. Wiedenhover, L. Baby, E.D. Johnson, A.N. Kuchera, E. Koshchiy, J. Lai, L. Linhardt, K. Macon, M. Matos, D. Santiago-Gonzalez Development of theoretical framework that allows the combination of nuclear structure calculations with the continuum is an important objective of modern nuclear theory [A. Volya, PRC 79, 044308 (2009), S. Quaglioni and P. Navratil, PRL 101092501 (2008)]. Due to the low binding energy of exotic isotopes even the lowest excited states are unbound and therefore it is essential to take the continuum into account. We studied the structure of the lightest bound oxygen isotope, $^{13}$O, through $^{12}$N+p resonance scattering using the new active target detector ANASEN [M. Matos, et al, Proc. Intern. Symp. on Nuclei in the Cosmos, July 19-23, Heidelberg, Germany, p.226 (2010)]. The experiment was performed at the John D. Fox Superconducting Accelerator Laboratory at Florida State University. A rare isotope beam of $^{12}$N ions was produced using the radioactive nuclear beam facility RESOLUT. Methane gas was used as a target and also as an active medium for the gas proportional counters of the ANASEN detector. The analysis of the p+$^{12}$N excitation functions was performed using the R-Matrix approach. The preliminary results of the experiment will be presented. [Preview Abstract] |
Saturday, October 26, 2013 11:30AM - 11:42AM |
PD.00006: Feasibility of using $^{6}$Li as a probe in studying the iso-scalar giant monopole resonance (ISGMR) in unstable nuclei using inverse kinematics J.T. Matta, U. Garg, D. Patel, G.P.A. Berg, M. Couder, S. O'Brien, K. Sault, M. Itoh, F. Takahashi, H.P. Yoshida, M. Yosoi, H. Akimune, M. Uchida, K. Kawase, T. Kawabata, X.F. Chen, D.T. Khoa, M.L. Bui With the advent of RIB facilities, it would be very interesting to measure the ISGMR strength distributions in nuclei far from stability. However these experiments must be done in inverse kinematics and the most appropriate solid target for this is $^{6}$Li; it also meets the requirements for being a good ISGMR probe as it is light, has T=0, and can be made thin enough that recoils can escape to be detected. However, little is known about using $^{6}$Li as a probe for the ISGMR. To that end, ISGMR measurements have been made using a $^{6}$Li probe at 60MeV/A at RCNP, Osaka University, Japan. Small-angle inelastic scattering data were obtained for $^{58}$Ni, $^{90}$Zr, and $^{116}$Sn. The results of the ISGMR strength extraction will be presented. [Preview Abstract] |
Saturday, October 26, 2013 11:42AM - 11:54AM |
PD.00007: Two-neutron decay of excited states of $^{11}$Li Jenna Smith One prominent example of a Borromean nucleus is the two-neutron halo nucleus, $^{11}$Li. All excited states of this nucleus are unbound to two-neutron decay. Many theories propose that the two valence neutrons exhibit dineutron behavior in the ground state, but it is unclear what effect such a structure would have on the decay of the excited states. We have recently completed an experiment designed to study the decay of one of these excited states. Unbound $^{11}$Li was populated via a two-proton knockout from $^{13}$B. The two emitted neutrons were detected with the Modular Neutron Array (MoNA) and the Large-area multi-Institutional Scintillator Array (LISA) in coincidence with the daughter fragment, $^{9}$Li. Preliminary results will be discussed. [Preview Abstract] |
Saturday, October 26, 2013 11:54AM - 12:06PM |
PD.00008: Measurement of Neutron knockout cross-section of $^{24}$O to the ground-state of $^{23}$O Dilupama Divaratne, Carl Brune, Paul King, Harsha Attanayake, Steven Grimes, Michael Thoennessen, Daniel Bazin This research provides an understanding of the structure of the ground state wave-function of $^{24}$O through measuring the neutron knockout cross section of $^{24}$O to the $\frac{1}{2}$$^{+}$ ground state of $^{23}$O. The experiment was conducted at the National Superconducting Cyclotron Laboratory using the S800 spectrograph and 470 mg/cm$^2$ Be reaction target with 92.3 MeV/u $^{24}$O beam energy. The cross section values to the different final states of $^{23}$O along with the related spectroscopic factors will convey to us information regarding how doubly magic $^{24}$O is. Specific details of this investigation, analysis, interpretation of resulting cross sections and parallel and perpendicular momentum of the residual will be discussed. [Preview Abstract] |
Saturday, October 26, 2013 12:06PM - 12:18PM |
PD.00009: Two-Neutron Decay from the Ground State of $^{26}$O Harsha Attanayake, Paul King, Carl Brune, Dilupama Divaratne The study of $^{26}$O is important to understand the behavior and properties of neutron-rich heavy oxygen isotopes. Recent experiments have indicated that $^{24}$O is bound and the tests have failed to find bound states of $^{25}$O and $^{26}$O. Unstable $^{26}$O decays to stable $^{24}$O by emitting two neutrons ($^{26}$O$\rightarrow^{24}$O + 2n) rather than decaying via $^{25}$O, which is neutron unbound with a {\it 1n} separation energy of 770 keV. An investigation of $^{26}$O was conducted at the National Superconducting Cyclotron Laboratory, which possesses the capability to produce rare isotope beams and detect neutrons with an efficiency of about 70\% with the MoNA detector. Production of $^{26}$O was done by one-proton removal from a $^{27}$F beam with an energy of 82 MeV/u impending on a 705 mg/cm$^2$ Be target. Coincidence of the two neutrons with $^{24}$O was measured for four-vector momentum event reconstruction, allowing extraction of the invariant mass of $^{26}$O. [Preview Abstract] |
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