Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session CD: Nuclear Structure I |
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Chair: Vladimir Gudkov, University of South Carolina Room: Patio |
Thursday, October 25, 2012 8:30AM - 8:42AM |
CD.00001: The Mesonic and Nonmesonic Decay Rates of the $_{\Lambda}$He$^{4}$ Shalva Tsiklauri, Joel Hernandez We calculated the lifetime and the mesonic and nonmesonic decay rates of the four body $_{\Lambda }$He$^{4}$ Hypernucleus by using Hyperspherical Functions method in momentum space for different Nucleon-Nucleon and Lambda Nucleon effective potentials. The effects of final-state interactions and possible three body $\Lambda {\rm N}{\rm N}$ decay contributions were studied in the context of a simple model of nucleon-stimulated decay. [Preview Abstract] |
Thursday, October 25, 2012 8:42AM - 8:54AM |
CD.00002: Investigation of $\alpha$-resonances in $^{10}$Be using $^6$He($\alpha,\alpha$)$^6$He Anthony Kuchera, G.V. Rogachev, J.C. Blackmon, I. Wiedenhoever, L.T. Baby, J.A. Belarge, E.D. Johnson, E. Koshchiy, J. Lai, L.E. Linhardt, K. Macon, M. Matos, D. Santiago-Gonzalez Numerous theoretical and experimental studies have shown the importance of clustering in light nuclei [1]. The Be isotopes have been of particular interest recently due to their exotic two-core $\alpha+\alpha+$ valence neutrons configurations [2,3,4,5]. Experimentally, ($\alpha,\alpha$) reactions are prime tools for studying these structures. In this work, the $^{6}$He$+\alpha$ excitation function in the range of 10 to 18.5 MeV was measured. The $^6$He beam was produced with the RESOLUT radioactive beam facility at FSU. Measurements were performed using the active target detector ANASEN [6]. Parameters of the observed states were determined by an R-Matrix analysis. The properties of these resonances in $^{10}$Be will be discussed.\\[4pt] [1] M. Freer, Rep. Prog. Phys. 70, 2149 (2007).\\[0pt] [2] A. Dote, H. Horiuchi, and Y. Kanada-Enyo, Phys. Rev. C 56, 1844 (1997).\\[0pt] [3] N. Itagaki and S. Okabe, Phys. Rev. C 61, 044306 (2000).\\[0pt] [4] Y. Ogawa, K. Arai, Y. Suzuki, and K. Varga, Nucl. Phys. A 673, 122 (2000).\\[0pt] [5] M. Freer, et al., Phys. Rev. Lett. 96, 042501 (2006).\\[0pt] [6] M.Matos, et al., Proc. Intern. Symposium on Nuclei in the Cosmos XI, July 2010, Heidelberg, Germany, p.226 (2010). [Preview Abstract] |
Thursday, October 25, 2012 8:54AM - 9:06AM |
CD.00003: Spin doublet $(1^-,2^-)$ of ${ }_\Lambda ^6 $He within three-body cluster model Vladimir Suslov, Igor Filikhin, Branislav Vlahovic The spin doublets $(1^-,2^-)$ of ${ }_\Lambda ^6 $He are of great interest for testing theoretical models of the hyperon-nucleon interaction. The experimental value -0.17 MeV is known for the binding energy of the state $1^-$ (singlet spin state) of ${ }_\Lambda ^6 $He [1]. The experimental data for the $2^-$ state (triplet spin state) were not yet reported. Theoretical considerations for the state $2^-$of ${ }_\Lambda ^6 $He have been attempted by Motoba et al. [2] and Hiyama et al. [3]. Indirect prediction for this state has been given in [4]. Results obtained in these works are quite different. Our goal is to obtain a new prediction for the hyper nucleus $_\Lambda ^6 $He, which is considered as the cluster system$\alpha n\Lambda $, by using new proposed potentials for$\alpha \Lambda $and $\alpha n$ interactions [5]. Our cluster calculation is based on the configuration-space Faddeev equations for a system of three non-identical particles. The energies of the ($1^-2^-)$ spin doublets are calculated for different $n\Lambda $ and $\alpha \Lambda $ potentials [4-6]. Our results are compared with those from other calculations and experimental data. \\[4pt] [1] L. Majling, Proc. Natl. Conf. on Phys. of Few-Body and Quark-Hadronic Syst. (Kharkov, Ukraine, 1992). \\[0pt] [2] T. Motoba et al. Prog. Theor. Phys. \textbf{70} 189 (1983). \\[0pt] [3] E. Hiyama et al. Phys. Rev. C \textbf{59} 2351 (1999). \\[0pt] [4] I. Filikhin, et al. J. Phys. G: \textbf{31}, 389 (2005). \\[0pt] [5] I. Filikhin et al. EPJ Web of Conferences \textbf{3}, 07004 (2010); \\[0pt] [6] I. Filikhin, A. Gal, Phys. Rev. C \textbf{65} 041001R (2002). [Preview Abstract] |
Thursday, October 25, 2012 9:06AM - 9:18AM |
CD.00004: Study of Neutron Deficient $^{9}$C 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 [1,2]. 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 carbon isotope, $^{9}$C, through $^{8}$B+p resonance scattering using the new active target detector ANASEN [3]. The experiment was performed at the John D. Fox Superconducting Accelerator Laboratory at FSU. A rare isotope beam of $^{8}$B ions was produced using the radioactive nuclear beam facility RESOLUT. Pure hydrogen 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+$^{8}$B excitation functions was performed using the R-Matrix approach. The preliminary results will be presented.\\[4pt] [1] A. Volya, Phys. Rev. C $\bf{79}$, 044308 (2009).\\[0pt] [2] S. Quaglioni and P. Navr\'atil, PRL \textbf{101}, 092501 (2008).\\[0pt] [3] M. Matos, et al.,Proc. Intern. Symposium on Nuclei in the Cosmos XI, July 19-23 2010, Heidelberg, Germany, p.226(2010). [Preview Abstract] |
Thursday, October 25, 2012 9:18AM - 9:30AM |
CD.00005: The controversial $^{10}$He ground state resonance: A new observation using a 2p2n-removal from $^{14}$Be Z. Kohley, J. Snyder, M. Thoennessen A 2p2n-removal reaction from a $^{14}$Be beam was used to populate the two-neutron unbound $^{10}$He. A triple coincidence measurement of the $^{8}$He+n+n system, using the Modular Neutron Array (MoNA) and the Sweeper magnet, allowed for the ground state resonance of $^{10}$He to be reconstructed. Using a detailed Monte Carlo simulation, the resonance was fit with a Breit-Wigner lineshape having an energy of 1.60(25) MeV and width of 1.8(4) MeV. This result is in good agreement with previous measurements using 1-proton knockout reactions from $^{11}$Li, yet differs from experiments which used transfer reactions to populating $^{10}$He. The implications of this result, using the $^{14}$Be(-2p2n) reaction mechanism, with respect to the previous $^{10}$He measurements will be discussed. [Preview Abstract] |
Thursday, October 25, 2012 9:30AM - 9:42AM |
CD.00006: Electric Dipole strengths in $^{11}$Be Elaine Kwan Conventional nuclear structure and properties are known to change as nuclei become more neutron rich. Light nuclei near the neutron drip line are of interest theoretically and experimentally since they exhibit unique features not observed elsewhere. The one neutron halo nucleus $^{11}$Be has the fastest known $E1$ transition between bound states with a strength $\sim$0.1 $e^2$fm$^2$, an inverted parity, and contains few nucleons that it can be calculated theoretically based on first principles. Large $E1$ strength to the continuum has also been observed. Accuracies of $\sim$10\% for the $B(E1)$ between the bound states and $\sim$5\% to the continuum have been measured, but with discrepancies of ~15\% between the reported strengths for the latter. Improvement to the precisions of the $B(E1)$ values will help isolate the importance of individual N-N interactions included in theory. The first low-energy Coulomb excitation experiment on $^{11}$Be was recently carried out at TRIUMF using the TIGRESS/BAMBINO array to measure the $E1$ strengths. A semi-classical reaction model and quantum mechanical calculation using the extended continuum discretized coupled channels model were used to determine the $B(E1)$ strengths. Preliminary results will be presented. [Preview Abstract] |
Thursday, October 25, 2012 9:42AM - 9:54AM |
CD.00007: Measurement of the $\beta$-branch of $^{12}$B to the Hoyle state in $^{12}$C Martin Alcorta, M. Albers, S. Almaraz-Calderon, P.F. Bertone, M.P. Carpenter, B. DiGiovine, J.P. Greene, C.R. Hoffman, R.V.F. Janssens, T. Lauritsen, C. Nair, K.E. Rehm, D. Seweryniak, S. Zhu, H.O.U. Fynbo, K.L. Laursen, P.F.F. Carnelli, S.T. Marley, C. Ugalde Recent measurements of the $\beta$-branch of $^{12}$B to the Hoyle state give 0.58(2)\%, in contradiction with the value found in the literature of 1.2(3)\%. The precise branching ratio to the Hoyle state is important for understanding the R-Matrix fits of excitation energies in $^{12}$C between 9-13 MeV from studies of $\beta$-delayed triple-alpha decay. Accurate fits to the data are crucial in order to fully disentangle the different states of natural spin and parity in the region. In order to obtain an independent measurement of the $\beta$-branch, we have measured the $\gamma$-branch of the Hoyle state (a cascade going through the 4.44 MeV 2$^+$ state) using the Gammasphere array at ATLAS. The measured value of the $\beta$-branch as well as the implications of the results will be presented. [Preview Abstract] |
Thursday, October 25, 2012 9:54AM - 10:06AM |
CD.00008: Study of 13B(d,p)14B Reaction in Inverse Kinematics with Helios S. Bedoor, A.H. Wuosmaa, J.C. Lighthall, S.T. Marley, D.V. Shetty, M. Alcorta, B.B. Back, P.F. Bertone, K.E. Rehm, A.M. Rogers, J.P. Schiffer, B.A. Brown, C.M. Deibel The $^{14}$B nucleus was studied employing the $(d, p)$ reaction in inverse kinematics using HELIOS at the ATLAS facility at ANL. A beam of $^{13}$B with energy 15.7 MeV/nucleon was produced using the In-Flight method. Protons from the $^{13}$B$(d, p)$$^{14}$B reaction were detected and analyzed using the HELIOS device. Detecting and identifying the recoiling $^{13}$B and $^{14}$B nuclei in a silicon $\Delta$E-E telescope at forward angles distinguished bound and unbound states in $^{14}$B. Angular-momentum transfers and relative spectroscopic factors were deduced for the four lowest states in $^{14}$B. The ground and first excited states, 2$^-$ and 1$^-$ respectively, are presumably made up of $\pi$(0p$_{3/2}$)-$\nu$(1s$_{1/2}$) configurations, while coupling of the proton hole to a d$_{5/2}$ neutron produces (1,2,3,4)$^-$. The 0d$_{5/2}$-1s$_{1/2}$ splitting in $^{14}$B is expected to be small, producing mixing between the (1,2)$^-$ $\ell$ = 0 and 2 configurations. The measured spectroscopic factors for neutron transfer will be compared to the predictions of the shell model calculations. [Preview Abstract] |
Thursday, October 25, 2012 10:06AM - 10:18AM |
CD.00009: Spectroscopy of neutron-unbound $^{15}$Be Jesse Snyder, Michael Thoennessen, Thomas Baumann, Artemis Spyrou, Michael Strongman, Greg Christian, Shea Mosby, Michelle Mosby, Jenna Smith, Anna Simon, Bryan Luther, Sharon Stephenson, Alex Peters, Paul DeYoung, Eric Lunderberg, Joseph Finck A (d,p) reaction was used to populate neutron unbound states in $^{15}$Be from a secondary beam of $^{14}$Be at 55 MeV/u impinging upon a deuterated polyethylene target. The unbound states in $^{15}$Be decayed though the emission of a neutron. The neutron was detected using MoNA, an array of 144 plastic scintillator bars. The charged $^{14}$Be fragments were deflected by the Sweeper dipole magnet into a system of charged particle detectors which allow the reconstruction of their kinematic properties. The decay energy was calculated through invariant mass analysis, using the energy and momentum information of the neutron and fragment at the target. Results will be presented. [Preview Abstract] |
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