Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session MG: Nuclear Structure: Light Nuclei I |
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Chair: Remco Zegers, Michigan State University Room: Peralta |
Saturday, November 6, 2010 8:30AM - 8:42AM |
MG.00001: Understanding $^{3}$He Nuclei via Quasi-elastic $^{3}$He(e,e'd) and $^{3}$3He(e,e'p) Asymmetry Measurements Vincent Sulkosky Two-body calculations using realistic wave-functions predicted that the D(e,e'p) asymmetry varies strongly as a function of missing momentum. This prediction has been tested in quasi-elastic D(e,e'p)n experiments in which the predicted sign change of the asymmetry has been observed when the missing momentum is larger than the Fermi momentum. The $\stackrel{\rightarrow}{\rm{^{3}He}}$($\vec{\rm{e,}}\rm{e'p})$ and $\stackrel{\rightarrow}{\rm{^{3}He}}$($\vec{\rm{e,}}\rm{e'd})$ reaction channels have also been calculated using state-of-the-art Faddeev calculations, and the results indicate that the asymmetry as a function of missing momentum is likewise sensitive to the initial-state wave-function. For Jefferson Lab experiment E05-102, we measured the double spin asymmetries A$_{x}$ and A$_{z}$ in the range of recoil momenta from 0 to $\sim$ 200 MeV/c for the quasi-elastic and x$>$1 $\stackrel{\rightarrow}{\rm{^{3}He}}$($\vec{\rm{e,}}\rm{e'p})$ and $\stackrel{\rightarrow}{\rm{^{3}He}}$($\vec{\rm{e,}}\rm{e'd})$ channels. An overview of experiment will be discussed including an update on the analysis progress. [Preview Abstract] |
Saturday, November 6, 2010 8:42AM - 8:54AM |
MG.00002: Precision measurement of the n-4He scattering length using neutron interferometry M.G. Huber, M. Arif, D.L. Jacobson, D.A. Pushin, M.O. Abutaleb, T.C. Black, C.B. Shahi, F.E. Wietfeldt The NIST neutron interferometer and optics facility (NIOF) is currently performing a precision measurement of the n-4He scattering length to less than 0.3{\%} relative uncertainty. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons entering the interferometer are Bragg diffracted in the blades to produce two spatially separate yet coherent beam paths much like an optical Mach-Zehnder interferometer. A sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths. This phase difference is directly related to the sample's scattering length. Neutron scattering lengths are one parameter that can be predicted using advanced theoretical models describing two and three nucleon interactions. In an effort to provide tests and/or benchmarks of these theoretical models, the NIOF has already performed precision measurements of neutron scattering lengths to less than 1{\%} relative uncertainty in several low Z gases: H, D, 3He, and polarized 3He. A preliminary result of this work will be given. [Preview Abstract] |
Saturday, November 6, 2010 8:54AM - 9:06AM |
MG.00003: Spectroscopic Investigation of Lambda Hypernuclei in the Wide Mass Region by the Reaction (e,e'K) Chunhua Chen The third-generation (\emph{e,e'K$^{+}$}) hypernuclear experiment E05115 at Jlab HallC was carried out in 2009. The goal of the experiment is to obtain high precision spectroscopy for medium-heavy hypernuclei $^{52}_\Lambda$V as well as light p shell hypernuclei $^{12}_\Lambda$B,$^{7}_\Lambda$He,$^{9}_\Lambda$Li and $^{10}_\Lambda$Be. The newly developed HES(High-resolution Electron Spectrometer) was employed in this experiment.Compared to last Jlab HallC hypernuclear experiment which run in 2005, the higher beam energy and brand new electron spectrometer makes the ``tilt method'' work more effectively. In this talk, I will present the experimental setup, the improved spectrometer calibration procedure as well as the preliminary spectrum. [Preview Abstract] |
Saturday, November 6, 2010 9:06AM - 9:18AM |
MG.00004: Spectroscopy of $^{12}$Be using the ($^{7}$Li, $^{7}$Be) reaction in inverse kinematics Rhiannon Meharchand, Sam M. Austin, T. Baugher, D. Bazin, B.A. Brown, J. Deaven, A. Gade, G.F. Grinyer, C.J. Guess, H. Iwasaki, S. McDaniel, K. Meierbachtol, G. Perdikakis, J. Pereira, A.M. Prinke, A. Ratkiewicz, A.J. Signoracci, S. Stroberg, L. Uher, P. Voss, K.A. Walsh, D. Weisshaar, R. Winkler, R.G.T. Zegers, M.E. Howard Charge-exchange reactions have been used extensively in forward kinematics to probe the spin-isospin response of stable nuclei. By exploiting a simple proportionality between the differential cross section and Gamow-Teller strength (B(GT)), one can extract detailed structure information in a model-independent way. This information provides stringent tests of theoretical models. The charge-exchange group at NSCL has developed a technique to expand these tests to exotic nuclei, using the ($^{7}$Li, $^{7}$Be) reaction in inverse kinematics. The $^{12}$B($^{7}$Li, $^{7}$Be) reaction has been employed to study the structure of $^{12}$Be, to elucidate the breakdown of the N=8 shell closure and demonstrate the merit of this new experimental technique. Experimental details and preliminary results are presented. [Preview Abstract] |
Saturday, November 6, 2010 9:18AM - 9:30AM |
MG.00005: A precise determination of the $^{10}$C excited state lifetime C.J. Lister, E.A. McCutchan, R.B. Wiringa, S.C. Pieper, D. Seweryniak, J.P. Greene, P.F. Bertone, M.P. Carpenter, C.R. Hoffman, G. Henning, R.V.F. Janssens, T.L. Khoo, T. Lauritsen, S. Shu, G. Gurdal, C.J. Chiara We have come to accept the notion of poorly bound neutrons forming spatially extended halos in light nuclei. However, the charge-conjugated situation involving decoupled protons is far from clear, and presents an interesting test of mirror symmetry and of our understanding of the structure of proton drip-line nuclei. New, precise, experiments interpreted with the help from modern ab-initio and cluster theories can clarify the situation. Specifically, we have used the H($^{10}$B,n)$^{10}$C reaction at 95 MeV to populate the one bound excited state in $^{10}$C at 3354 keV and have measured its lifetime using the Doppler Shift Attenuation Method (DSAM). The use of highly inverse kinematics, a variety of targets and backing materials, the Gammasphere array, and the Fragment Mass Analyzer, all helped reduce and quantify systematic uncertainties. We extract a mean lifetime of tau=219+-5$_{(stat)}$+- 8$_{(sys)}$ fs, very close to the lifetime of the $^{10}$Be analog state and at a level of precision that really challenges contemporary nuclear models. The meaning of this observation will be discussed. This research was supported by the DOE Office of Nuclear Physics under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Saturday, November 6, 2010 9:30AM - 9:42AM |
MG.00006: Properties of 12C Resonances Near the Triple Alpha Threshold Martin Alcorta The structure of 12C is a long-standing problem in nuclear physics. Cluster correlations are known to strongly influence the lowest states, which makes this nucleus a challenge to theory. The three-alpha continuum is low in energy and therefore only two bound states exist while the lowest resonances decay into three alpha-particles. Until recently it was not possible to completely characterize these decays and therefore fully explore these lowest resonances. A complete kinematics study of the 10B(3He,paaa) and 11B(3He,daaa) reactions has been performed to study the multi-particle break-up of 12C resonances above the triple- alpha threshold. The energy and widths of various states above the triple-alpha threshold up to 15 MeV have been determined with greater accuracy and in some cases with discrepancies from literature values. The detection of the individual alpha particles allows us to extract partial alpha widths of the natural parity resonances. The ghost peak of the 8Be ground state was included in the extraction of the partial alpha widths and was found to have a significant effect on the partial alpha widths of states just above the triple-alpha threshold. In this contribution the properties of resonances in 12C will be presented and variations from literature values will be discussed. The partial alpha widths will be presented and compared to theory. [Preview Abstract] |
Saturday, November 6, 2010 9:42AM - 9:54AM |
MG.00007: ABSTRACT WITHDRAWN |
Saturday, November 6, 2010 9:54AM - 10:06AM |
MG.00008: Spectroscopy of neutron-unbound fluorine isotopes G. Christian, N. Frank, S. Ash, M. Warren, A. Gade, A. Spyrou, M. Thoennessen, T. Baumann, G.F. Grinyer, D. Weisshaar, P.A. DeYoung Knockout reactions from a beam of $^{29}$Ne at $\sim $60 MeV/u were used to populate the neutron-unbound ground state of $^{28}$F, as well as unbound excited states in other neutron-rich Fluorine isotopes. These unbound excited states decay through the emission of one or more neutrons, which were detected near zero degrees in the MoNA plastic scintillator array. The remaining charged fragments were deflected by the Sweeper dipole magnet, and their kinematic properties were measured in detectors behind the magnet. The decay energy was then calculated from the measured energies and angles of the neutrons and the fragments. In addition, coincident gamma-rays were measured at the target location using the recently commissioned CAESAR CsI array. The gamma-ray tagging was used to determine whether the neutron decayed to the ground state or an excited state of the daughter nucleus. Preliminary results of the analysis, including neutron decay energy spectra, will be presented. [Preview Abstract] |
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