Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session J15: Nuclear Reactions and Astrophysics |
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Sponsoring Units: DNP Chair: Augusto Macchiavelli, Lawrence Berkeley National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis H |
Sunday, April 13, 2008 10:45AM - 10:57AM |
J15.00001: Nuclear Reaction Dynamics of the $^{10}{\rm B}(d,n_0)^{11}{\rm C}$ Reaction Below 160 keV S. Stave, M.W. Ahmed, M.A. Blackston, A.S. Crowell, S.S. Henshaw, C.R. Howell, P. Kingsberry, B.A. Perdue, H.R. Weller, B.L. Doyle, P. Rossi, A.J. Antolak, R.M. Prior, M.C. Spraker Data were taken at TUNL to investigate the plausibility of using low energy deuterons and the $^{10}{\rm B}(d,n)^{11}{\rm C}$ reaction as a source of 6.3 MeV neutrons. An analysis of the data at incident deuteron energies of 160 keV and 140 keV and neutron angles between 0$^{\circ}$ and 150$^\circ$ indicates an $n_0$ neutron cross section that is lower than previous estimates by at least two orders of magnitude. In order to gain insight into the reaction dynamics at these low energies the cross section results have been compared with results from calculations using the distorted wave Born approximation (\textsc{dwuck}) and a detailed Hauser-Feshbach calculation performed by the authors. [Preview Abstract] |
Sunday, April 13, 2008 10:57AM - 11:09AM |
J15.00002: Study of the $^{11}B (\vec{p},\alpha)^8Be$ Reaction using polarized protons below 5.1 MeV. Seth Henshaw, Sean Stave, Mohammad Ahmed, Matthew Blackston, Brent Perdue, Henry R. Weller, Ralph France, Tom Lewis, J.P. Metzker, Richard Prior, Mark Spraker, Alex Kusnezov Cross section and analyzing power data have been obtained for proton energies between 0.4 and 5.1 MeV. The experiment was performed using the TUNL polarized proton beam, eight Silicon-surface barrier detectors, and an enriched $^{11}$B target deposited on a thin carbon backing. Energies below 1.1 MeV were obtained using an Aluminum degrading foil. Preliminary results indicate analyzing powers for the $^{11}B(\vec{p},\alpha_{1})^8Be$* reaction at the $\sim0.675$ MeV resonance which are consistent with zero and a cross section angular distribution which is isotropic. Previous measurements of the absolute angle integrated cross section on top of this resonance have produced results having significant variations. Preliminary results for analyzing powers and cross sections will be presented along with experimental details and possible implications for energy production in an aneutronic $^{11}$B + p fusion reactor. [Preview Abstract] |
Sunday, April 13, 2008 11:09AM - 11:21AM |
J15.00003: Neutron Asymmetry Parameterization of a Dispersive Optical Model Jonathan Mueller, Robert Charity, Lee Sobotka, Willem Dickhoff We have recently applied a Dispersive Optical Model (DOM) analysis to a series of calcium isotopes. The proton spectroscopic factors as a function of asymmetry were determined, but the neutron dependence on asymmetry was not. Consideration of either Gamow-Teller or collective E2 strength yield different asymmetry dependencies (for neutrons) than the global OM parameterizations. Neutron elastic scattering n+48Ca can distinguish between these possibilities. With such data, extrapolation of neutron spectroscopic factors towards the n-drip line will be more robust. [Preview Abstract] |
Sunday, April 13, 2008 11:21AM - 11:33AM |
J15.00004: Survey of Neutron Spectroscopic Factors for \emph{Z}=8 to 28 nuclei Jenny Lee, P. Dai, M. Horoi, W.G. Lynch, S.C. Su, M.B. Tsang, S. Warren Spectroscopic factor (SF) is a fundamental quantity in nuclear physics. SFs are extensively used from nuclear structure to astrophysical network calculations. They provide an important probe to test how well shell models describe the structure of nuclei. In this talk, we will compare neutron spectroscopic factors obtained for the sd shell nuclei, Ca, Ti, Cr and Ni isotopes to shell models. Of particular interests are the comparisons of data with different shell model interactions in these regions including the evolution of single particle states around \emph{Z}=20, \emph{N}=27 and \emph{N}=29 regions. [Preview Abstract] |
Sunday, April 13, 2008 11:33AM - 11:45AM |
J15.00005: Dispersive Optical Model and Isospin S.J. Waldecker, W.H. Dickhoff Dispersive optical model (DOM) analyses successfully describe scattering and bound-state data for $^{40}$Ca, $^{42}$Ca, $^{44}$Ca, and $^{48}$Ca.\footnote{ R.J. Charity, L.G. Sobotka, and W.H. Dickhoff, Phys. Rev. Lett. 97,162503 (2006)}$^{,}$\footnote{ R.J. Charity, J.M. Mueller, L.G. Sobotka, and W.H. Dickhoff, Phys. Rev. C 76, 044314 (2007)} The global fits agree very well with the data, but the extent to which these DOM calculations can be extrapolated to systems not included in the fit is not sufficiently constrained for neutrons. Bound-state data for Ca isotopes show clear trends when analyzed as a function of isospin, suggesting that isospin is an important ingredient to include in any extrapolation. The effects of including explicit isospin dependence in the DOM potentials are explored in this contribution. [Preview Abstract] |
Sunday, April 13, 2008 11:45AM - 11:57AM |
J15.00006: Results of the First TOF Mass Measurements at NSCL M. Matos, A. Estrade, M. Amthor, D. Bazin, A. Becerril, T. Elliot, D. Galaviz, A. Gade, G. Lorusso, J. Pereira, M. Portillo, A. Rogers, H. Schatz, A. Stolz, D. Shapira, E. Smith, M. Wallace Time-of-Flight mass measurements technique, recently developed at the NSCL, MSU, was used to measure masses of exotic neutron-rich nuclides in the Fe region, important for r-process calculations as well as for calculations of processes occurring in the crust of accreting neutron stars. Results from the experiment will be presented and discussed. [Preview Abstract] |
Sunday, April 13, 2008 11:57AM - 12:09PM |
J15.00007: Calculation of Level Densities for Nuclei Far from the Line of Stability Shaleen Shukla, Steven Grimes Nuclear level densities provide crucial input in any statistical model calculation of compound nuclear decay, applied to the various processes like the study of fission hindrance in heavy nuclei, the yields of evaporation residues to populate certain exotic nuclei, production of heavy elements in stellar processes etc. We calculate nuclear level densities for nuclei near the drip line. We use a single fermion model with non interacting fermions and spectral distribution methods which allow moments to be calculated in huge spaces using a fairly small sum. We shall present results some typical results for mass number in the range 40 - 100. We are also investigating the effect of two-body interaction on these nuclei and would also present some results showing its effect. [Preview Abstract] |
Sunday, April 13, 2008 12:09PM - 12:21PM |
J15.00008: Microscopic theory of incorporating resonances in the mean field M.S. Sabra, F.B. Malik Starting from a many body Hamiltonian, containing one and two body operators, a microscopic theory has been developed to incorporate resonances in the mean field for the scattering theory. The results for the elastic scattering will be presented. It indicates that the structure of the S-matrix obtained differs from some of the theories applied on an ad hoc way to describe elastic scattering. The derived theory has been applied to $\alpha -\alpha $ scattering in the energy range 35.0-40.0 MeV (lab), where the phase shift analysis indicates a sudden jump, thereby implying the occurrence of a resonance. The data has been analyzed by incorporating resonance term in the mean field which has its roots in the energy-density functional approach. This leads to improvement of the fits to the data. This analysis will be compared to the analysis obtained by the methods where a resonance term is usually added on an ad hoc way to the optical potential. [Preview Abstract] |
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