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 E14: Theory Involving Finite Nuclei |
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Sponsoring Units: DNP Chair: Witold Nazarewicz, University of Tennessee Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis G |
Saturday, April 12, 2008 3:30PM - 3:42PM |
E14.00001: Spectroscopy of $^7_{\Lambda}$He hypernucleus in three-body model Branislav Vlahovic, Vladimir Suslov, Igor Filikhin The $^7_{\Lambda}$He hypernucleus is considered as three-body cluster system $^5_{\Lambda}$He+$N$+$N$ [1]. Configuration space Faddeev calculations are performed for the hyperon binding energy. In particular we obtained the binding energy 5.35 MeV, which agrees with preliminary theoretical predictions (5.4 MeV) [2]. Note that this value differs from the recent experimental data [3]. Discussed is the recipe for extracting hyperon binding energy from the three-body calculations. The value obtained in previous E. Hiyama's et al.[4] calculation has to be corrected. A variant of the method of analytical continuation in coupling constant is applied to calculate the energies of resonance levels of the $^7_{\Lambda}$He. The second bound state of $^7_{\Lambda}$He with total angular momentum $J=3/2^+(5/2^+)$ was found. The bound states and low-lying resonances of $^7_{\Lambda}$He can be classified as an analog of the $^6$He ground band. 1. I. Filikhin, V. M. Suslov and B. Vlahovic, J. Phys. G31 389 2005. 2. O. Hashimoto, HYP2006 Mainz, October 11-14, 2006. 3. L. Tang, {\it Spectroscopy of $\Lambda$-Hypernuclei by Electroproduction, HNSS/HKS Experiments at JLAB}, FB18, Brazil, August 21-26 (2006); http://www.fb18.com.br 4. E. Hiyama, et al., PRC53 2078 1996. [Preview Abstract] |
Saturday, April 12, 2008 3:42PM - 3:54PM |
E14.00002: Full configuration interaction calculations of light nuclei Pieter Maris, James Vary, Andrey Shirokov We perform full configuration interaction (FCI) calculations for light nuclei with a realistic NN interaction, JISP16. We obtain ground state energies and their uncertainties through an exponential extrapolation that we demonstrate is reliable in testcases up to A=4 where fully converged results are obtained. For heavier nuclei, up through Carbon-12, we obtain ground state energies converged to a few percent. In addition to the energies, we also calculate selected observables such as rms radii and quadrupole moments. [Preview Abstract] |
Saturday, April 12, 2008 3:54PM - 4:06PM |
E14.00003: Nuclear shell structure in anharmonic oscillator potential F. Bary Malik, Anup Majumder The studies of binding energies of light and medium-light nuclei have established anomalous trend of shell structure compared to the one expected in the case of isotropic harmonic oscillator for nuclei away from the valley of stability and close to the drip lines. We have, therefore, studied the nature of the shell-gap expected in anharmonic three dimensional oscillator potential with a spin-orbit and 1.1 term. The energy gaps among minor shells are strongly dependent on the degree of anisotropy and the strength of the spin-orbit coupling. Many of the anomalous gaps e.g. large gap for N = 14 and dwindling gap for N = 8 could be ascribed to anisotropic harmonic mean field. Thus, many of the exotic nuclei seem to have large deformation and need to be treated with anisotropic harmonic basis set or described by rotational model with rotational-particle coupling. Typical level scheme as a function of anharominicity will be presented. [Preview Abstract] |
Saturday, April 12, 2008 4:06PM - 4:18PM |
E14.00004: Possible Angular Momentum Dependence of Dissipation in Nuclear Fission Wei Ye, Jan Toke, W. Udo Schroeder A comparative analysis of the pre-scission neutron multiplicities observed in a new experiment [1] and one reported earlier [2] suggests that, besides known deformation [3] and temperature [4] dependencies, nuclear dissipation in fission may have an angular momentum dependence. The analysis based on a Langevin equation coupled with a statistical decay model [3] considers angular momentum effects on fission dynamics. Pre-saddle reduced dissipation coefficients of $\beta$ = $2 \times 10^{21}s^{-1}$ and $3 \times 10^{21}s^{-1}$ have been extracted for the matched reactions $^{16}$O + $^{181}$Ta and $^{19}$F + $^{178}$Hf [1],respectively. The difference in the extracted $\beta$ values is attributed to the difference in the angular momenta contributing to the fission process in the two reactions. Work attempting to derive a quantitative expression for an angular momentum dependence of the dissipation strength is in progress. [1] H.Singh et al., Phys. Rev. C76 (2007) 044610 [2] L.G.Moretto et al., Phys. Rev. Lett. 75 (1995) 4186; Phys. Rev. C54 (1996) 3062 [3] P.Frobrich and I.I.Gontchar, Phys. Rep. 292(1998) 131 [4] P.Paul and M.Thoennessen, Ann. Rev. Part. Sci. 44(1994) 65 [Preview Abstract] |
Saturday, April 12, 2008 4:18PM - 4:30PM |
E14.00005: Effective Shell-Model interactions for the p-shell from the No-Core Shell Model A.F. Lisetskiy, M.K.G. Kruse, B.R. Barrett, P. Navratil, I. Stetcu, J. Vary The {\em ab initio} no-core shell model (NCSM) is a powerful many-body technique to perform fundamental microscopic studies of the structure of light nuclei. However, it becomes rather challenging to produce converged results for nuclei with A $\geq$ 12. In this contribution, following the idea of Ref. [2] we derive effective p-shell Hamiltonians from $N_{\rm max} \hbar \Omega$ NCSM calculations for $^6$Li with $N_{\rm max} =2,4,...,14$. We show how the averaged many-body correlations modify the p-shell two-body Hamiltonian and explore the dependence of the effective one-body and two-body matrix elements on $N_{\rm max}$. We present the results of the standard shell model calculations using derived effective Hamiltonian for p-shell nuclei with $A>6$ and compare it to the exact NCSM results. \newline [2] P.Navratil, M.Thoresen, and B.R.Barrett, Phys.Rev.C. {\bf 55}, R573 (1997). [Preview Abstract] |
Saturday, April 12, 2008 4:30PM - 4:42PM |
E14.00006: Effective Shell-Model interactions for $^{18}$F from the No-Core Shell Model M.K.G. Kruse, A.F. Lisetskiy, B.R. Barrett, P. Navratil, I. Stetcu, J.P. Vary Insight gained from projected No Core Shell Model calculations in the p-shell can now be utilized to obtain information about and to construct effective Shell Model two-body matrix elements (TBMEs) for heavier nuclei. Here we report on a NCSM investigation in $6 \hbar \Omega$ model space for $^{18}$F in order to determine effective TBMEs for the sd-shell. These matrix elements accurately account for the many-body correlations present in the original large space and can be compared to the empirical (or theoretical) TBMEs employed in a traditional core shell-model calculation. Results for other effective operators, specifically electromagnetic, will also be presented. [Preview Abstract] |
Saturday, April 12, 2008 4:42PM - 4:54PM |
E14.00007: Projected Configuration Interaction Method for Heavy Nuclei Mihai Horoi, Zaochun Gao The nuclear Configuration Interaction (CI) method using a spherical single particle (s.p.) basis has been very successful in describing the properties of the low-lying states of the light and medium size nuclei. The main shortcoming of this methods is related to the exploding dimensions that could make the calculations unfeasable even when one changes the number of nucleons and/or s.p. states by one unit. In addition, the relation of the correlated spherical wave functions to the mean field picture is either indirect or very difficult to make. The Projected Configuration Interaction (PCI) method starts from a collection of mean-field wave functions, and builds up correlated wave functions of good symmetry. It relies on the Generator Coordinator Method (GCM) techniques, but it improves the past approaches by a very efficient method of selecting the basis states. We compare the results of this method with the results of the full CI calculations in the $sd$ and $fp$ shell, as well as with the standard GCM, the Quantum Monte Carlo Diagonalization (QMCD) method (e.g. Phys. Rev. C {\bf 59}, R1846 (1999)), and the complex MONSTER/VAMPIR method (e.g. Nucl. Phys A {\bf 571}, 77 (1994)). [Preview Abstract] |
Saturday, April 12, 2008 4:54PM - 5:06PM |
E14.00008: Checker Board Model Theodore Lach The Checker Board Model (CBM) is a 2D model of the nucleus that proposes that the synchronization of two outer rotating quarks in the nucleons accounts for magnetic moment of the nucleons and that the resulting magnetic flux couples (weaves) into the 2D checker board array structures and this 2D magnetic coupling in addition to electrostatic forces of the two rotating and one stationary quark accounts for the apparent strong nuclear force. The symmetry of the He nucleus helps explain why this 2D structure is stable. This model explain the mass of the proton and neutron, along with their magnetic moments and their absolute and relative sizes and predict the masses of two newly proposed quarks $^{(1)}$: the ``up'' and the ``dn'' quarks. Since the masses of the ``up'' and ``dn'' quark determined by the CBM (237.31 MeV and 42.392 MeV respectively) did not fit within the standard model as candidates for u and d, a new model (New Physics) had to be invented. The details of this new nuclear physics model can be found at: http://checkerboard.dnsalias.net/ (1). T.M. Lach, Checkerboard Structure of the Nucleus, Infinite Energy, Vol. 5, issue 30, (2000). (2). T.M. Lach, Masses of the Sub-Nuclear Particles, nucl-th/0008026, @http://xxx.lanl.gov/ [Preview Abstract] |
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