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 FF: Nuclear Theory III |
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Chair: Edward Tomusiak, University of Victoria Room: Garden III |
Thursday, October 25, 2012 4:00PM - 4:12PM |
FF.00001: Microscopic calculation of the pre-scission energy in nuclear fission Walid Younes During the latter stages of fission, the energy available to the parent nucleus is divided between the kinetic energy of the nascent fragments, and their internal excitation energy. Accounting for this energy partition remains an open problem in the quantum many-body description of the fission process, and a crucial step in linking microscopic calculations of fission to experimental data. Using a time-dependent generator-coordinate approach, we have calculated the contribution to the kinetic versus excitation energy partition due to the coupling between collective degrees of freedom. We present calculations of this pre-scission energy partition for a fissioning nucleus in the descent from saddle to scission. [Preview Abstract] |
Thursday, October 25, 2012 4:12PM - 4:24PM |
FF.00002: Exploring R-matrix ideas for the description of one-nucleon transfers to resonance states Jutta E. Escher, Akram M. Mukhamedzhanov, Ian J. Thompson Deuteron-induced reactions, in particular (d,p) one-neutron transfer reactions, have been used for decades to investigate the structure of nuclei. These reactions, carried out in inverse kinematics, will play a central role in the study of weakly-bound systems at modern radioactive beam facilities. While the theoretical framework and its computational implementation for describing (d,p) reactions have seen much progress over the decades, open questions remain and need to be addressed, including the proper treatment of transfers to resonance states. Recently, Mukhamedzhanov [PRC 84, 044616 (2011)] proposed a novel approach that describes transfers to both bound and resonance states. The new formalism, which is general enough to include deuteron breakup, formulates the cross section in terms of a dominant surface term that can be expressed in terms of R-matrix parameters. Here we test some of the ideas underlying the proposed formalism, compare calculations to measured cross sections, and discuss implications. [Preview Abstract] |
Thursday, October 25, 2012 4:24PM - 4:36PM |
FF.00003: ABSTRACT WITHDRAWN |
Thursday, October 25, 2012 4:36PM - 4:48PM |
FF.00004: Testing the spin-cutoff factor in shell-model level densities William Spinella, Calvin Johnson The spin-cutoff factor is a standard parameterization for the angular momentum dependence of the nuclear level density. We test how good it is by diagonalizing shell-model Hamiltonians for a variety of sd- and pf-shell nuclides and looking at excited states up to 10 MeV. In general we find it is a very good approximation. [Preview Abstract] |
Thursday, October 25, 2012 4:48PM - 5:00PM |
FF.00005: The origin of order in random matrices with symmetries Calvin Johnson From Noether's theorem we know symmetries lead to conservation laws. What is left to nature is the ordering of conserved quantities; for example, the quantum numbers of the ground state. In physical systems the ground state is generally associated with ``low'' quantum numbers and symmetric, low-dimensional irreps, but there is no a priori reason to expect this. By constructing random matrices with nontrivial point-group symmetries, I find the ground state is always dominated by extremal low-dimensional irreps. Going further, I suggest this explains the dominance of $J=0$ g.s. even for random two-body interactions. [Preview Abstract] |
Thursday, October 25, 2012 5:00PM - 5:12PM |
FF.00006: Solution of the Schroedinger Eq. containing a Perey-Buck nonlocality George Rawitscher, Joseph Power, Mahmoud Jaghoub This type of nonlocality requires the solution of a differential-integral equation that is cumbersome to achieve with finite difference methods. We have developed two different methods that render the solution easy to obtain. One (1) transforms the equation into a corresponding Lippmann-Schwinger integral equation that is solved by a spectral Chebyshev expansion method [1]. The second (2) uses a finite element Galerkin approach, using discrete variable representation Lagrange basis functions in each partition with Gauss-Lobato support points [2]. Both methods agree to within 1:10$^{-9}$ in the evaluation of a scattering problem and require a fraction of a second on a conventional desktop computer. We consider this a significant step forward in the consideration of nonlocalities.\\[4pt] [1] G. Rawitscher, Nucl. Phys. A 886, 1 (2012); \\[0pt] [2] T. N. Resigno and C. W. McCurdy, Phys. Rev. A 62, 032706 (2000). [Preview Abstract] |
Thursday, October 25, 2012 5:12PM - 5:24PM |
FF.00007: Every Nucleus, When Created, Will Exhibit No Motion or Linear, Rotational and/or Vibrational Motion Which May Later Become Modified By Outside Forces Stewart Brekke Due to the excess energy of creation a newly created nucleus may exhibit linear, rotational and/or vibrational motion. For example, in nuclear decay $m_Pc^2 + 1/2m_Pv_P^2 + 1/2I_P\omega_P^2 + 1/2k_Px_P^2 = m_Dc^2 + 1/2m_Dv_D^2 + 1/2I_D\omega_D^2 + 1/2k_Dx_D^2 +$ (particle mass-energy equivalence, linear, rotational and vibrational energies). In another nuclear reaction $m_1c^2 + 1/2I_1\omega_1^2 + 1/2k_1x_1^2 + m_2c^2 + 1/2m_2v_2^2 + 1/2I_2\omega_2^2 + 1/2k_2x_2^2 = m_3c^2 + 1/2m_3v_3^2 + 1/2k_3x_3^2 +...+m_nc^2 + 1/2m_nv_n^2 + 1/2I_n\omega_n^2 + 1/2k_nx_n^2.$ [Preview Abstract] |
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