Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session X7: Nuclear Theory I |
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Sponsoring Units: DNP Chair: Mark Caprio, University of Notre Dame Room: 201 |
Tuesday, April 8, 2014 10:45AM - 10:57AM |
X7.00001: Scaling properties of the harmonic oscillator basis calculations for $N = Z$ nuclei in the infrared limit with the JISP16 potential Chrysovalantis Constantinou, Mark A. Caprio, James P. Vary, Pieter Maris It has recently been found [S. A. Coon \textit{et al.}, Phys. Rev. C 86, 054002 (2012)] that when no-core configuration interaction (NCCI) calculations of low-mass nuclei are plotted against an infrared momentum cutoff $\lambda_{\textrm{sc}}$ (scaling cutoff), a universal curve is obtained for the energy and the RMS radius. The plotted results must have an ultraviolet (UV) cutoff $\Lambda_{UV}$ greater than or equal to the intrinsic cutoff $\Lambda_{NN}$ of the interaction. This assures that UV convergence is reached. The scaling property then allows for the performance of extrapolations in the IR limit. Here we conduct NCCI calculations in the harmonic oscillator basis with the JISP16 potential. In the IR limit we obtain universal curves for $N = Z$ nuclei up to and including $^{8} \mathrm{Be}$. An extrapolation in the IR limit for the ground state energy and the RMS radius is performed, and extrapolated results are obtained. [Preview Abstract] |
Tuesday, April 8, 2014 10:57AM - 11:09AM |
X7.00002: Global performance of covariant energy density functionals: ground state observables of even-even nuclei and error estimates Sylvester Agbemava, A.V. Afanasjev, D. Ray, P. Ring Covariant density functional theory [1] is a modern theoretical tool for the description of nuclear structure phenomena. In this theory, the nucleus is described as a system of nucleons which interact by the exchange of various mesons. The goal of the current investigation is a first ever global assessment of the accuracy of the description of physical observables related to the ground state properties of even-even nuclei and establishing theoretical uncertainties in their description using the set of four modern covariant energy density functionals (CEDF) such as NL3*, DD-ME2, DD-ME$\delta$ and DD-PC1. Calculated binding energies, the deformations, radii and two-particle separation energies are compared in a systematic way with available experimental data [2,3]. The comparison of theoretical results obtained with these CEDFs allows to establish theoretical uncertainties in the description of physical observables in known regions of nuclear chart and extrapolate them towards neutron-drip line.\\[4pt] [1] D.\ Vretenar {\it et al}, Phys.\ Rep. {\bf 409}, 101 (2005).\\[0pt] [2] S.\ Agbemava, A.\ V.\ Afanasjev, D.\ Ray, and P.\ Ring, submitted to Phys. Rev. C.\\[0pt] [3] A.\ V.\ Afanasjev, S.\ Agbemava, D.\ Ray, and P.\ Ring, Phys.\ Lett. B 726, 680 (201). [Preview Abstract] |
Tuesday, April 8, 2014 11:09AM - 11:21AM |
X7.00003: Reflection asymmetric shapes in covariant density functional theory A.V. Afanasjev, S. Agbemava, P. Ring Reflection asymmetric (octupole deformed) shapes play an important role in some areas of nuclear chart. For example, the outer fission barriers in actinides and superheavy nuclei are strongly affected by such shapes [1]. The recent progress in the study of such shapes and octupole softness at ground states of lanthanides ($A\sim 145$) and actinides ($A\sim 224$) as well as at outer fission barriers of actinides and superheavy [1] nuclei within the covariant density functional theory [2] will be reviewed. New results obtained within the relativistic Hartree-Bogoliubov framework with separable limit of finite range Gogny D1S pairing in the pairing channel will be discussed. The experimental data will be systematically compared with model calculations. The work on the extension of the relativistic Hartree-Bogoliubov formalism to the description of odd, odd-odd and rotating nuclei with reflections asymmetric shapes is currently in progress. New results obtained with these extensions will be reported. \\[4pt] [1] H.\ Abusara, A.\ V.\ Afanasjev and P.\ Ring, Phys.\ Rev. C85, 024314 (2012). \\[0pt] [2] D.\ Vretenar, A.\ V.\ Afanasjev, G.\ A.\ Lalazissis, and P.\ Ring, Phys.\ Rep. {\bf 409}, 101 (2005). [Preview Abstract] |
Tuesday, April 8, 2014 11:21AM - 11:33AM |
X7.00004: Building Relativistic Mean-Field Models for Atomic Nuclei and Neutron Stars Wei-Chia Chen, Jorge Piekarewicz Nuclear energy density functional (EDF) theory has been quite successful in describing nuclear systems such as atomic nuclei and nuclear matter. However, when building new models, attention is usually paid to the best-fit parameters only. In recent years, focus has been shifted to the neighborhood around the minimum of the chi-square function as well. This powerful {\it covariance analysis} is able to provide important information bridging experiments, observations, and theories. In this work, we attempt to build a specific type of nuclear EDFs, the relativistic mean-field models, which treat atomic nuclei, nuclear matter, and neutron stars on the same footing. The application of covariance analysis can reveal correlations between observables of interest. The purpose is to elucidate the alleged relations between the neutron skin of heavy nuclei and the size of neutron stars, and to develop insight into future investigations. [Preview Abstract] |
Tuesday, April 8, 2014 11:33AM - 11:45AM |
X7.00005: Examining nuclear pairing correlations in the continuum via a Monte Carlo algorithm Mark Lingle, Alexander Volya Pairing correlations and pair scattering into the continuum of reaction states play an important role in determining the properties of exotic, near dripline nuclei. Unfortunately, the particle number non-conservation and problems in the limit of weak pairing make the traditional approaches based on the BCS theory ill suited for exploration of these near-dripline nuclei. In this presentation we put forth a Monte Carlo algorithm that suffers none of the drawbacks of traditional theories. The advantages of the Monte-Carlo approach include the ability to handle truly large-scale problems exactly, the absence of the fermionic sign problem, and a probabilistic interpretation of quantum-mechanical amplitudes. Excited states corresponding to pair vibrations are also accessible with this approach. We apply our algorithm to the problem of pairing correlations that extend into the reaction continuum. We model the continuum of reaction states by placing the system of interest in a large box. Using the resulting set of one-body states the pairing problem is then solved exactly. We present benchmarking and model studies as well as applications to oxygen isotopes. [Preview Abstract] |
Tuesday, April 8, 2014 11:45AM - 11:57AM |
X7.00006: Bjorken-x dependence of many-body correlations in DIS cross section ratios off nuclei Allen Barr, Drew Fustin, Athanasios Petridis Many-body correlations in nuclei determine the behavior of Deep-Inelastic-Scattering (DIS) cross section ratios off heavy over light nuclei especially for Bjorken-x $>$ 1, obtained at Jefferson Laboratory. Such correlations can be described in terms of quark-cluster formation in nuclei due to wave-function overlapping. In clusters (correlated nucleons) the quark and gluon momentum distributions are softer than in single nucleons and extend to x $>$ 1. The probabilities for such clusters are computed using a network-defining algorithm in which the initial nucleon density is either standard Woods-Saxon or is input from lower energy data while the critical radius for nucleon merging is an adjustable parameter. The exact choice of critical radius depends on the specific nucleus and it is anti-correlated to the rescaling of the Bjorken-x for bound nucleons. The calculations show that there is a strong dependence of the cross section ratios on Bjorken-x in agreement with the data and that four-body correlations are needed to explain the experimental results even in the range 2 $<$ Bjorken-x $<$ 3. [Preview Abstract] |
Tuesday, April 8, 2014 11:57AM - 12:09PM |
X7.00007: Analytical expression for the functional dependence between complex scattering length and binding energy Quamrul Haider, Lon-chang Liu We derive the analytical expressions that relate the binding energy and half-width of an unstable bound state to the corresponding complex scattering length and vice versa [1]. This analytical dependence is interaction-model independent. It provides a check on the consistency between theoretical calculations (respectively, experimental measurements) of bound-state formation and low-energy scattering for any given particle-target system. Numerical examples are presented for eta-nucleus systems. \\[4pt] [1] Q. Haider and Lon-chang Liu, to appear in Acta Physica Polonica. [Preview Abstract] |
Tuesday, April 8, 2014 12:09PM - 12:21PM |
X7.00008: The Sp(3,$R$) Sympletic Model: a comparison of exact and approximate matrix elements Anna McCoy, Mark Caprio, David Rowe The Sp(3,$R$) symplectic model has a close physical connection to both the microscopic shell model and the collective deformation and rotational degrees of freedom, and it is a natural extension of the Elliot SU(3) model from single-shell to multi-shell dynamics. The Sp(3,$R$) Lie algebra --- which contains the angular momentum operators, the quadrupole and vibrational momentum operators and the quadrupole flow tensor operators --- is the smallest algebra containing both the shell model Hamiltonian and the rotor algebra. In the limit of large number of oscillator quanta, the Sp(3,$R$) algebra contracts to the U(3) boson algebra. For large values of the Casimir operator of the SU(3) subalgebra, the sp(3,$R$) algebra further contracts to the algebra of the collective coupled rotor-vibrator model. The exact Sp(3,$R$) matrix elements, calculated using the vector coherent state method, are compared with approximate matrix elements calculated in the U(3) boson limit. [Preview Abstract] |
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