Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session B7: Nuclear Structure I: A<70 |
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Sponsoring Units: DNP Chair: Alan Wuosmaa, Western Michigan University Room: Grand E |
Saturday, April 30, 2011 10:45AM - 10:57AM |
B7.00001: Resonance Contribution to Radiative Neutron Capture on Lithium-7 Lakma Fernando, Renato Higa, Gautam Rupak We consider the contribution of the $3^+$ resonance state to low energy radiative neutron capture in a recently developed halo effective field theory. The resonance contribution is dominated by the M1 transition that proceeds through the initial $^5P_3$ state to the $2^+$ lithium-8 ground state. We present a model-independent calculation whose parameters are constrained by the known data on the $2^+$ ground state and the $3^+$ resonance state. This calculation~ extends the range of applicability of previous effective field theory calculations. [Preview Abstract] |
Saturday, April 30, 2011 10:57AM - 11:09AM |
B7.00002: Ab Initio No Core Shell Model Calculations for Li Isotopes Robert Cockrell, Pieter Maris, James Vary We perform no-core full configuration calculations for several Lithium isotopes with a realistic NN interaction, JISP16. We calculate binding energies for various states of interest as well as dipole and quadrupole moments and select M1 and E2 transitions. The One Body Density Matrix is used to determine the densities and shapes of the ground state and various excited states of these Lithium isotopes. [Preview Abstract] |
Saturday, April 30, 2011 11:09AM - 11:21AM |
B7.00003: Relativistic Continuum Shell Model Janina Grineviciute, Dean Halderson The $R$-matrix formalism of Lane and Thomas\footnote{A. M. Lane and R. G. Thomas, {\it R-Matrix Theory of Nuclear Reactions}, Reviews of Modern Physics, {\bf 30} (1958) 257} has been extended to the relativistic case so that the many-coupled channels problem may be solved for systems in which binary breakup channels satisfy a relative Dirac equation. The formalism was previously applied\footnote{J. Grineviciute and Dean Halderson, {\it Dirac Oscillators and the Relativistic $R$ Matrix}, Phys. Rev. C {\bf 80} (2009) 044607} to the relativistic impulse approximation $\left(RIA\right)$ and now we applied it to Quantum Hadrodynamics $\left(QHD\right)$ in the continuum Tamm--Dancoff approximation $\left(TDA\right)$ with the classical meson fields replaced by one-meson exchange potentials. None of the published $QHD$ parameters provide a decent fit to the $15N+p$ elastic cross section. The deficiency is also evident in inability of the $QHD$ parameters with the one meson exchange potentials to reproduce the $QHD$ single particle energies. Results with alternate parameters sets are presented. [Preview Abstract] |
Saturday, April 30, 2011 11:21AM - 11:33AM |
B7.00004: Progress and applications of configuration-interaction shell-model code BIGSTICK Plamen Krastev, Calvin Johnson, W. Erich Ormand The configuration-interaction (CI) shell-model, together with two- and three-body interactions, is a powerful tool for understanding properties of light nuclei. The aid of advanced computational resources is of primary importance in such calculations. We report on the latest developments and applications of the CI shell-model code BIGSTICK - an efficient parallel on-the-fly code which solves the nuclear many-body problem with both two- and three-body interactions. The US Department of Energy supported this investigation through Contract Nos. DE-FG02-96ER40985 and DE-FC02- 09ER41587 and through Subcontract No. B576152 of the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Saturday, April 30, 2011 11:33AM - 11:45AM |
B7.00005: Spectroscopy of Neutron Unbound Fluorine Gregory Christian, N. Frank, S. Ash, M. Warren, A. Gade, A. Spyrou, M. Thoennesen, T. Baumann, G.F. Grinyer, D. Weisshaar, P.A. DeYoung Knockout reactions from a beam of 29Ne at $\sim $60 MeV/u were used to populate the neutron-unbound ground state of $^{28}$F, as well as unbound excited states in $^{27}$F. 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. In this talk, an overview of the experimental technique and results of the analysis will be presented. [Preview Abstract] |
Saturday, April 30, 2011 11:45AM - 11:57AM |
B7.00006: Projected Hartree-Fock in a shell model basis Joshua Staker, Calvin Johnson We implement projected Hartree-Fock in a shell model basis and compare against exact numerical results from full space diagonalization. We consider the accuracy of projected Hartree-Fock for the excited state spectrum in the cases of the s - d and p - f fixed parity shells as well as cases of mixed parity in the p - sd shell. The accuracy of valence proton-neutron number configurations are also considered including even-even, odd-odd, and odd-A. [Preview Abstract] |
Saturday, April 30, 2011 11:57AM - 12:09PM |
B7.00007: Anatomy of an Inversion-46Ar Larry Zamick, Shadow Robinson, Yitzhak Sharon Two different interactions give very close results for properties of most even-even Ar isotopes, but for ${ }^{46}$Arthe results diverge. The interactions in question are a). WBT and b). SPDF-U. For ${ }^{42,44,46}$Ar the results are as follows : WBT E(2$_1 $+) (1.29,1.17,1.14) MeV E(2$_2 $+) (2.32,1.80,2.10) MeV g(2$_1 $+) (-.095,-.022,+.100 ) g(2$_2 $+) (.096,.045,-.070) SPDF-U E(2$_1 $+) (1.15,1.09,1.59) MeV E(2$_2 $+) (2.28,1.78,3.77) MeV g(2$_1 $+) (-.084,-.040,+.513) g(2$_2 $+) (+.075,+.346,+.514) To understand the big differences for A=46 we must look to the odd K isotopes. Consider the J=3/2$^+$---J=1/2$^+$ splitting.(MeV) EXPT/WBT/SPDF-U A=43 0.561,1.109,0.672 A=45 0.474, 0.871 ,0.345 A=47 -0.360,0.507,-0.320 A=49 0.200,0.729,0.078 We see that there is an inversion in the ``d$_{3/2} $ - s$_{1/2} $`` splitting for ${ }^{47}$K. The SPDF-U interaction successfully gives this inversion but WBT does not. Things are a bit different for B(E2,0$_1 $-2$_1 )$.The values in e$^2$fm$^4$ are WBT (338,425,541) /SPDF-U (351,357,525). Here the 2 interactions give very similar results. Both interactions yield a larger B(E2) for ${ }^{46}$Ar than for ${ }^{44}$Ar, as do previous calculations by others. This despite the fact that in single j A=46 has a closed shell of neutrons. Most experimental measurements had the opposite --larger B(E2) for A=44 than for A=46. But a most recent measurement by Mengone et al. disagrees with all previous measurements and agrees with the current shell model calculations. [Preview Abstract] |
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