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 DB: Mini-Symposium on Confronting ab-initio Theories of Nuclear Structure and Reactions with Experiments |
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Chair: Lucas Platter, Argonne National Laboratory Room: Plaza II |
Thursday, October 25, 2012 10:30AM - 11:06AM |
DB.00001: \textit{Ab initio} theories of nuclear structure and reactions Invited Speaker: Petr Navratil The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces with two-nucleon, three-nucleon and possibly even four-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in \textit{ab initio} nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. I will discuss recent breakthroughs that allow for \textit{ab} \textit{initio} calculations for ground states and spectroscopy of nuclei throughout the $p$- and \textit{sd}-shell and beyond with two- and three-nucleon interactions. I will highlight results obtained within the NCSM, CCM, QMC, and nuclear lattice EFT. I will also present new \textit{ab initio} many-body approaches capable of describing both bound and scattering states in light nuclei simultaneously and discuss results for reactions important for astrophysics, such as $^{7}$Be(p,$\gamma )^{8}$B radiative capture, and for $^{3}$H(d,n)$^{4}$He fusion. [Preview Abstract] |
Thursday, October 25, 2012 11:06AM - 11:18AM |
DB.00002: The Gamow Shell Model as a tool for ab-initio nuclear structure calculations George Papadimitriou, Bruce Barrett, Jimmy Rotureau, Marek Ploszajczak No core Gamow shell model (NCGSM) is applied for the first time to study selected well-bound and unbound states of helium isotopes. This model, formulated in the rigged Hilbert space and using a complete Berggren ensemble, is appropriate for a description of bound states, resonances, and the many-body scattering states. The ``dimensional catastrophe'' in NCGSM when increasing the number of active particles is much more serious than in the No Core Shell Model (NCSM). This problem has been alleviated by the application of the Density Matrix Renormalization Group (DMRG) method, opening a possibility for the \textit{ab initio} calculation of exotic states in hydrogen, helium and lithium chains of isotopes. The \textit{ab initio} NCGSM calculations start from either bare interaction or various renormalized two-body interactions such as Vlow-k. The single-particle Berggren ensemble consisting of bound, resonance and non-resonant continuum states is generated by the corresponding Gamow-Hartree-Fock potential. To test the validity of our approach, we benchmarked the NCGSM results against Fadeev and Fadeev-Yakubovsky exact calculations for $^{3}$H and $^{4}$He nuclei. We also performed \textit{ab-initio} NCGSM calculations for the unstable nucleus $^{5}$He and determined the ground state energy and decay width, starting from a realistic N$^{3}$LO interaction. [Preview Abstract] |
Thursday, October 25, 2012 11:18AM - 11:30AM |
DB.00003: Some recent developments in the description of light-nuclei reactions within the NCSM/RGM approach G. Hupin, J. Langhammer, C. Romero-Redondo, P. Navratil, R. Roth, S. Quaglioni The fundamental description of both structural properties and reactions of light-nuclei based on nucleon-nucleon and three-nucleon forces derived from first principles is a standing goal in nuclear physics. The {\it ab initio} no-core shell model when combined with the resonating-group method (NCSM/RGM) [1,2] is capable of describing simultaneously both bound and scattering states in light nuclei, and has already produced promising results starting from a two-body Hamiltonian. Using similarity-renormalization-group evolved two- and three-nucleon interactions [3,4], I will present the first applications to light nuclei binary scattering processes when accounting for the chiral two- plus three-nucleon interaction versus the chiral two-nucleon interaction. Finally, I will outline the progress toward the treatment of three-body clusters within our formalism.\\ \,[1] S. Quaglioni and P. Navr\'atil, PRL {\bf 101}, 092501 (2008); PRC {\bf 79}, 044606 (2009). [2] P. Navr\'atil and S. Quaglioni, PRC {\bf 83}, 044609 (2011). [3] E. Jurgenson, P. Navr\'atil and R. J. Furnstahl, PRC {\bf 83}, 034301 (2011). [4] R. Roth, J. Langhammer, A. Calci, S. Binder, and P. Navr\'atil, PRL {\bf 107}, 072501 (2011). [Preview Abstract] |
Thursday, October 25, 2012 11:30AM - 11:42AM |
DB.00004: Stucture of $^9$C from the d($^{10}$C,\textit{t})$^{9}$C Reaction and the Reliability of Ab Initio Transfer Form Factors S.T. Marley, A.H. Wuosmaa, S. Bedoor, J.C. Lighthall, D.V. Shetty, M. Alcorta, P.F. Bertone, J.A. Clark, C.L. Jiang, T. Palchan-Hazan, R.C. Pardo, K.E. Rehm, A.M. Rogers, R.B. Wiringa, C.M. Deibel, C. Ugalde A paucity of information exists on the structure of the neutron-deficient nucleus $^{9}$C which is accessible to \emph{ab-initio} calculations such as the Quantum Monte Carlo approach. In addition to excitation energies in the A=9 \& 10 systems, it is possible to calculate the spectroscopic overlaps relevant for the neutron-pickup reaction \emph{d}($^{10}$C,\emph{t})$^{9}$C. To test these predictions of the neutron-pickup spectroscopic factors, we have studied the $^{10}$C(\emph{d},\emph{t})$^9$C reaction, in inverse kinematics. A 171-MeV $^{10}$C beam was produced at the ATLAS In-Flight Facility with an intensity of 2$\times$10$^4$ pps and was incident on a deuterated polyethylene [CD$_{2}$]$_{n}$ target. The ground-state transition was clearly observed in a series of silicon detector arrays and angular-distribution data were extracted. The neutron-pickup spectroscopic factor was deduced from a comparison with distorted-wave calculations, with both traditional and QMC-derived bound-state form factors. A comparison between the results of these methods will be presented. [Preview Abstract] |
Thursday, October 25, 2012 11:42AM - 11:54AM |
DB.00005: Evidence for three nucleon interactions in light nuclei James Vary, Pieter Maris Refining our experimental and theoretical knowledge of three-nucleon interactions is a necessary pre-requisite for isolating possible signatures of four-nucleon interactions. We review the accumulated results indicating where signatures of three-nucleon interactions are now established in light nuclei. We especially focus on selected electroweak transitions such as the strongly suppressed Gamow-Teller transition in Carbon-14 and the enhanced B(M1) transition to the 1+1 state in Carbon-12. Overall binding energies and selected spectral properties show additional effects of three-nucleon interactions. Since many nuclear properties appear rather insensitive to three-nucleon interaction effects, it will take a concerted effort of theorists and experimentalists to define observables that both carry sensitivity to three-nucleon interactions and that are experimentally accessible. This community effort should involve a variety of ab initio many-body approaches as well as the available candidate three-nucleon interactions. It should consider a wide scope of experimental opportunities. High precision theory and experiment can combine to maximize our gain in knowledge with leadership class computational facilities and next-generation experimental facilities such as FRIB. [Preview Abstract] |
Thursday, October 25, 2012 11:54AM - 12:06PM |
DB.00006: Nuclear structure from lattice effective field theory Dean Lee Effective field theory provides a systematic approach to interacting quantum systems at low energies and densities. Lattice effective field theory combines this approach with non-perturbative lattice methods. I discuss recent applications of lattice effective field theory to nuclear structure. I also discuss new developments and ideas in the field. [Preview Abstract] |
Thursday, October 25, 2012 12:06PM - 12:18PM |
DB.00007: Ab initio many-body calculations of the $^4$He photo-absorption cross section Micah Schuster, Sofia Quaglioni, Calvin Johnson, Eric Jurgenson, Petr Navr\'{a}til Using the no-core shell model approach with a similarity renormalization group (SRG) evolved two- and three-nucleon (NN+NNN) Hamiltonian, we compute the dipole strength function of $^4$He, using the Lorentz integral transform (LIT) method to obtain the continuum response. We then compute the total photo-absorption cross section of $^4$He. We pay particular attention to the convergence of the total strength and of the LIT of the dipole response as we increase the size of the harmonic oscillator basis. [Preview Abstract] |
Thursday, October 25, 2012 12:18PM - 12:30PM |
DB.00008: Uncertainty quantification in the Importance-truncated No-Core Shell Model Michael Kruse, Eric Jurgenson, Petr Navratil, Bruce Barrett, Erich Ormand The No-Core Shell Model (NCSM) is a first-principles nuclear structure technique with which one can calculate the observable properties of light nuclei (A $<$ 20). Unfortunately, the many-body basis space size required for convergence of the ground-state energy is often on the order of a billion states; too large for most computer-codes in use today. The Importance-truncated NCSM, IT-NCSM, formulated on arguments of multi-configurational perturbation theory selects a small set of basis states from the initially large NCSM basis space in which the Hamiltonian is now diagonalized. Previous IT-NCSM calculations have proven reliable, however, there has been no thorough investigation of the inherent error in the truncated IT-NCSM calculations. We provide a detailed study of IT-NCSM calculations using Li-6 as our test case. Our analysis includes a study of IT-NCSM ``errors'' as a function of the size of the basis, the harmonic oscillator energy, as well as the extrapolation functions used. [Preview Abstract] |
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