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 D4: Few Body Nuclear Physics II |
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Sponsoring Units: DNP GFB Chair: Wayne Polyzou, University of Iowa Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade B |
Saturday, April 12, 2008 1:30PM - 2:06PM |
D4.00001: The Three-Nucleon Analyzing Power Puzzle - The Past 20 Years Invited Speaker: The three-nucleon (3N) analyzing power A$_{y}$($\theta$) puzzle (3NAPP) refers to the failure of rigorous 3N calculations to account for the magnitude of the measured nucleon-deuteron A$_ {y}$($\theta$) in the angular region of the A$_{y}$ maximum (~30\% underprediction). The 3NAPP is a low-energy phenomenon and does not refer to A$_{y}$($\theta$) in the energy range above 100 MeV, where standard 3N forces contribute significantly to A$_{y}$($\theta$) in the angular region of the cross-section minimum. The 3NAPP was discovered by Wita{\l}a, Gl\"{o}ckle and Cornelius in 1987 when they compared their rigorous 3N calculations to the neutron-deuteron (n-d) data of the T\"{u}bingen/TUNL group, although some evidence of a possible problem with describing A$_{y}$($\theta$) was already reported in 1986 by Koike and Haidenbauer. Before 1995 the 3NAPP was solely a n-d scattering phenomenon. However, with the Coulomb problem solved in 3N calculations by Kievsky, Viviani and Rosati in 1995 for energies below, and in 1999 for energies above the deuteron breakup threshold, the 3NAPP entered a new stage and included A$_{y}$($\theta$) in proton-deuteron (p-d) scattering as well as the vector analyzing power iT$_{11} $($\theta$) in d-p scattering. Although p-d phase-shift analyses and their comparison to theoretical phase shifts provided some insight into the physics of the 3NAPP, the accurate p-d data initially created a new problem at energies below about 5 MeV, until the theoretical treatment of the magnetic moment interaction by Wita{\l}a et al. and Kievsky et al. provided a uniform picture. The recent inclusion of relativity in 3N calculations by Wita{\l}a et al. has increased the 3NAPP at low energies considerably (by about 25\% at 5 MeV). Furthermore, the new n-d A$_{y}$($\theta$) data obtained by Weisel et al. at TUNL confirmed our conjecture that the transition region between 20 MeV and about 35 MeV, above which the 3NAPP disappears, is poorly understood. Here, p-d data are needed to make progress. Currently, the hope is that the 3N force terms predicted by Chiral Effective Filed Theory in N3LO will eventually provide the correct explanation of the 3NAPP. However, the range of the required 3N force terms has to be about 3 fm in order to describe the A$_{y}$($\theta$) and iT$_{11}$($\theta$) data at E$_ {c.m.}$=432 keV. [Preview Abstract] |
Saturday, April 12, 2008 2:06PM - 2:42PM |
D4.00002: Towards a Microscopic Density Functional Theory for Nuclei Invited Speaker: Density functional theory (DFT) has enjoyed spectacular success describing inhomogeneous many-electron systems in condensed matter physics and chemistry where \textit{ab initio} methods become computationally prohibitive, as was recognized by the Nobel Prize awarded to Walter Kohn in 1998. Because of the computational limitations of \textit{ab initio} methods in medium and heavy nuclei, DFT is the only tractable many-body method that can at present be applied across the entire table of nuclides. Remarkably simple phenomenological functionals of the Skyrme and Gogny type have enjoyed nearly four decades of impressive success describing a wide range of nuclear properties for many different mass regions. However, different parameterizations lead to uncontrolled (i.e., parameterization-dependent) extrapolations far from stability, with no reliable method to estimate the theoretical error bars. A primary objective of the SciDAC project ``Building a Universal Nuclear Energy Density Functional (UNEDF)'' is to develop a \textit{microscopically-based}, energy density functional applicable to all nuclei in the form of a generalized Skyrme functional, with theoretical error bars for the different terms in the UNEDF to provide guidance for fine-tuning to data and to give controlled extrapolations away from stability. In this talk, I describe a promising route for achieving these objectives that combine recent advances in chiral effective field theory (EFT) inter-nucleon interactions, renormalization group (RG) techniques for nuclear systems, and nuclear many-body computational methods. [Preview Abstract] |
Saturday, April 12, 2008 2:42PM - 3:18PM |
D4.00003: {\it Ab initio} no-core shell model with continuum Invited Speaker: The {\it ab initio} no-core shell model (NCSM) is a many-body approach to nuclear structure of light nuclei. The NCSM adopts an effective interaction theory to transform fundamental inter-nucleon interactions into effective interactions for a specified nucleus in a selected harmonic oscillator basis space [1]. The method is capable of predicting nuclear structure from inter-nucleon forces derived from quantum chromodynamics by means of chiral effective field theory [2]. NCSM extensions to the microscopic description of nuclear reactions are now under development. In my talk, I will first discuss our recent calculations of the $^4$He total photo-absorption cross section using two- and three-nucleon interactions from chiral effective field theory [3]. I will then outline our effort to augment the NCSM by the resonating group method (RGM) technique to develop a new method capable of describing simultaneously both bound states and nuclear reactions on light nuclei [4]. This approach, which preserves translational symmetry and the Pauli principle, will allow us to calculate cross sections of reactions important for astrophysics and describe weakly-bound systems from first principles. I will present our first phase shift results for neutron scattering off $^3$H, $^4$He and $^7$Li and proton scattering off $^3$He, $^4$He and $^7$Be using realistic nucleon-nucleon potentials. \vspace{3mm} \newline[1] P. Navr\'atil, J. P. Vary and B. R. Barrett, Phys. Rev. C {\bf 62}, 054311 (2000). \newline[2] P. Navr\'atil and V. G. Gueorguiev and J. P. Vary, W. E. Ormand and A. Nogga, Phys. Rev. Lett. {\bf 99}, 042501 (2007). \newline[3] S. Quaglioni and P. Navr\'atil, Phys. Lett. B {\bf 652}, 370 (2007). \newline[4] S. Quaglioni and P. Navr\'atil, arXiv:0712.0855. [Preview Abstract] |
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