Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session MC: Mini-symposium on Reaction Theory for FRIB I |
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Chair: Akram Mukhamedzhanov, Texas A&M University Room: Sweeny C |
Saturday, November 6, 2010 8:30AM - 9:06AM |
MC.00001: Nuclear Reactions -- a Challenge for Few- and Many-Body Theory Invited Speaker: It is a particular exciting time for rare isotope science. As the engineering and construction issues for the new facility for rare isotopes (FRIB) are tackled, the physics community prepares to address the challenging science. A large fraction of the FRIB program will involve direct reactions with rare isotope beams, reactions, which leave a good part of the beam nuclei intact. Thus, the theory of nuclear reactions is central to understanding experiments at FRIB. The reliable prediction of reactions with rare isotopes will be major piece in the theory effort for FRIB. Over the last decade tremendous progress has been in made in exact descriptions of nuclear few-body systems as well as in nuclear structure calculations. The expertise gained in both of these areas will be essential to face the challenge in describing nuclear reactions with rare isotopes. This presentation will use a few examples to illustrate, where the synergy of few- and many-body theory will be able to address the challenges nuclear reactions with rare isotopes faces. [Preview Abstract] |
Saturday, November 6, 2010 9:06AM - 9:18AM |
MC.00002: MCNP6 -- A New Simulation Tool for FRIB Applications Stepan Mashnik During the last decade, we have developed at LANL improved codes of the Cascade-Exciton Model (CEM) and of the Los Alamos version of the Quark-Gluon String Model (LAQGSM) to describe reactions induced by particles and nuclei. We have tested our CEM and LAQGSM codes against a large variety of experimental data on particle-particle, particle-nucleus, and nucleus-nucleus reactions and have compared their results with predictions by other models. The latest versions of our codes, CEM03.02 and LAQGSM03.03, have been incorporated recently as event generators in MCNP6, the latest and most advanced LANL transport code representing a merger of MCNP5 and MCNPX, which can be a useful tool for FRIB simulations. Here, we present a brief description of CEM03.02 and LAQGSM03.03 and several illustrative results by MCNP6 with our event generators for both thin and thick targets of interest to FRIB. [Preview Abstract] |
Saturday, November 6, 2010 9:18AM - 9:30AM |
MC.00003: Non-local Optical Potentials Ian Thompson In all direct reactions to probe the structure of exotic nuclei at FRIB, optical potentials will be needed in the entrance and exit channels. At high energies Glauber approximations may be useful, but a low energies (5 to 20 MeV/nucleon) other approaches are required. Recent work of the UNEDF project [1] has shown that reaction cross sections at these energies can be accounted for by calculating all inelastic and transfer channels reachable by one particle-hole transitions from the elastic channel. In this model space, we may also calculate the two-step dynamic polarization potential (DPP) that adds to the bare folded potential to form the complex optical potential. Our calculations of the DPP, however, show that its non-localities are very significant, as well as the partial-wave dependence of both its real and imaginary components. The Perey factors (the wave function ratio to that from an equivalent local potential) are more than 20\% different from unity, especially for partial waves inside grazing. These factors combine to suggest a reexamination of the validity of local and L-independent fitted optical potentials, especially for capture reactions that are dominated by low partial waves. Prepared by LLNL under Contract DE-AC52-07NA27344. [1] G.P.A. Nobre, F.S. Dietrich, J.E. Escher, I.J. Thompson, M. Dupuis, J. Terasaki and J. Engel, submitted to Phys. Rev. Letts., 2010. [Preview Abstract] |
Saturday, November 6, 2010 9:30AM - 9:42AM |
MC.00004: Towards quantum transport for central nuclear reactions Brent W. Barker, Arnau Rios, Pawel Danielewicz Efforts are on the way to develop a practical non-equilibrium Green's functions approach to central nuclear reactions. With the goal of reducing the computational space, the importance of the far off-diagonal elements in the spatial density matrix is investigated for one-dimensional slab collisions following the mean-field approximation. A truncation of these far off-diagonal elements has no effect on the evolution of the system close to the diagonal of the density matrix, though the time-reversed evolution is affected at a significant level. Further, the truncation softens interference effects present in the Wigner distribution for the collisions. Beyond the mean-field approximation, preliminary results for the inclusion of correlations are also presented. [Preview Abstract] |
Saturday, November 6, 2010 9:42AM - 9:54AM |
MC.00005: GFMC calculations of one-nucleon overlaps and spectroscopic factors in light nuclei Ivan Brida, Steven C. Pieper, R.B. Wiringa We present one-nucleon overlap functions for light $(A \le 10)$ nuclei computed from ab-initio Green's function Monte Carlo wave functions. The wave functions are based on realistic two- and three-nucleon Av18+IL7 interactions. Our overlap functions extend into long-range regions with correct asymptotics. The overlap functions are used to obtain spectroscopic factors and can serve as an input for low-energy reaction calculations. [Preview Abstract] |
Saturday, November 6, 2010 9:54AM - 10:06AM |
MC.00006: A Nucleon-Nucleus Optical Potential for Rare Isotope Beam Facilities Stephen Weppner A global nucleon-nucleus optical potential for elastic scattering has been produced\footnote{Weppner et. al.; Phys. Rev. C 80, 034608 (2009)} which replicates experimental data to high accuracy and compares well with other recently formulated global optical potentials. The calculation that has been developed describes proton and neutron scattering from target nuclei ranging from carbon to nickel and is applicable for projectile energies from 30 MeV to 160 MeV. With these ranges it is suitable for calculations associated with recent and future experiments performed by rare isotope beam accelerators. Elastic cross section and spin observables from this phenemological potential will be compared to other optical potentials results and experimental data. Deficiencies in the theoretical models and experimental reaction database will be discussed. [Preview Abstract] |
Saturday, November 6, 2010 10:06AM - 10:18AM |
MC.00007: Asymptotic normalizations and related quantities from quantum Monte Carlo wave functions Kenneth Nollett Asymptotic normalization coefficients (ANCs) are amplitudes of nuclear overlap functions at large radius. As such, they characterize several properties of bound nuclei including amplitudes of transfer reactions. In both variational and basis methods, accurate ANCs are difficult to extract directly from overlaps. However, they may also be obtained by a Green's-fuction approach that yields ANCs as integrals over the better-determined short-range parts of the wave functions. I will describe the application of this integral approach to {\it ab initio} wave functions computed by the variational Monte Carlo and Green's function Monte Carlo methods, and I will present results for $A\leq 10$. Surface amplitudes of unbound states may be found by essentially the same method, yielding scattering and reaction amplitudes and resonance widths. As an illustration of the method, I will discuss the problem of properly normalizing parity-violating matrix elements in neutron-$^4$He scattering. [Preview Abstract] |
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