Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session E14: Few Body Problems |
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Chair: Charlotte Elster, Ohio University Room: Hyatt Regency Dallas Cumberland I |
Saturday, April 22, 2006 3:30PM - 3:42PM |
E14.00001: Influence of the N*1440 and N*1535 Resonances in Intermediate Energy pp and np Scattering Ch. Elster, A. Schwick, A. Gardestig, F. Hinterberger Recent precision measurements of pp spin correlation observables up to 2.5 GeV projectile energy rekindled interest in comparing available models of the NN interaction to those data. It is well known that the Delta resonance plays a dominant role in the energy region between pion production threshold and roughly 1 GeV, and is incorporated in all models of the NN interaction defined in this energy regime. It is natural to assume that when going higher in energy and leaving the regime of the Delta dominance, other low lying, distinct nucleon resonances may be important for a description of the data. Here we study the influence of the N*1440 (decaying mostly to N$\pi$) and the N*1535 (decaying to N$\pi$ and N$\eta$) on pp and np observables. Though the overall contributions of both N* resonances is much smaller than those of the Delta, they are quite visible in in T=0 channels close to pion threshold. A model for the NN interaction respecting unitarity and based on meson exchange and including the Delta, N*1440, and N*1535 resonances will be compared to np and pp data as well as phase-shift analyses for laboratory energies up to 1.3 GeV. [Preview Abstract] |
Saturday, April 22, 2006 3:42PM - 3:54PM |
E14.00002: Microscopic approach to scattering states in $^5$He Hartmut M. Hofmann, Gerald M. Hale In the framework of the resonating group model we study scattering states in $^5$He using realistic two- and three-nucleon forces. We allow for $\alpha$ - neutron and triton - deuteron channels with relative angular momenta up to L = 2. The coupling to the first excited state of the $\alpha$ particle is also taken into account. We compare the results of the calculations to those of a comprehensive R-matrix analysis partial wave by partial wave. The agreement for the S-waves is very good. The calculated P-wave phase shifts do not yet reach the data. Preliminary results indicate the importance of internal D-waves inside the deuteron. The D-wave results are still in progress. We discuss the effects of the NNN-force and the coupling to the $\alpha^*$ - neutron channel. [Preview Abstract] |
Saturday, April 22, 2006 3:54PM - 4:06PM |
E14.00003: Proton -- $^{3}$He Elastic Scattering at Low Energies B. M. Fisher, C. R. Brune, H. J. Karwowski, D. S. Leonard, E. J. Ludwig, T. C. Black, M. Viviani, A. Kievsky, S. Rosati We present new accurate measurements of the differential cross section $\sigma(\theta)$ and the proton analyzing power $A_{y}$ for proton--$^{3}\mathrm{He}$ elastic scattering at various energies. The $\sigma(\theta)$ distributions have been measured at $E_{\mathrm{p}}$ = 0.99, 1.59, 2.24, 3.11, and 4.02 MeV. Full angular distributions of $A_{y}(\theta)$ have been measured at $E_{\mathrm{p}}$ = 1.60, 2.25, 3.13, and 4.05 MeV. This set of high-precision data is compared to four-body variational calculations employing realistic nucleon-nucleon ($NN$) and three-nucleon ($3N$) interactions. For the unpolarized cross section the agreement between the theoretical calculation and experimental data is good when a realistic $3N$ potential is included. However, the comparison between the calculated and measured proton analyzing powers reveals discrepancies of approximately 50\% at the maximum of each distribution. [Preview Abstract] |
Saturday, April 22, 2006 4:06PM - 4:18PM |
E14.00004: Comparison of results for $N+N$ scattering at low energies G. M. Hale, C. P. Liu We show comparisons of $N+N$ scattering observables calculated from the Nijmegen potential with those obtained from an $R$-matrix analysis of low-energy measurements for the $N+N$ system. Of particular interest are the spin-dependent $S$-wave scattering lengths for $n+p$ scattering, and selected observables (with their associated uncertainties) for $n+p$ capture. We will discuss implications of the comparisons for the nature of phenomenological $N-N$ interactions. [Preview Abstract] |
Saturday, April 22, 2006 4:18PM - 4:30PM |
E14.00005: Neutron-deuteron scattering in configuration space Vladimir Suslov, Mikhail Braun, Branislav Vlahovic A new computational method for solving the configuration-space Faddeev equations for the breakup scattering problem [1] has been applied to consider \textit{nd} scattering both below and above two-body threshold. To perform numeric calculations for arbitrary nuclear potential and with arbitrary number of partial waves retained, we use approach proposed in [2]. The calculations of the inelasticity and phase-shift, as well the breakup amplitudes for \textit{nd} scattering for various lab energies were performed with the charge independent AV14 potential. The results are compared with those of Bochum and Pisa group [3]. 1. V.M. Suslov and B. Vlahovic, Phys. Rev. C \textbf{69}, 044003 (2004). 2. S.P. Merkuriev, C. Gignoux and A. Laverne, Ann. Phys. \textbf{99}, 30 (1976). 3. W. Gl\"{o}ckle, H. Witala, D. H\"{u}ber, H. Kamada, J. Golak, Physics Report, \textbf{274}, 107 (1996). [Preview Abstract] |
Saturday, April 22, 2006 4:30PM - 4:42PM |
E14.00006: Novel approach to effective interactions for many-body calculations Ionel Stetcu, Bruce R. Barrett, Ubirajara van Kolck Even in the absence of exact solutions from QCD, effective field theories (EFT) provide a modern understanding of the nuclear forces at low energies. Based on a EFT which integrates out the pions as degrees of freedom (pionless theory), we present a new approach to the derivation of effective interactions suitable for many-body calculations by means of the no-core shell model. Such an approach can provide a consistent, order-by-order improvable method to obtain interactions tailored for the model spaces used in the many-body calculations, as well as the corresponding electromagnetic and weak operators. In this work, we concentrate on the description of two-body scattering observables in a restricted harmonic oscillator basis. I.S. and B.R.B. acknowledge partial support by NSF grant numbers PHY0070858 and PHY0244389. U.v.K. acknowledges partial support from DOE grant number DE-FG02-04ER41338 and from the Sloan Foundation. [Preview Abstract] |
Saturday, April 22, 2006 4:42PM - 4:54PM |
E14.00007: Calculation of the two-body scattering T-matrix in Configuration Space George Rawitscher Three-body Faddeev calculations require as input two-body T-matrices. For atomic physics applications configuration space is preferable over momentum space, since the potentials are given in the former. A recently developed solution of the Lippmann-Schwinger integral equation for the one-variable scattering wave function in configuration space [1] has now been extended to obtain the two variable scattering T-matrix, as will be shown. The method is based on spectral expansions into Chebyshev Polynomials of two auxiliary functions in each radial partition, in terms of which the T-matrix is obtained. The result is an important ingredient for the solution of the Faddeev integral equations in configuration space [2]. \newline \newline [1] G. Rawitscher and I. Koltracht, Computing in. Sc. and Eng., 7, 58 (2005); \newline [2] W. Gl\"{o}ckle, and G. Rawitscher; ``Three-atom scattering via the Faddeev scheme in configuration space,'' submitted for publication, and physics/0512010 at arxiv.com;. [Preview Abstract] |
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