Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session G3: Few Body Physics II |
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Sponsoring Units: DNP GFB Chair: Ronald Gilman, Rutgers University Room: Plaza E |
Sunday, May 3, 2009 8:30AM - 9:06AM |
G3.00001: JLab Few Body Form Factor Measurements Invited Speaker: A review of the few-body form factors will be presented, along with Jefferson Lab preliminary results on high momentum transfer measurements of elastic electron scattering off helium isotopes. The experimental results will be compared to predictions of meson-nucleon calculations based on the impulse approximation with inclusion of meson-exchange currents, and on quark dimensional scaling. [Preview Abstract] |
Sunday, May 3, 2009 9:06AM - 9:42AM |
G3.00002: From Deuterium to Free Neutrons - Recent Experimental Results Invited Speaker: Lepton scattering has long been used to gather data on the internal structure of both protons and neutrons. Assuming isospin symmetry, these data can be used to pin down the contributions of both $u$ and $d$ quarks to the spatial and momentum-spin structure of the nucleon and its excitations. In this context, information on the neutron is crucial and is typically obtained from experiments on few-body nuclear targets (predominantly $^{3}$He and deuterium). However, the need to account for binding effects complicates the interpretation of these experiments. On the other hand, detailed studies of the reaction mechanism can yield important new information on the structure of few-body nuclei and the interplay of nuclear and quark degrees of freedom. Recent theoretical and experimental advances have allowed us to make significant progress on both fronts -- a cleaner extraction of neutron properties from nuclear data and a better understanding of nuclear modifications of the bound neutron structure. I will concentrate on recent results on the deuteron. I will present a new extraction of neutron spin structure functions in the resonance and large-$x$ region (from the EG1 experiment with CLAS at Jefferson Lab). The same data can also be used for a detailed comparison with modern calculations of quasi-elastic spin-dependent scattering on the deuteron. A second experimental program with CLAS uses the technique of ``spectator tagging'' to extract the unpolarized structure functions of the neutron with minimal uncertainties from nuclear effects. By mapping out the dependence of the cross section on the ``spectator'' momentum, we can learn about final state interactions between the struck nucleon and the spectator, as well as modifications of the neutron structure due to nuclear binding. I will present preliminary results from the ``BoNuS'' experiment which pushed the detection limit of the spectator proton down to momenta of 70 MeV/c, where nuclear corrections should become small. [Preview Abstract] |
Sunday, May 3, 2009 9:42AM - 10:18AM |
G3.00003: Finite Range Effects in Atomic and Nuclear Three-Body Physics Invited Speaker: I examine effects of the finite range of the 2-body interaction on 3-body physics in the low energy limit where there has been much recent effort in understanding these phenomena using Effective Theories (ET's). I assume separable (SP) 2-body interactions -- widely used in nuclear 3-body calculations shortly after the crucial work of Faddeev fifty years ago -- which permit analytic solutions for the exact t-matrix which, eg, respect unitarity exactly. I compare these results with ``standard'' ET calculations in which incorporation of finite range effects is based on the Effective Range Expansion (ERE) of the 2-body on-shell scattering amplitude. We find that ET-ERE calculations for the quartet (spin=3/2) s-wave channel of neutron-deuteron elastic scattering disagree significantly from the the SP results in some cases. I discuss the origin and the significance of these discrepancies. I also discuss similar sets of calculations for cold, dilute atomic Bose gases. These provide a relatively simple means of reliably computing, eg, 3-body recombination coefficients while appropriately accounting for Efimov physics. I also discuss how these calculations can be adapted to treat certain many-body effects in Bose gases which might help in understanding, eg, the single quasi-particle dispersion relation as revealed by Bragg scattering experiments. [Preview Abstract] |
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