Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session HF: Reactions: FewN/ Light Systems 
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Chair: Rocco Schiavella, Thomas Jefferson National Accelerator Facility Room: Blue Point II 
Friday, October 25, 2013 8:30AM  8:42AM 
HF.00001: Update on the direct nn scattering experiment at the reactor YAGUAR S.L. Stephenson, B.E. Crawford, W.I. Furman, E.V. Lychagin, A. Yu. Muzichka, G.V. Nekhaev, E.I. Sharapov, V.N. Shvetsov, A.V. Strelkov, B.G. Levakov, A.E. Lyzhin, Yu. I. Chernukhin, C.R. Howell, G.E. Mitchell, W. Tornow, R.A. ShowalterBucher The first direct measurement of the $^{1}S_{0}$ neutronneutron scattering experiment using the YAGUAR aperiodic reactor at the Russian Federal Nuclear Center $$ All Russian Research Institute of Technical Physics has preliminary results. Thermal neutrons are scattered from a thermal neutron ``gas'' within the scattering chamber of the reactor and measured via timeofflight. These initial results show an unexpectedly large thermal neutron background now understood to be from radiationinduced desorption within the scattering chamber. Analysis of the neutron timeofflight spectra suggests neutron scattering from H$_2$ and possibly H$_2$O molecules. An experimental value for the desorption yield $\eta_{\gamma}$ of 0.02 molecules/gamma agrees with modeled results. Techniques to reduce the effect of the nonthermal desorption will be presented. [Preview Abstract] 

HF.00002: ABSTRACT WITHDRAWN 
Friday, October 25, 2013 8:54AM  9:06AM 
HF.00003: Photoproduction of $\Lambda $(1115) on a deuteron at threshold energies Brian Beckford The electromagnetic production of strange mesons and baryons continues to be a growing topic in more recent years due in part to the continual increase of beam energies at accelerator facilities. It is well known that production of strangeness on nucleons provides details about hadronic structures including form factors. We present results on cross sections for $\Lambda$ in the $\gamma $d$\to \Lambda $X reaction measured at the Research Center for Electron Photon Science (ELPH), at tagged photon energies between 0.81.08 GeV. The experiment was successfully performed using the upgraded Neutral Kaon Spectrometer (NKS2$+)$ where the produced $\Lambda $ was measured by the p$\pi^{}$ decay channel. Momentum and angular distributions were measured in addition to the integrated cross section for forward $\Lambda $ scattering angles. From integrated measurements of $\Lambda $ from $\gamma $d$\to \Lambda $X, total cross sections of $\gamma $d$\to $K$^{0}\Lambda $p were estimated. The results of the SaclayLyon A (SLA) [1] and ReggePlusResonance (RPR2007) model [2] calculations compared favorably to the data.\\[4pt] [1] T. Mizutani, C. Fayard, G. H. Lamot, and B. Saghai. Phys Rev. C 58,75 (1998).\\[0pt] [2] P. Vancraeyveld et.al. Nucl. Phys. A 897,42 (2013). [Preview Abstract] 
Friday, October 25, 2013 9:06AM  9:18AM 
HF.00004: Test of the slow variable discretization method in the adiabatic hyperspherical treatment of the $p+n+n$ system Kevin Daily, Chris Greene, Alejandro Kievsky We consider the $p+n+n$ system using the Argonne $v_{18}$ plus the Urbana IX threenucleon potential in the adiabatic hyperspherical description. Considering the $J=1/2+$ state, we solve for bound states and scattering properties in a twostep method. First, we use a hyperspherical harmonic expansion to calculate the adiabatic potential curves as a function of the hyperradius $R$. Second, we solve the remaining set of coupled equations in $R$ using GaussLobatto basis function in a discrete variable representation together with a slow variable discretization of $R$ [O.~I. Tolstikhin, S. Watanabe, and M. Matsuzawa, J. Phys. B {\bf 29} L389 (1996)]. The resulting bound state energies not only agree well with benchmark calculations, but also show favorable convergence properties in comparison with the direct calculation of the coupling matrices. Two and threebody scattering properties of the system are also calculated and extension to other scattering states and to the fournucleon problem are discussed. [Preview Abstract] 
Friday, October 25, 2013 9:18AM  9:30AM 
HF.00005: Ratios of hadronic continuum spectra to deuterium R.J. Peterson The role of shortrange correlations among nucleons in complex nuclei was recently demonstrated with 5.766 GeV electrons by plotting ratios of inclusive doublydifferential cross sections from nuclei to the same for deuterium, with a sharp rise noted for Bjorken x \textgreater\ 1 [N. Fomin et al. Phys. Rev. Lett. \textbf{108}, 092502(2012)]. A similar set of data for scattering of hadrons, both with and without charge exchange, has been put into such ratio form for lower beam energies and momentum transfers q. For q near 500 MeV/c the data ratios rise with x for several nuclei and beams, but less strongly than the recent electron data. When a large range of hadronic ratios to deuterium are plotted on a length scale set by 1/Q, the fourmomentum transfer, a smooth trend is found, joining the electron ratio data at large Q. [Preview Abstract] 
Friday, October 25, 2013 9:30AM  9:42AM 
HF.00006: Measurement of the $^{3}{\rm H}(d,\gamma)$/$^{3}{\rm H}(d,n)$ Branching Ratio at CenterofMass Energies Below 300~keV Cody Parker, Carl Brune, Thomas Massey, Daniel Sayre, John O'Donnell The branching ratio $^{3}{\rm H}(d,\gamma)^{5}{\rm He}$/$^{3}{\rm H}(d,n)\alpha$ has been measured using a 500keV pulsed deuteron beam incident on a stopping titanium tritide target at the Edwards Accelerator Laboratory. The timeofflight technique has been used to distinguish the $\gamma$rays from the neutrons in the bismuth germinate $\gamma$ray detector. Two stilbene scintillators and an NE213 scintillator have been used to detect the neutrons using both the pulseshape discrimination and timeofflight techniques. The preliminary measurement at a crosssectionweighted average energy of 196 keV that produced a branching ratio measurement of (6.9$\pm$1.6)$\times$10$^{5}$ and plans for future measurements will be presented. [Preview Abstract] 
Friday, October 25, 2013 9:42AM  9:54AM 
HF.00007: $R$Matrix Analysis of Particle Spectra from the T(t,2n)$\alpha$ Reaction at Low Energies Carl R. Brune, Joseph A. Caggiano, Daniel B. Sayre, Gerald M. Hale, Mark W. Paris The particle spectra from the lowenergy T(t,2n)$\alpha$ reaction are of interest to several research areas, including fusion energy and the neutronneutron scattering length. We present an $R$Matrix model for the final states of this reaction, considering sequential neutron emission via $l=0$ and 1 $n+\alpha$ intermediate states as well as emission of a correlated $l=0$ $n+n$ (dineutron) pair. The amplitudes for these processes are constructed to be antisymmetric under neutron exchange. The twobody $n+\alpha$ channel is highly constrained by existing experimental data. Substantial effects in the neutron and $\alpha$particle energy spectra are found to result from antisymmetrization as well as from the interference between different decay channels. Results for fits to the available experimental data will be presented. [Preview Abstract] 
Friday, October 25, 2013 9:54AM  10:06AM 
HF.00008: Marrying {\it ab initio} calculations and HaloEFT: $^{7}$Li and $^{7}$Be radiative nucleon captures Xilin Zhang, Kenneth Nollett, Daniel Phillips We combine {\it ab initio} quantumMonteCarlo (QMC) calculations with the HaloEffectiveFieldTheory (HaloEFT) framework, in order to study lowenergy radiative nucleon capture to a weakly bound (halo) nucleus. Here we focus on the reactions $^{7}$Li(n,$\gamma$)$^{8}$Li and $^{7}$Be(p,$\gamma$)$^{8}$B, which are subjects of longstanding interest for astrophysics. In the lowenergy region we can approximate $^{8}$Li ($^{8}$B) as composed of a $^{7}$Li ($^{7}$Be) core (and also its excitation), and a neutron (proton) with an anomalously extended wave function. The scattering and bound states can be studied in HaloEFT, in which both core and the nucleon are treated as fundamental degrees of freedom. In our leading order calculation, we use asymptotic normalization coefficients from QMC calculations to fix the parameters in the Lagrangian, which we then apply to study radiative captures. This obviates computing the captures by directly using numerically intensive QMC methods, while still incorporating the nuclear dynamics that these methods provide. In addition, the modelindependent EFT framework provides novel insights into the manner in which these two nucleoncapture processes are related to one another. [Preview Abstract] 
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