Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session E5: Nuclear Structure I |
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Sponsoring Units: DNP Chair: Con Beausang, University of Richmond Room: Key 1 |
Saturday, April 11, 2015 3:30PM - 3:42PM |
E5.00001: The Quasi-Electron Shell Structure of the Fractional Quantum Hall Effect Wick Haxton, Daniel Haxton The fractional quantum Hall effect (FQHE) formulated on a sphere resembles the nuclear shell model, with the desired translationally invariant states having total angular momentum zero. This property was exploited by Ginocchio and Haxton (GH) to derive a new set of scalar operators and a first-Landau-level representation of the full set of hierarchy states (fillings 1/3, 2/5, 3/7, etc.), with overlaps identical to those of Jain, who used unphysical higher Landau levels excitations followed by numerical projection. We demonstrate that the GH operators produce an appealing description of the FQHE as shells filled by non-interacting quasi-electrons, or composite fermions. These are explicitly constructed, and their planar forms are also found. The evolution of the shells and their quasi-electrons is quite unusual. The connections with electron correlations and Laughlin's variational arguments are described. We discuss how ``new states'' found experimentally at fillings such as 4/11 and 5/13 fit into this scheme. [Preview Abstract] |
Saturday, April 11, 2015 3:42PM - 3:54PM |
E5.00002: Studying the Delta-Delta component in the Deuteron Shankar Adhikari, Misak Sargsian The Delta-Delta component is expected to be one of the largest non-nucleonic components in the high momenta part of the deuteron wave function. It's magnitude will reveal indirectly the extend of the hidden-color in the deuteron as well as the dynamics relevant to the repulsive core of the NN interaction. To describe this component we developed a theoretical model based on the light-cone perturbation theory in which the Delta-Delta state is due to highly virtual NN-> Delta Delta transition in the intermediate state. Calculation is based on the collinear approximation in which the initial NN state is described by light-cone pn deuteron wave function and the NN-> Delta Delta transition amplitude is parameterized from the experiment with off-shell extrapolation. The model allowed us to calculate the total normalization of the Delta-Delta component as well as predict its momentum distribution. We then demonstrate how this component can be probed in deep-inelastic scattering off the deuteron tagged by fast backward Deltas or in high momentum transfer exclusive reactions that can identify two Delta Isobars in the final state. [Preview Abstract] |
Saturday, April 11, 2015 3:54PM - 4:06PM |
E5.00003: Deuteron Momentum Distributions at Large Momentum Transfers Werner Boeglin The exclusive deuteron electro-disintegration was studied at four-momentum transfers of 0.8, 2.1 and 3.5 GeV/c$^2$ and for missing momenta up to 600 MeV/c. Reduced cross sections as a function of missing momenta were determined for several fixed neutron recoil angles. This new, extensive data set makes it possible to identify kinematic regions where final state interactions are small and the d(e,e$'$p)n cross section is closely related to the underlying high momentum structure of the deuteron. Experimental momentum distributions for different recoil angles and momentum transfers will be presented and compared to modern calculations. [Preview Abstract] |
Saturday, April 11, 2015 4:06PM - 4:18PM |
E5.00004: The $^{3}{\rm H}(d,\gamma)$ Reaction at $E_{\rm c.m.}\leq300$~keV C.E. Parker, C.R. Brune, T.N. Massey, J.E. O'Donnell, A.L. Richard, D.B. Sayre The $^{3}{\rm H}(d,\gamma)^{5}{\rm He}$ reaction has been measured using a 500-keV pulsed deuteron beam incident on a stopping titanium tritide target at the Edwards Accelerator Laboratory. The time-of-flight technique has been used to distinguish the $\gamma$-rays from neutrons in the bismuth germinate (BGO) $\gamma$-ray detector. A stilbene scintillator and an NE-213 scintillator have been used to detect the neutrons from the $^{3}{\rm H}(d,n)\alpha$ reaction using both the pulse-shape discrimination and time-of-flight techniques. A newly designed target holder with a silicon surface barrier detector to simultaneously measure $\alpha$-particles to normalize the number of neutrons, along with a new titanium tritide target, was incorporated for subsequent measurements. The $\gamma$-rays have been measured at laboratory angles of 0~$^{\circ}$, 45~$^{\circ}$, 90~$^{\circ}$, and 135~$^{\circ}$. Information about the $\gamma$-ray energy distribution for the unbound ground state and first excited state of $^{5}{\rm He}$ can be obtained experimentally by comparing the BGO data to Monte Carlo simulations. The $^{3}{\rm H}(d,\gamma)$/$^{3}{\rm H}(d,n)$ branching ratio has also been measured. Data analysis is currently underway for the subsequent measurements. [Preview Abstract] |
Saturday, April 11, 2015 4:18PM - 4:30PM |
E5.00005: Hard Photodisintegration of $^3He$ into pd pair Dhiraj Maheswari, Misak Sargsian In this work, we study the large angle hard photodisintegration of $^3He$ nucleus into proton and deuteron pair based on the framework of Hard Rescattering Model, using photons of high energies, ranging upto 15 $GeV$. In the Hard Rescattering Model, a quark of one nucleon knocked out by an energetic incoming photon, rescatters with a quark of the other nucleon leading to the production of a proton and deuteron pair with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the model allows to write the amplitude of the break-up reaction through the convolution of photon-quark scattering, $pd \rightarrow pd$ hard scattering amplitude and nuclear spectral function which can be calculated using a nonrelativistic $^3He$ wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime. For $pd \rightarrow pd$ scattering, we use the fit of the available experimental data. One of the interesting predictions of the Hard Rescattering Model is that it tells us how the differential cross section scales with energy at large center of mass angles. For this particular case, it scales like $s^{-17}$. [Preview Abstract] |
Saturday, April 11, 2015 4:30PM - 4:42PM |
E5.00006: Two-proton decay correlations in the sd-shell Kyle Brown Neutron knockout reactions from the interaction of a E/A $=$ 57.6 MeV $^{\mathrm{17}}$Ne beam with a $^{\mathrm{9}}$Be target populated levels in $^{\mathrm{16}}$Ne. The correlations between the momenta of the $^{\mathrm{14}}$O$+$p$+$p fragments following two-proton (2p) decay were measured using the charged-particle array HiRA (High Resolution Array). Using correlation data measured for the ground state of $^{\mathrm{16}}$Ne, we were able to test our three-body model for a broad set of parameters. The high statistics and resolution of the data allowed for an unambiguous determination of the effect of the long-range Coulomb interaction on three-body Coulomb decay. The first-excited, J$^{\mathrm{\pi }}=$ 2$^{\mathrm{+}}$ state in $^{\mathrm{16}}$Ne was also populated strongly by neutron knockout. The correlations measured from its 2p decay are quite unusual, displaying aspects of both sequential and diproton-like decay. This unusual behavior is largely reproduced by the three-body model and will also be presented here. [Preview Abstract] |
Saturday, April 11, 2015 4:42PM - 4:54PM |
E5.00007: Searching for isovector signatures in the neutron-rich oxygen and calcium isotopes Wei-Chia Chen, Jorge Piekarewicz We search for potential isovector signatures in the neutron-rich oxygen and calcium isotopes within the framework of a relativistic mean-field theory with an exact treatment of pairing correlations. To probe the isovector sector we calibrate a few relativistic density functionals using the same isoscalar constraints but with one differing isovector assumption. It is found that under certain conditions, the isotopic chain in oxygen can be made to terminate at the experimentally observed ${}^{24}$O isotope. In the case of the calcium isotopes, the drip line is predicted to be reached beyond ${}^{60}$Ca. To produce such behavior, the resulting symmetry energy must be soft, with predicted values for the symmetry energy and its slope at saturation density being $J = (30.92\pm0.47)$ MeV and $L = (51.0\pm1.5)$ MeV, respectively. As a consequence, the neutron-skin thickness of ${}^{208}$Pb is rather small: $R^{208}_{\rm skin} = (0.161\pm0.011)$ fm. This same model, labelled ${\it FSUGarnet}$, predicts $R_{1.4} = (13.1\pm0.1)$ km for the radius of a ``canonical'' 1.4$M_{\odot}$ neutron star, yet is also able to support a two-solar-mass neutron star. [Preview Abstract] |
Saturday, April 11, 2015 4:54PM - 5:06PM |
E5.00008: Deformed suq(2) with deformed Coriolis effect description of superdeformed nuclei in A$\sim$190 region Hamoud Alharbi, Hamad Alhendi, Turki AlOyayd The deformed su$_{q}$(2) model with Coriolis effect is applied to 79 superdeformed bands in the region A$\sim$190. The transition energies and the moments of inertia are calculated within the model and their validity is investigated by comparing them with the experimental data. The effect of deformation of Coriolis effect in the transition energies and the moments of inertia was investigated. A comparison between the su$_{q}$(2) with and without deformed Coriolis effect is made and shows significant improvements in fitting the experimental data. It was shown that deformation of improve the standard deviation of the transition energies up to 80\%. Correlation between the deformation parameter ? and the excesses of neutrons over protons, S, has been observed. This correlation shows a decaying behavior. As a result, the deformation of Coriolis effect becomes weak with the increase of S. [Preview Abstract] |
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