Bulletin of the American Physical Society
2006 73rd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 9–11, 2006; Williamsburg, Virginia
Session BB: Nuclear Physics I |
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Chair: Gerald Feldman, George Washington University Room: Williamsburg Hospitality House Jamestown |
Thursday, November 9, 2006 8:30AM - 8:42AM |
BB.00001: ABSTRACT MOVED TO MB.00009 |
Thursday, November 9, 2006 8:42AM - 8:54AM |
BB.00002: Measurements of the $^1$S$_0$ Scattering Lengths in Neutron-Deuteron Breakup at 19 MeV in a Coincidence Geometry A.S. Crowell, J. Deng, J.H. Esterline, C.R. Howell, M.R. Kiser, R.A. Macri, S. Tajima, W. Tornow, B.J. Crowe III, R.S. Pedroni, W. Von Witsch, H. Wita{\l}a Measurements of the $^1$S$_0$ neutron-neutron ($nn$) and neutron-proton ($np$) scattering lengths, $a_{nn}$ and $a_{np}$ respectively, using neutron-induced deuteron breakup were made at Triangle Universities Nuclear Laboratory (TUNL) at an incident neutron energy of 19.0 MeV. Six liquid scintillator detectors were configured in a coincidence geometry to measure the momenta of the two neutrons in two $nn$ and $np$ final-state-interaction (FSI) pairs while the energy of the proton was determined using a C$_{6}$D$_{12}$ active target. The scattering lengths were extracted from the experimental cross sections by comparison to rigorous three-nucleon calculations using the CD Bonn nucleon-nucleon potential for various values of $a_{nn}$ and $a_{np}$. In this talk results from the two $nn$ and $np$ FSI measurements and the analysis to obtain $a_{nn}$ will be presented. [Preview Abstract] |
Thursday, November 9, 2006 8:54AM - 9:06AM |
BB.00003: Identification of levels in $^{144}$Cs} E.F. Jones, P.M. Gore, Y.X. Luo, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, H.L. Crowell, K. Li, C.T. Goodin, J.O. Rasmussen, S.J. Zhu From the analysis of $\gamma$-$\gamma$-$\gamma$ coincidence data taken with Gammasphere of the prompt $\gamma$ rays in the spontaneous fission of $^{252}$Cf, a cascade of six transitions, at 108.0, 115.1, 263.8, 404.8, 535.2, and tentatively 679.5 keV, was identified in $^{144}$Cs for the first time. The transitions were assigned to a cascade with these energies in $^{144}$Cs from their relative intensities and by identifying their coincidences with the known transitions in $^{105}$Tc and $^{106}$Tc, the 3n and 2n fission partners of $^{144}$Cs, and comparing the Tc intensities to the respective Tc yield tables. The energy levels in $^{138,140,142}$Cs with N = 83, 85, and 87, respectively, just above the spherical closed shell at N = 82, each have first excited states around 10 keV and second excited states between 16 and 65 keV, and no rotational-type bands. These states are associated with single particle states in the spherical region. With N = 89 in $^{144}$Cs, one has crossed the region between N = 88 and 90 where there is a rather sudden change from spherical nuclei with N $\leq$ 88 to significant deformation in N $\geq$ 90 nuclei. The levels in $^{144}$Cs look like a rotational band in a more well-deformed nucleus. [Preview Abstract] |
Thursday, November 9, 2006 9:06AM - 9:18AM |
BB.00004: New Results for the Intensity of Bimodal Fission in Ba Channels of the SF of $^{252}$Cf C.T. Goodin, D. Fong, J.K. Hwang, A.V. Ramayya, J.H. Hamilton, K. Li, Y.X. Luo, J.O. Rasmussen, S.C. Wu, M.A. Stoyer, T.N. Ginter, S.J. Zhu, R. Donangelo, G.M. Ter-Akopian, A.V. Daniel, G.S. Popeko, A.M. Rodin, A.S. Fomichev Triple coincidence data from the fission of $^{252}$Cf were used to deduce the intensity of the proposed ``hot'' mode in Barium channels. $\gamma-\gamma-\gamma$ and $\alpha-\gamma-\gamma$ fission data were analyzed to find the neutron multiplicity distribution for several binary and ternary charge splits. The binary channels Xe-Ru and Ba-Mo were analyzed, as well as the Ba-$\alpha$-Zr, Mo-$\alpha$-Xe, and Te- $\alpha$-Ru ternary channels. An improved method of analysis was used in order to avoid many of the complexities associated with fission spectra. With this method, we were unable to confirm the second mode in either the Ba-Mo or Ba-$\alpha$-Zr splits. [Preview Abstract] |
Thursday, November 9, 2006 9:18AM - 9:30AM |
BB.00005: RHIC and Non-Equilibrium Signals of the Deconfining Phase Transition Alexei Bazavov, Bernd Berg The Relativistic Heavy Ion Collsion (RHIC) experiments carried out at Brookhaven National Laboratory (BNL) provide important information about the formation and dynamical properties of Quark-Gluon Plasma (QGP). Collision of two heavy (about 200 nucleions) nuclei at the center-of-mass energy 200 GeV heats up a spatial volume of $10^3$ fm$^3$ to temperatures at which matter undergoes a phase transition from the hadronic (confined) phase into the plasma (deconfined) phase. At these energies QCD exhibits non-perturbative regime therefore other means than perturbation theory are necessary to study the phenomena. We study the dynamics of the deconfining phase transition by performing Monte Carlo simulations in the Lattice Gauge Theory formalism. We study the response of the system to a rapid temperature quench that mimics initial heating at RHIC. We find that the deconfing phase transition proceeds through the spinodal decomposition scenario. The mechanism slowing down the equilibration of the system is a competition of domains of distinct triality (having different values of the Polyakov loop, an order parameter for pure gauge theory). We measure the structure factors and the gluonic energy and pressure densities and also relate the dynamical growth rates to the Debye screening mass. Strong correlations are found when the system is out of equilibrium but not in the final equilibrium state. [Preview Abstract] |
Thursday, November 9, 2006 9:30AM - 9:42AM |
BB.00006: Monte Carlo Simulation of a Large NaI Detector Using GEANT4 Daniel Mittelberger, Gerald Feldman A Monte Carlo simulation of a high-resolution large-volume NaI detector has been created for the analysis of Compton scattering experiments. This simulation (based on GEANT4) models the components of the detector (a single cylindrical core and four annular quadrants) and its response to a tagged photon beam of variable energy (60-90 MeV), for both in-beam and scattering configurations. The simulation outputs the energy deposited in each component of the NaI to a file for further analysis using the ROOT data analysis package. To more accurately represent the detector lineshape, the output from the simulated in-beam geometry is fitted to experimental in-beam data using a Gaussian smearing function which helps characterize the intrinsic response function of the detector. Once this response function has been determined, the simulation can then be used to model the lineshape for a scattering run from Compton scattering on carbon. With the appropriate lineshape for the scattering geometry and with an analysis of the experimental yields, the differential cross sections for Compton scattering can be extracted from the carbon data taken at MAX-Lab in Lund, Sweden. [Preview Abstract] |
Thursday, November 9, 2006 9:42AM - 9:54AM |
BB.00007: Studying neutron stars at Jefferson Lab: the PRex experiment David S. Armstrong One particularly elusive goal of nuclear structure measurements has been the determination of the radius of the neutron distribution in heavy nuclei. This basic property has yet to be cleanly measured, and a precise determination would have important implications for understanding neutron stars, testing nuclear models, heavy-ion collisions and standard model tests from atomic parity violation. An experiment will take place at Jefferson Lab, which will exploit the fact that the Z$^0$ boson couples primarily to neutrons in order to make a theoretically clean measurement of the neutron radius in $^{208}$ Pb via parity-violating elastic electron scattering. The anticipated precision on the neutron radius is 1\%. The motivation, experimental technique and status of this challenging measurement will be reviewed. [Preview Abstract] |
Thursday, November 9, 2006 9:54AM - 10:06AM |
BB.00008: Equation of State for low density nuclear matter Jutri Taruna, Jorge Piekarewicz Neutron-rich matter at subnuclear densities---present in core-collapse supernovae and the crust of neutron stars---displays fascinating complex structures such as spherical, slablike, and rodlike shapes. The equation of state and the two-body correlation function (both spin dependent and spin independent) are computed via semi-classical Monte-Carlo simulations that incorporate a momentum-dependent two-body potential to simulate Pauli correlations. [Preview Abstract] |
Thursday, November 9, 2006 10:06AM - 10:18AM |
BB.00009: Accelerate the transition of radioisotopes and unwanted weapons-grade $^{239}$Pu into stable nuclei with a system of high frequency modulation for a net energy gain Eugene Pamfiloff A process of high frequency stimulation of nucleons can be utilized for the accelerated fission, decay or controlled transition of unstable isotopes. $^{238}$U could be persuaded to transition promptly into the stable $^{206}$Pb isotope, where a portion of the total mass difference of 29873.802 MeV per nucleus becomes available energy. The proposals of this paper describe an effective system for nuclei stimulation configured to accelerate such a series of 14 transitions over several milliseconds, instead of 4.47 x 10$^{9}$ years. Positive ions or ionized capsules of fuel suspended by magnetic fields and subjected to the system of correlated frequency modulation of multiple beam lines, tailored to the specific target, will emit sufficient energy to stimulate subsequent targets. The system can be applied to all radioisotopes, nuclear waste product isotopes such as $^{239}$Pu, and a variety of other suitable unstable or stable nuclei. Through the proposed confinement system and application of high frequency stimulation in the 10$^{22}$ to 10$^{24}$ Hz regime, the change in mass can be applied to both the fragmentation of subsequent, periodically injected targets, and the production of heat, making a continuous supply of energy possible. The system allows the particle fragmentation process to be brought into the lab and provides potential solutions to the safe disposal of fissile material. [Preview Abstract] |
Thursday, November 9, 2006 10:18AM - 10:30AM |
BB.00010: Proton configuration and mass variations are observed in each of the 3036 isotopes studied. Eugene Pamfiloff The fission and decay transitions of unstable isotopes are studied with particular detailed analysis of nuclei masses, proton - neutron substructure, and the change in mass experienced by individual nucleons of parent, daughter and product isotopes. The data shows the 3036 isotopes studied contain nucleons of a mass unique to each isotope, and further, indicating 3036 proton variations, each differentiated by a distinct mass. Of these, 283 proton variations are further distinguished by belonging to stable benchmark isotopes. The same variations were found with bound neutrons. A direct correlation is observed between the nearest stable benchmark mass and the mass of the nucleon returning to ground state during the transition, indicating a mass dependence to nuclear stability. These findings indicate that a nucleus in an excited state cannot stabilize or return to the ground state until it adjusts mass to match the nearest $Z - N$ and mass per nucleon benchmark. These conclusions were further tested with the analysis of nucleon mass adjustments occurring within the natural and artificial alpha emitter nuclei. The developed system of analysis provided good results when tested against the incident and product particles of high and low energy interactions and events of nuclear transmutation. Every transition to a stable product demonstrates a strong correlation with a specific mass per nucleon benchmark as a third condition of nuclear stability. [Preview Abstract] |
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