Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session BK: Nuclear Theory I |
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Sponsoring Units: DNP JPS Chair: Hiroshi Toki, RCNP Osaka University Room: Ritz-Carlton Hotel Maui |
Monday, September 19, 2005 7:00PM - 7:15PM |
BK.00001: A Mechanism for Formation of Narrow Hadronic Resonances Naftali Auerbach, Vladimir Zelevinsky, Alexander Volya The observation of a narrow peak around the energy of 1540 MeV in the K+N system has caused considerable excitement and research activity. It was suggested that the observed peak represents a pentaquark resonance, the theta particle. Since this initial discovery many different experiments (about 10) have found the peak around this energy. However, in about the same number of experiments (usually using higher energy probes) the theta was not seen. Moreover, the experiments that do observe the theta peak often differ in the energy position of the resonance. The determination of the widths is difficult because of experimental limitations. Indirect considerations suggest that the width is smaller than 1 MeV. Altogether the state of the art in this field is waiting for data of better quality. In this work we discuss a mechanism that could produce narrow resonances due to interference effects. The mechanism suggested by authors in Phys. Lett. B 590 (2004) 45 is of generic nature and can accommodate various models for the states involved. The central point is that since one deals with a many-quark system a large number of many-body states can be formed which interact via various mechanisms including interference through decay. As a result of this interaction a number of narrow states is generated, superimposed on a very wide resonance(s) which makes up the background. This is similar to the formation of giant resonances in nuclear physics. [Preview Abstract] |
Monday, September 19, 2005 7:15PM - 7:30PM |
BK.00002: Relativistic Three-Body Equations in a Wavelet Basis Wayne Polyzou, Fatih Bulut We show how to use Daubechies' wavelets to reduce the relativistic Faddeev-Lovelace equations to approximate linear equations with sparse matrices. We transform the equations to a form where the spectator and two-body relative momenta are separated. We use the renormalization group equation for the scaling basis functions [1][2] to accurately and efficiently compute scaling basis matrix elements of the transformed three-body kernel with moving singularities. The wavelet transform provides a fast (O(N)) mapping from the scaling basis to the wavelet basis, where the kernel can be accurately approximated by a sparse matrix. \newline [1] B. Kessler, G. L. Payne, W. N. Polyzou, Phys. Rev. C70,034003(2004). \newline [2] B. M. Kessler, G. L. Payne, W. N. Polyzou Few-Body Systems, 33,1(2003). [Preview Abstract] |
Monday, September 19, 2005 7:30PM - 7:45PM |
BK.00003: The Electric Dipole Form Factor of the Nucleon Claudio Maekawa, William Hockings, Bira van Kolck Various experiments have attempted to determine if the neutron has a non zero electric dipole moment (EDM). Because this quantity is relatively insensitive to the CKM phase, its observation is likely to represent an effect from other CP- violating quark interactions. The $\bar{\theta}$ term in QCD, in particular, induces T-odd contributions from the pion cloud to the nucleon EDM. The associated electric dipole form factor (EDFF) is not as readily accessible experimentaly, but it is useful in that it gives an important electromagnetic contribution to nuclear Schiff moments, to which atomic effects are sometimes sensitive. We calculate the nucleon EDFF in the model- independent framework of chiral perturbation theory, up to subleading order. We also discuss implications for the deuteron EDM. [Preview Abstract] |
Monday, September 19, 2005 7:45PM - 8:00PM |
BK.00004: The T-Violating Effective Chiral Lagrangian William Hockings, Ubirajara van Kolck At quark level, there are numerous sources of T violation that generate T-odd interactions among hadrons, with the form of the interactions determined by the chiral symmetry properties of the sources. These sources include the QCD $\bar{\theta}$ term, the quark electric and chromoelectric dipole moments, and other terms that are formally of dimension six and higher. We present a method to construct the corresponding T-violating effective chiral Lagrangian, in which we eliminate by field redefinitions the terms that would lead to vacuum instability. As an illustration of the uses of this Lagrangian, we present a calculation of the electric dipole form factor of the nucleon in leading order in an expansion in powers of momenta and quark masses. [Preview Abstract] |
Monday, September 19, 2005 8:00PM - 8:15PM |
BK.00005: UCN scattering on nano-size targets Vladimir Gudkov The elastic scattering cross section of ultra-cold neutrons (UCN) on a target (sphere or a bubble in liquid helium) of a nanometer size scale is calculated. Depending on neutron energy and on the size of the target, the scattering of this system can be described by three different scattering regimes. As a consequence, UCN scattering can manifest low-energy, intermediate energy and high energy behavior in terms of a conventional description in collision theory. It is shown that UCN scattering on a nano-size target can have a resonance dependence on the size of the target. Also, under special conditions, the scattering process of UCN has a coherent nature which leads to a significant increase in the value of the cross section. [Preview Abstract] |
Monday, September 19, 2005 8:15PM - 8:30PM |
BK.00006: Density Profile of Asymmetric Two-component Fermionic Systems at Infinite Scattering Length Thomas Luu, Joseph Carlson, Sanjay Reddy We investigate the properties of asymmetric two-component fermionic systems at strong coupling ($k_fa=\infty$). Density profiles of these systems are calculated at the Thomas-Fermi level. We show that the height of the discontinuity between the superfluid phase and normal phase can be influenced by the value of $\xi$, the proportionality constant in the universal regime. Such a relationship may prove useful in experimentally determining $\xi$. Also, we calculate the specific heat of such systems. [Preview Abstract] |
Monday, September 19, 2005 8:30PM - 8:45PM |
BK.00007: Microscopic approach to isospin-asymmetric nuclear matter: recent progress and applications. Francesca Sammarruca, Plamen Krastev We will present and discuss a variety of recent results from our on-going investigation of effective interactions in dense, isospin-asymmetric hadronic environment within the Dirac-Brueckner-Hartree-Fock framework. These include microscopic isospin-dependent in-medium nucleon-nucleon cross sections, a crucial information for predicting the nucleon mean free path in nuclear matter and thus nuclear transparency. Two-body in-medium cross sections are also useful for transport model simulations of heavy-ion collisions, with asymmetry considerations being especially of interest at this time due to the possibility to study collisions of neutron-rich nuclei at RIA energies. Our work in progress extends to neutron star properties and spin polarized neutron matter. [Preview Abstract] |
Monday, September 19, 2005 8:45PM - 9:00PM |
BK.00008: Quantum Monte Carlo Lattice Simulation of Thermal Properties of Low-Density Neutron Matter Takashi Abe, Ryoichi Seki Thermal properties of low-density neutron matter are investigated by nuclear many-body simulation on three-dimensional cubic lattice. Determinantal quantum Monte Carlo calculations are carried out for the Hamiltonian with a coupling constant of the neutron-neutron interaction determined from effective field theory. Method of finite-size scaling is applied to extract thermodynamical information. Phase diagram shows that low-density neutron matter undergoes a phase transition from a superfluid state to normal, as the temperature or the density increases. The results are also compared with the existing mean-field and related calculations. [Preview Abstract] |
Monday, September 19, 2005 9:00PM - 9:15PM |
BK.00009: Novel phases of color superconductivity Jeffrey Bowers Cold dense quark matter is a color superconductor. QCD favors Cooper pair that are antisymmetric in flavor, but at densities relevant for compact stars, charge neutrality and the heaviness of the strange quark together imply unequal number densities (and Fermi surfaces) for the different quark flavors. Novel phases have been proposed that accomodate pairing between the mismatched Fermi surfaces. These include homogeneous and isotropic Sarma (``gapless'') phases, in which the Fermi sphere occupation is redistributed to allow pairing, and inhomogeneous and anisotropic Larkin-Ovchinnikov-Fulde-Ferrrell (LOFF) phases, in which Cooper pairs acquire nonzero total momentum. I investigate the stability of the Sarma phase when it is subjected to a small LOFF fluctuation, i.e. a small spatial variation of the order parameter, with a concomitant charge density wave. These fluctuations lower the free energy of the system when the Coulomb energy of the charge density wave is sufficiently small. [Preview Abstract] |
Monday, September 19, 2005 9:15PM - 9:30PM |
BK.00010: Confinement Theory for Hadrons Carl Case A dynamic relationship is proposed that leads to chiral symmetry breaking for massless quarks and in cancellation of the color electric field leaving only color magnetic fields acting on hadron quarks. Color superconducting states result giving rise to a color Meissner effect. Quarks are trapped within the color magnetic fields and quantized color magnetic flux bundles are trapped by circulating quarks creating quark-gluon composites that gain mass. The flux quantization introduces a topological defect that generates collective quark-gluon composite energy states corresponding to the various quark flavors. Topological winding numbers serve as quantum numbers for the quark flavors. Up and Down states correspond to a winding number of 1. Strange/ Charm and Bottom/ Top states correspond respectively to winding numbers of 2 and 3 respectively. The Dirac equation is solved using the Hartree self-consistent field method and the Born approximation. Resulting mass spectra calculations are presented for 30 baryons, 20 mesons and for the proton-neutron mass difference. . [Preview Abstract] |
Monday, September 19, 2005 9:30PM - 9:45PM |
BK.00011: Applications of Effective Operators within the NCSM Bruce R. Barrett, Ionel Stetcu, Calvin W. Johnson, Petr Navratil, James P. Vary The no-core shell model (NCSM) is a powerful many-body method which provides the solution to the Schr\"odinger equation for $A$ interacting nucleons in a restricted space. Starting from realistic nucleon-nucleon interactions that accurately fit the experimental phaseshifts, we use a unitary transformation approach to obtain an effective interaction in the model space (realistic three-nucleon forces can be also implemented, but we restrict the discussion to two-body forces). The same renormalization procedure can be applied to other operators, obtaining results consistent with the NCSM wave functions. In our presentation we will discuss renormalization of short- and long-range operators, as well as the latest applications of the NCSM to the description of ground- and excited-state properties. I.S. and B.R.B acknowledge partial support by NFS grants PHY0070858 and PHY0244389. The work was performed in part under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. P.N. received support from LDRD contract 04-ERD-058. J.P.V. acknowledges partial support by USDOE grant No DE-FG-02-87ER-40371, and C.W.J. acknowledges USDOE grant No.DE-FG02-03ER41272 . [Preview Abstract] |
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