120771825
The neutron electric dipole moment in the cloudy bag model
Abstract An evaluation of the neutron electric dipole moment (NEDM), using the cloudy bag model (CBM) shows that two CP -violating effects (a quark mass term and a pion-quark interaction) have contributions that are about equal in magnitude, but opposite in sign. This cancellation allows the upper limit on the θ parameter to increase by about an order of magnitude.
16251254
Light front nuclear physics: Mean field theory for finite nuclei
A light-front treatment for finite nuclei is developed from a relativistic effective Lagrangian (QHD1) involving nucleons, scalar mesons and vector mesons. We show that the necessary variational principle is a constrained one which fixes the expectation value of the total momentum operator P + to be the same as that for P − . This is the same as minimizing the sum of the total momentum operators: P − + P + . We obtain a new light-front version of the equation that defines the single nucleon modes. The solutions of this equation are approximately a non-trivial phase factor times certain solutions of the usual equal-time Dirac equation. The ground state wave function is treated as a meson-nucleon Fock state, and the meson fields are treated as expectation values of field operators in that ground state. The resulting equations for these expectation values are shown to be closely related to the usual meson field equations. A new numerical technique to solve the self-consistent field equations is introduced and applied to 16 O and 40 Ca. The
356245
Current algebra and the cloudy-bag model.
Two versions of the cloudy-bag model (surface and volume coupling) satisfy the commutation relations of current algebra. Perturbation-theory evaluations of various observables are compared for the two treatments. The electromagnetic properties are essentially the same in both versions. The volume-coupling model contains, in lowest order, a pion-quark contact interaction that contributes to the axial-vector current. Including the effect of this term leads to a computed value of g/sub A/ of about 1.25, if the radius of the nucleon bag is around 1.0 fm.
122904929
Isobar dynamics and pion-nucleus elastic scattering
Abstract A new formalism is developed for studying pion-nucleus scattering in a model which takes into account the dynamics of the (3, 3) pion-nucleon resonance, or Δ isobar. This treatment is used to calculate π + elastic scattering from 16 O, 40 Ca, 48 Ca and 208 Pb at energies from 114 to 240 MeV. Some results for π − elastic scattering are also given. From fits to π + scattering data it is found that the Δ-nucleus interaction is well described by a spherical local complex potential proportional to the nuclear density. The central strength of this potential depends on energy but not on nuclear mass number. Some difficulties in determining the parameters of this potential from elastic scattering are discussed.
124010588
Pionic Corrections in the MIT Bag Model
18765682
Quark-meson coupling model for finite nuclei.
A Quark-Meson Coupling (QMC) model is extended to finite nuclei in the relativistic mean-field or Hartree approximation. The ultra-relativistic quarks are assumed to be bound in non-overlapping nucleon bags, and the interaction between nucleons arises from a coupling of vector and scalar meson fields to the quarks. We develop a perturbative scheme for treating the spatial nonuniformity of the meson fields over the volume of the nucleon as well as the nucleus. Results of calculations for spherical nuclei are given, based on a fit to the equilibrium properties of nuclear matter. Several possible extensions of the model are also considered.
37692138
Dirac-Born-Infeld genesis: an improved violation of the null energy condition.
We show that the Dirac-Born-Infeld conformal galileons, derived from the world-volume theory of a 3-brane moving in an anti-de Sitter bulk, admit a background, stable under quantum corrections, which violates the null energy condition. The perturbations around this background are stable and propagate subluminally. Unlike other known examples of null energy condition violation, such as ghost condensation and conformal galileons, this theory also admits a stable, Poincaré-invariant vacuum. The 2 → 2 amplitude satisfies standard analyticity conditions. The full S matrix is likely not analytic, however, since perturbations around deformations of the Poincaré invariant vacuum propagate superluminally.
111136184
An Improved Control System for Van De Graaff Accelerators
In an effort to improve the energy stability and operating convenience of the Rutgers-Bell FN Tandem, a study has been made of the processes involved in the standard Van de Graaff corona stabilization system. In the light of these observations, a terminal voltage control system has been designed using error signals derived both from the slit system and the capacity pickoff plates. The system operates using either the standard slit system, or the machines' Generating Voltmeter as the terminal voltage reference, switching automatically to the G. V. system when beam is lost for any reason.
199082345
Search for X-ray induced decay of the 31-yr isomer of 178Hf using synchrotron radiation
Isomeric {sup 178}Hf (t{sub 1/2} = 31 yr, E{sub x} = 2.446 MeV, J{sup {pi}} = 16{sup +}) was bombarded by a white beam of x-rays from the Advanced Photon Source at Argonne National Laboratory. A search was made for x-ray induced decay of the isomer by detecting prompt and delayed {gamma} rays associated with the decay. No induced decay was observed. Upper limits for such a process for x-ray energies between 7-100 keV were set. The limits between 7 and 30 keV are below {approx} 3 x 10{sup -27} cm{sup 2}-keV for induced decay that bypasses the 4-s isomer and {approx} 5 x 10{sup -27} cm{sup 2}-keV for induced decay that is delayed through this isomer, orders of magnitude below values at which induced decay was reported previously. These limits are consistent with what is known about the properties of atomic nuclei.