118377663
Transverse Charge Densities
Electromagnetic form factors have long been used to probe the underlying charge and magnetization densities of hadrons and nuclei. Traditional three-dimensional Fourier transform methods are not rigorously applicable for systems with constituents that move relativistically. The use of the transverse charge density is a new, rigorously defined way to analyze electromagnetic form factors of hadrons. This review is concerned with the following issues: what a transverse charge density is, how one is extracted from elastic scattering data, the existing results, its relationship with other observable quantities, and future prospects.
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.
121002493
Angle transformation for the $pi$-nucleus optical potential
The transformation of the $\ensuremath{\pi}$-nucleon $T$ matrix from the $\ensuremath{\pi}$-nucleon to the $\ensuremath{\pi}$-nucleus center-of-mass systems is investigated. The correct angle transformation is presented, and it is shown to yield straightforward corrections to the usual Kisslinger and local Laplacian potentials consisting of terms proportional to ${\ensuremath{\nabla}}^{2}\ensuremath{\rho}$ and ${\ensuremath{\nabla}}^{4}\ensuremath{\rho}$ where $\ensuremath{\rho}$ is the target density. Numerical results are presented for ${\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{-}^{12}\mathrm{C}$ elastic scattering at 120- and 180-MeV lab kinetic energy.
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
124010588
Pionic Corrections in the MIT Bag Model
119233886
On the origin of gravitational Lorentz covariance
We provide evidence that general relativity (GR) is the unique spatially covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of GR, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector.
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.
121788713
Nuclear resonance excitation by synchrotron radiation
We have excited the 14-keV level of the Fe/sup 57/ nucleus using synchroton radiation, and observed the conversion electrons emitted in the decay of that state. We believe this to be the first observation of nuclear excitation via synchrotron-produced x rays.