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
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.
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.
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.
120464871
Deuteron photodisintegration: Impulse approximation and gauge invariance
We study the question of whether calculations of deuteron photodisintegration respect gauge invariance, and show that the impulse approximation is in severe disagreement with gauge invariance. The method in which Siegert's theorem is implemented is consistent with gauge invariance to within ten percent. We introduce a modification of the impulse approximation in which the current is conserved exactly. For deuteron photodisintegration this method yields essentially the same results as that of Partovi. Our method can easily be applied to electron- or neutrino-nucleus scattering.
7944762
Towards a Cosmological Dual to Inflation
We derive all single-field cosmologies with unit sound speed that generate scale invariant curvature perturbations on a dynamical attractor background. We identify three distinct phases: slow-roll inflation; a slowly contracting adiabatic ekpyrotic phase, described by a rapidly-varying equation of state; and a novel adiabatic ekpyrotic phase on a slowly expanding background. All of these yield identical power spectra. The degeneracy is broken at the 3-point level: unlike the nearly gaussian spectrum of slow-roll inflation, adiabatic ekpyrosis predicts large non-gaussianities on small scales.
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.
121623246
Semiconductor Particle Detectors
The operation, properties, and fabrication of semiconductor detectors are reviewed. Materials other than Ge and Si are mentioned only briefly. The electronics involved in use of semiconductors as particle detectors is discussed. Application and possible applications to the following are summarized: nuclear reaction chargedparticle spectroscopy, particle identification, mosaics and special structures, alpha -particle spectroscopy, fission studies, neutron spectroscopy, BETA spectroscopy, gamma spectroscopy, detection of minimum- ionizing particles, low-temperature physics, space vehicles, industry, and medicine.