A general formalism is established for constructing models for the photoproduction of mesons from the nucleon. The essential ingredient is a mass operator which describes the coupling between meson-baryon, photon-baryon, and single-baryon channels. The most general forms for the mass operator interactions which produce these couplings are derived. These forms also provide generalizations of the Chew-Goldberger-Low-Nambu amplitudes for pion-nucleon photoproduction to any meson-baryon final state. The models lead to S-matrix elements that transform properly under inhomogeneous Lorentz transformations and are gauge invariant. The photoproduction amplitudes include final state interactions and satisfy Watson's theorem. A specific model is constructed by deriving the mass operator interactions from effective Lagrangians that describe the couplings of mesons, photons, and baryons. The electromagnetic interactions include direct and crossed nucleon contributions, as well as direct contributions from the P 33 ͑1232͒, P 11 ͑1440͒, D 13 ͑1520͒, and S 11 ͑1535͒ resonances. A contact term and exchange terms due to the , , and mesons are also included. The model gives a good fit to the significant multipoles in the energy range from the single-pion, photoproduction threshold up to a center-of-momentum energy of W=1550 MeV, which corresponds to a photon lab energy of 810 MeV.

Abstract.A new electrostatic storage ring for beams at energies up to 30keV. q is currently under 7 development at the National Centre for Mathematics and Physics (NCMP), King Abdulaziz City for Science 8 and Technology (KACST). The ring design is based on the existing electrostatic storage rings, but stretches 9 significantly beyond them in that it shall form the core of a unique flexible experimental facility at KACST. 10The lattice of this ring has been designed in a way that enables the use of state-of-the-art experimental 11 methods to study electron-ion, laser-ion, and ion-neutral beams interactions.

No abstract

A modified version of the previously proposed exponential model with pairing attenuation for the well deformed even-even nuclei has been applied to predict the energy levels of doubly even actinide nuclei. Satisfactory results are obtained by that model as compared with the experimental results. The backbending phenomena are successfully described and discussed. A further comparison with the main previous models has been undertaken to confirm its validity in the heavy nuclei region.

No abstract