Volume 29, Issue 6, November 1998
29(1998); http://dx.doi.org/10.1134/1.953090View Description Hide Description
The aim of this review is to present an approach to unitary models that has been developed during the last ten years. The approach uses wave functions and operators defined in Fock–Bargmann space. A solution for the shell model is introduced, as well as some extensions that are related to a classical treatment of theory.
29(1998); http://dx.doi.org/10.1134/1.953091View Description Hide Description
The change of the structure of low-lying excited states of even–even spherical nuclei in going from closed-shell to transitional nuclei is studied using the quasiparticle–phonon model. The transition charge densities of these states and the distribution of electromagnetic transition strengths are investigated for excitation energies of up to 5 MeV. The properties of low-lying states and states forming pygmy resonances are analyzed. The anomalous behavior of the photoexcitation cross sections of isomers in odd nuclei is explained. The theoretical results are compared to the available experimental data.
29(1998); http://dx.doi.org/10.1134/1.953092View Description Hide Description
The theoretical approaches to the description of backward elasticscattering at energies 0.5–2 GeV are reviewed. In addition to the mechanisms of neutron exchange and single scattering, the role of -isobar exchange is studied using the six-quark model for the vertex. Relativistic effects are taken into account within the Hamiltonian dynamics of systems with a fixed number of particles. The important role of Glauber rescatterings in the initial and final states in the neutron-transfer mechanism is displayed. Special attention is paid to the mechanism of Δ-isobar excitation, which, despite the large momentum transfer, is rather weakly sensitive to the high-momentum components of the deuteron wave function and dominates at incident protonenergies The reaction is studied in the Δ-resonance region in order to determine the parameters of the amplitudes for transitions needed to calculate the Δ-isobar contribution to the process It is shown that the amplitude of the Δ-resonance mechanism for the process is very sensitive to the parameters of the and vertex form factors. The role of more exotic mechanisms is briefly discussed.
29(1998); http://dx.doi.org/10.1134/1.953093View Description Hide Description
29(1998); http://dx.doi.org/10.1134/1.953094View Description Hide Description
The evolution and current status of the technique of three-coordinate vertex detectors are reviewed. Data acquisition methods and the recording of the topology of complicated events by means of vertex detectors are discussed, along with the features of such detectors as time-projection chambers, pictorial (jet) chambers, vector drift chambers, and vertex detectors based on straw tubes. Tables of the parameters of the best known gas vertex detectors used in fixed-target and colliding-beam experiments are given.