Results 1 - 10 of 1420
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[en] Full text : In any event it is proved that a description of collective states in terms of a SU(6) model might be appropriate, especially in the two limiting situations in which the approximate symmetries O+(5) and SU(3) occur. For nuclei whose spectrum is not too far from these exact symmetries it might be useful to use the respective unperturbed wave functions and energies. The symmetry structure of the nuclear many body system is in general very complex. However, since only few degrees of freedom play a dominant role in the description of the collective states, it is hoped that the Hamiltonian of the system when written in terms of these degrees of freedom has simple symmetry properties. It is important to notice that our collective Hamiltonian yields a finite energy matrix for a given value of N and a definite spin. This is a consequence of the symmetry properties of our collective operators. Because the boson-boson interaction in Hamiltonian splits the degeneracy of the multiplets, this limit describes an anharmonic vibrator. It is worth nothing that the knowledge of the invariance properties of the Hamiltonian provides directly a solution to the eigenvalue problem.
[en] The quark model is reviewed briefly for baryons and the various versions of SU(6) symmetry which were proposed and used in connection with baryon spectroscopy are reviewed. A series of basic questions are reviewed which experimental work in this field should aim to settle, as a minimal program. One also heralds the beginning of a new baryon spectroscopy associated with psi physics
[en] The spin structure of the nucleon is investigated in a model in which the constituent quarks of the SU(6) scheme of hadrons have internal parton structure. It is shown that SU(6) mixing in the nucleon wave function is important for the nucleon spin distribution. The polarized parton distributions are calculated, and predictions for gn1(x) are given. Owing to SU(6) mixing, the spin asymmetry of the neutron turns out to be considerably larger than the predictions of other models. 22 refs., 3 figs
[en] A systematic approach to even-even, odd-even, and odd-odd nuclei, based on spherical quadrupole phonons, is discussed. The truncated quadrupole-phonon model (TQM), based on SU(6) symmetry, describes even-even nuclei in the collective approximation. In the particle-TQM interaction model (PTQM), an odd single particle is coupled to the TQM core. In the SU(number) limit of the PTQM, analogs of Nilsson states appear. In the cluster-vibration model, even-even, odd-even, and odd-odd nuclei are described by coupling a few selected shell-model single particles to the quadrupole vibration (harmonic or TQM). The quasicluster-vibration model (QCVM) is an approximation of the CVM in the sense that the cluster consists of a few quasiparticles. Both the diagonalization and the diagrammatic approaches are discussed. The latter leads to generalized vibrational rules (GVR), as a consequence of the nuclear Ward identity. 106 references, 2 tables
[en] The essential ingredients of various SU(6)sub(W) models for Baryon resonance decays are briefly reviewed. Their predictions for the [70,1-] and [56,2+] supermultiplets are then compared with data on π, rho and photon transitions, with emphasis on new results (or non-results) from the past year or so. Candidates for other possible SU(6) supermultiplets are then discussed together with the methods of making such assignments. Some conclusions are offered. (author)