We study theoretically the baryon spectra in terms of a deformed oscillator quark (DOQ) model. This model is motivated by confinement of quarks and chiral symmetry breaking, which are the most important non-perturbative phenomena of QCD. The minimization of the DOQ hamiltonian with respect to the deformation for each principal quantum number results in deformations for the intrinsic states of excited baryonic states.We find that the resulting baryon spectra agree very well with the existing experimental data. The spatial deformation of the baryonic excited states carry useful information on the quark confinement and provide a clue to understand the confining mechanism.
We study all the SU(3) baryonic states known experimentally and identify them in the scheme of the deformed oscillator quark (DOQ) model. The DOQ model is motivated by confinement of quarks and chiral symmetry breaking, which are the most important nonperturbative phenomena of QCD. We find most of the baryonic states fall into the DOQ scheme. We then attempt to study the microscopic origin of the DOQ model using a model of three constituent quarks with two-body interactions. We find, however, that such a simple treatment is not able to produce the large deformation effect. We argue then that the confinement caused by the gluon dynamics is essentially important for the deformed baryons. * )
We study electromagnetic transitions of excited baryons in a deformed oscillator quark model, where baryon excited states are described as rotational bands of deformed intrinsic states. We describe all necessary tools to compute transition amplitudes in multipole basis, which are then related to the commonly used helicity amplitudes. We pay a special attention on the sign of the amplitudes as well as their absolute values by computing the photon and pion couplings simultaneously. We have found that the effect of deformation on the transition amplitudes is rather weak. The difficulty in reproducing the empirical amplitude of the Roper state is discussed.
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