We present a new classification scheme of baryon ground states and resonances into SUð3Þ flavor multiplets. The scheme is worked out along a covariant formalism with relativistic constituent quark models and it relies on detailed investigations of the baryon spectra, the spin-flavor structure of the baryon eigenstates, the behavior of their probability density distributions as well as covariant predictions for mesonic decay widths. The results are found to be quite independent of the specific types of relativistic constituent quark models employed. It turns out that a consistent classification requires one to include also resonances that are presently reported from experiments with only two-star status.

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We report on a study of π and η decays of strange baryon resonances within relativistic constituentquark models based on one-gluon-exchange and Goldstone-boson-exchange dynamics. The investigations are performed in the point form of Poincaré-invariant relativistic quantum mechanics with a spectator-model decay operator. The covariant predictions of the constituent-quark models underestimate the experimental data in most cases. These findings are congruent with an earlier study of nonstrange baryon decays in the light-flavor sector. We also consider a nonrelativistic reduction of the point-form spectator model, which leads to the decay operator of the elementary emission model. For some decays the nonrelativistic results differ substantially from the relativistic ones and they exhibit no uniform behavior as they scatter above and below the experimental decay widths.

We address the construction of transition operators for electromagnetic, weak, and hadronic reactions of relativistic few-quark systems along the spectator model. While the problem is of relevance for all forms of relativistic quantum mechanics, we specifically adhere to the point form, since it preserves the spectator character of the corresponding transition operators in any reference frame. The conditions imposed on the construction of point-form spectator-model operators are discussed and their implications are exemplified for mesonic decays of baryon resonances within a relativistic constituent quark model. PACS. 12.39.Ki Relativistic quark model -13.30.Eg Hadronic decays -21.45.+v Few-body systems

We present a microscopic derivation of the form factors of strong-interaction πN N and πN ∆ vertices within a relativistic constituent quark model. The results are compared with form factors from phenomenological meson-baryon models and recent lattice QCD calculations. We give an analytical representation of the vertex form factors suitable for applications in further studies of hadron reactions. Understanding the meson-baryon strong-interaction vertices has been a hard and long-standing problem. Attempts to derive a microscopic explanation, desirably on the grounds of QCD, have not yet led to conclusive results. The problem is of considerable importance not only in particle but also in nuclear physics. Practically all realistic meson-exchange N N potentials, 3N forces, and πN dynamical models rely on certain inputs for strong form factors. Mostly they have been based on phenomenological arguments and one has usually employed monopole or dipole parametrizations with cut-off parameters fitted to experiment. Different parametrizations have big influences, e.g., on meson-baryon dynamical models (see Refs. [1,2,3,4,5,6]), on N N potentials often used in present-day nuclear calculations (e.g., the Nijmegen [7,8,9], Bonn [10,11,12], and Argonne [13, 14] potentials), and on 3N forces, see, e.g., refs. [15,16]. Consequently, a microscopic derivation of the meson-baryon interaction vertices constitutes an important problem and it has long and often been asked for (see, e.g., Refs. [17,18]).The uncertainty about the meson-baryon strong-interaction vertices has even been increased by the recent advent of lattice QCD calculations [19,20]. These works have led to results different among each other and partly distinct from earlier lattice QCD calculations by Liu et al. [21,22]. Lattice QCD results are furthermore at variance with form factors adopted so far in relativistic models of meson-baryon dynamics [4,5,6].Here, we perform a microscopic derivation of the strong meson-baryon form factors on the basis of a relativistic constituent quark model (RCQM). It is free of any phenomenological input (fit parameters), and the form-factor dependence on the relativistic four-momentum transfer Q 2 is directly predicted from the RCQM, which has already been successful in reproducing the invariant mass spectrum of baryons [23,24] and the electroweak structure of the nucleons and other baryon ground states [25,26,27,28,29]. The same RCQM has recently been employed in a covariant study of the mesonic decays of baryon resonances [30,31,32] leading to results for partial decay widths qualitatively rather different from previous nonrelativistic or relativized studies. The systematics found in the relativistic decay widths for all the π, η, and K decay modes has subsequently also led to a partly new classification of baryon resonances into flavor multiplets [33,34].In this paper we consider the πN N and πN ∆ form factors according to the process depicted in Fig. 1(a) and described by the matrix elements of the hadronic interaction Lagrangianw...

We present a study of the electromagnetic structure of the nucleons with constituent quark models in the framework of relativistic quantum mechanics. In particular, we address the construction of spectator-model currents in the instant and point forms. Corresponding results for the elastic nucleon electromagnetic form factors as well as charge radii and magnetic moments are presented. We also compare results obtained by different realistic nucleon wave functions stemming from alternative constituent quark models. Finally, we discuss the theoretical uncertainties that reside in the construction of spectator-model transition operators.Comment: 13 pages, 9 figures, updated and extended version for publicatio

We present results for kaon decay widths of baryon resonances from a relativistic study with constituent quark models. The calculations are done in the point-form of Poincare-invariant quantum mechanics with a spectator-model decay operator. We obtain covariant predictions of the Goldstone-boson-exchange and a variant of the one-gluon-exchange constituent quark models for all kaon decay widths of established baryon resonances. They are generally characterized by underestimating the available experimental data. In particular, the widths of kaon decays with increasing strangeness in the baryon turn out to be extremely small. We also consider the nonrelativistic limit, leading to the familiar elementary emission model, and demonstrate the importance of relativistic effects. It is found that the nonrelativistic approach evidently misses sensible influences from Lorentz boosts and some essential spin-coupling terms.Comment: 6 pages, 3 table

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