[en] We present an algebraic description of the geometric structure of baryons in terms of the algebra U(7). We construct a mass operator that preserves the threefold permutational symmetry and discuss a collective model of baryons with the geometry of an oblate symmetric top. This model is applied to the mass spectrum and the photocoupling amplitudes of nonstrange baryons. (author)

[en] Short communication

[en] Some of the history behind the form of the wavefunctions of the nucleon and the delta in models of hadron structure is briefly reviewed. The possibility of D-state admixture and its magnitude is analyzed. Moreover the dynamical origin of such admixture and its observable consequences are investigated. Finally comments are given about some recent data analysis. 19 refs.; 1 table

[en] In this paper, the chiral bag models pioneered by Gerry Brown and his collaborators are used to discuss the following questions: 1. Why is the position of the Δ resonance almost unmodified in heavy nuclei? 2. Is the phenomenology of the chiral pion coupling to quarks consistent with experiment? In particular, does it predict reasonable coupling constants, pion decay constant, and pion field energy? 13 refs.; 2 figs

[en] Simple arguments are given for the explanation of the gross structure of the spectrum of hadron and dibaryon resonances based on the Bohr quantization rule and the correspondence principle. 18 refs.; 2 figs.; 10 tabs

[en] Bloom-Gilman duality demonstrates empirically that the electroproduction of N*'s at low momentum transfers averages smoothly around the scaling curve measured at large momentum transfers. The latter is proportional to the sum of the squares of the constituent charges whereas the former involves the coherent excitation of resonances and is driven by the square of summed constituent charges. We determine the minimal necessary conditions for this equality to be realized so that duality can occur and consider the implications for a range of processes that may be studied soon at CEBAF

[en] In order to subtract the spurious centre-of-mass motion effect from the prediction of the static MIT bag model for a spin-3/2 hadron, we solve the Rarita-Schwinger equation for a particle in an infinite square potential well. The correction to the mass of such a particle turns out to be quite similar to that found previously for baryons of spin 1/2. (author)

[en] We present first results for masses of positive and negative parity excited baryons in lattice QCD using an O(a²) improved gluon action and a Fat Link Irrelevant Clover (FLIC) fermion action in which only the irrelevant operators are constructed with fat links. The results are in agreement with earlier calculations of N* resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner, even for the Wilson fermion action. The results also indicate a splitting between the lowest J^P=1/2^- states for the standard nucleon interpolating fields

[en] Eta photoproduction on the nucleon is studied in a model containing baryon resonances, nucleon Born terms and t-channel vector meson exchange and is compared to existing data. In nuclear application we present differential cross sections for d, ³He, ³H and ⁴He. In particular photoproduction on the deuteron and ³He will be ideal in order to study the elementary reaction on the neutron and subsequently the isoscalar excitation of the S₁₁ (1535) resonance. (author)

[en] The excitation of the Δ-resonance on the free nucleon is discussed. The main interest is on how to properly define and extract from experimental data the Δ-parameters and coupling constants. 14 refs