Relativistic Quark Model Based Description of Low Energy NN Scattering

A description of the NN scattering is constructed starting from the $\pi, \eta, \eta'$ pseudoscalar-, the $\rho, \phi, \omega$ vector-, and the $\varepsilon(600), a_0, f_0(1400)$ scalar - meson-nucleon coupling constants, which we obtain within a relativistic quark model. Working within the Blankenbecler-Sugar-Logunov-Tavkhelidze quasipotential dynamics we thus describe the NN phase shifts in a relativistically invariant way. In this procedure we use the phenomenological form factor cutoff masses and the effective $\varepsilon$ and $\omega$ meson-nucleon coupling constants, only. The comparison of our NN phase shifts to the both empirical data and the Bonn OBEP fit shows good agreement -- the ratio of the $\chi^2$ for the present results to the $\chi^2$ for Bonn OBEP description is 1.2.Comment: 20 LaTeX pages, 2 postscript figures are available on request. Preprint IPSAS-RA-940

Nucleon Properties in the Perturbative Chiral Quark Model

We apply the perturbative chiral quark model (PCQM) to analyse low-energy nucleon properties: electromagnetic form factors, meson-nucleon sigma-terms and pion-nucleon scattering. Baryons are described as bound states of valence quarks surrounded by a cloud of Goldstone bosons (pi, K, eta) as required by chiral symmetry. The model is based on the following guide lines: chiral symmetry constraints, fulfilment of low-energy theorems and proper treatment of sea-quarks, that is meson cloud contributions. Analytic expressions for nucleon observables are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling constant, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our results are in good agreement with experimental data and results of other theoretical approaches.Comment: 8 pages. Invited talk given at Workshop on the Physics of Excited Nucleons "NSTAR2001", Mainz, Germany, March 7-10, 200

Electromagnetic form factors of the baryon octet in the perturbative chiral quark model

We apply the perturbative chiral quark model at one loop to analyze the electromagnetic form factors of the baryon octet. The analytic expressions for baryon form factors, which are given in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor), and the numerical results for baryon magnetic moments, charge and magnetic radii are presented. Our results are in good agreement with experimental data.Comment: 15 pages, 6 figures, to be published in Eur. Phys. J.

Magnetic moments of S-shell pentaquarks in the constituent quark model

We discuss the magnetic moments of the recently discovered exotic baryons Theta(+) and Xi(--) and their multiplet partners in the framework of a naive additive quark model. These baryons are set up as pentaquark states where four quarks and a single antiquark are located in their ground state orbit. The pentaquark states are classified as members of the flavor SU(3) octet and antidecuplet with spin-parity J^P = (1/2)^- and (3/2)^-, where we determine the magnetic moments of these pentaquark states.Comment: 13 pages, 2 figures, elsart; publication version, 8 pages, 1 figure, ptptex; upload miss correcte

Two-photon decay of heavy hadron molecules

We discuss the two-photon decay width of heavy hadron molecules and study the dependence on the constituent meson masses and on the binding energy. In addition finite size effects due to the extended structure of the bound state are shown to have a strong influence on the predictions for this decay width.Comment: 5 pages, 4 figure