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HK: Physik der Hadronen und Kerne

HK 32: Theory V

HK 32.1: Group Report

Wednesday, March 10, 2004, 14:00–14:30, D

Relativistic Quark Model for Light and Strange Baryons — •Robert Ferdinand Wagenbrunn, Katharina Berger, Leonid Glozman, Thomas Melde, Willibald Plessas, and Bianka Sengl — Institut für Theoretische Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, A-8010 Graz

We present new results for baryon properties in a relativistic constituent quark model. The dynamics of the model relies on Goldstone-boson exchange which is motivated by the spontaneous breaking of chiral symmetry of QCD at low energies. With this dynamics the spectra of all light and strange baryons can be reproduced in accordance with experiment [1]. The three-quark Hamiltonian of the model represents an invariant mass operator in relativistic quantum mechanics and it allows for a Poincaré-invariant treatment of hadronic reactions. We have calculated electromagnetic and axial form factors of the nucleons in the point and instant forms [2]. Recently we have extended the approach also to calculating pion-decay widths of N and Δ resonances [3]. In all instances one observes large relativistic effects, what puts considerable doubts on any nonrelativistic quark model.

[1] L.Ya. Glozman et al., Phys. Rev. D 58, 094030 (1998).

[2] R.F. Wagenbrunn et al., Phys. Lett. B 511, 33 (2001); L.Ya. Glozman et al., Phys. Lett. B 516, 183 (2001); S. Boffi et al., Eur. Phys. J. A 14, 17 (2002).

[3] T. Melde et al., Few-Body Syst. Suppl. 14, 37 (2003).