München 2006 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 18: Theorie

HK 18.1: Vortrag

Dienstag, 21. März 2006, 14:00–14:15, B

Chiral Dynamics of Baryons in a Lorentz Covariant Quark Model — •Valery Lyubovitskij, Amand Faessler, Thomas Gutsche, and Kem Pumsa-ard — Institute of Theoretical Physics, Tuebingen University, Auf der Morgenstelle 14, 72076 Tuebingen, Germany

We develop a manifestly Lorentz covariant chiral quark model for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons [1,2]. The approach is based on a non-linear chirally symmetric Lagrangian, which involves effective degrees of freedom - constituent quarks and the chiral (pseudoscalar meson) fields. In a first step, this Lagrangian can be used to perform a dressing of the constituent quarks by a cloud of light pseudoscalar mesons and other heavy states using the calculational technique of infrared dimensional regularization of loop diagrams. We calculate the dressed transition operators with a proper chiral expansion which are relevant for the interaction of quarks with external fields in the presence of a virtual meson cloud. In a second step, these dressed operators are used to calculate baryon matrix elements. Applications are worked out for the masses of the baryon octet, the meson-nucleon sigma terms, the magnetic moments of the baryon octet, the nucleon charge radii, the strong vector meson-nucleon couplings and the full momentum dependence of the electromagnetic form factors of the nucleon.

[1] A. Faessler, T. Gutsche, V.E. Lyubovitskij, K. Pumsa-ard, Prog. Part. Nucl. Phys. 55, 12 (2005). [2] A. Faessler, T. Gutsche, V.E. Lyubovitskij, K. Pumsa-ard, hep-ph/0511319.