ELECTROWEAK PROPERTIES OF THE NUCLEON IN A CHIRAL CONSTITUENT QUARK MODEL

Results for all elastic electroweak nucleon form factors are presented for the chiral constituent quark model based on Goldstone-boson-exchange dynamics. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. The direct predictions of the model yield a remarkably consistent picture of the electroweak nucleon structure. We present results for the elastic electroweak nucleon observables as a progress report of a more comprehensive programme aiming at a consistent description of the electroweak properties of baryons at low energy. The theoretical context is represented by the chiral Constituent Quark Model (CQM) based on the Goldstone-boson exchange (GBE) quark-quark interaction, that is induced by the spontaneous chiral symmetry breaking in QCD and that accurately reproduces the baryon spectrum of light and strange flavors 1. The dynamics of quarks inside the nucleon is essentially relativistic. Therefore, we have adopted the point-form realization of relativistic quantum mechanics, where the boost generators are interaction-free and make the theory manifestly covariant 2. The electromagnetic photon-quark interaction is assumed point-like, but in point-form the momentum delivered to the nucleon is different from the one delivered to the struck quark; hence, we will name this approach the Point-form Spectator Approximation (PFSA) 3. The quark wave functions deduced from fitting the baryon spectrum are used as input and no further parameter is introduced, since quarks are considered point-like and the point-form allows for an exact calculation of all boosts required by a covariant description. Results have recently been published for electromagnetic 4, axial 5 and pseudoscalar 3 nucleon form factors. They are summarized here