On Electroweak Moments of Baryons and Spin-Flavour Structure of the Nucleon

The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static and quasi-static electroweak characteristics of nucleons.The role of nonvalence degrees of freedom, the nucleon sea partons and/or peripheral meson currents, is shown to be important to select and make use of the relevant symmetry parametrization of hadron observables. With our preferable universal value of the SU(3)-symmetry parameter $\alpha_{D}=D/F+D=.58$, taken for both magnetic moments and axial-vector constants entering into the semi-leptonic baryon decays, we obtain the following values for moments $\Delta q$ of the spin-dependent structure function of the proton: $\Delta u \simeq .84(.82), \Delta d \simeq -.42(-.44), \Delta s=-.22 \pm .05 (-.10 \pm .03)$, where the values in parentheses correspond to the widely used "standard" value of $\alpha^{axial}_{D}=.63$. The estimations of the strange sea contributions to the nucleon magnetic moments and rms are also presented.